< : less than.

> : more than.

: greater than or equal to.

: less than or equal to.

Absolute difference: the absolute value of the difference between two variables. For example: (Group A) 2% – (Group B) 1% = 1%.

Acidemia: increased acidity of the blood, which may interfere with normal function of the human body.

Acidosis: in obstetrics, an accumulation of lactic acid in the blood when lack of oxygen causes anaerobic metabolism.

Active phase labor: see labor.

Adjust (for): to adjust for a variable is to try to separate its effect from the treatment effect, so it will not confound with the treatment. (See confounding.)

Aggregate score (aggregate variable): a value calculated from data obtained by sets of diverse measurements. For example, researchers may calculate an aggregate score combining the incidence of multiple types of rare neonatal outcomes in order to increase the power of the study to detect significant differences between groups.

Ambulate: to walk.

Amniotic fluid embolism (AFE): a rare condition in which amniotic fluid or fetal cells enter the maternal bloodstream and trigger an overwhelming, often fatal, allergic reaction.

Amniotic fluid index (AFI): the score (expressed in centimeters) given to the amount of amniotic fluid seen on ultrasound in the pregnant uterus. To determine the AFI, an ultrasound is done of the uterus using a four-quadrant technique. The deepest, unobstructed (no fetal parts or umbilical cord present), vertical length of each pocket of fluid is measured in each quadrant and then added up with the others. A normal AFI score is greater than 5 cm and less than 20 cm.

Amnionitis: inflammation of the amniotic sac. See also chorioamnionitis.

Amniotomy: artificial rupture of membranes.

Anal incontinence: see incontinence, anal.

Analgesia: pain relief.

Anesthesia: loss of sensation.

Anoxia: lack or almost complete lack of oxygen, sometimes also used to describe a moderate decrease in oxygen, which is more properly called hypoxia.

Antepartum: prior to labor.

Anterior position: see cephalic presentation.

Antiemetic: a medication or treatment preventing or arresting vomiting.

Apgar score: a means of assessing the health status of the newborn by scoring for color, heart rate, muscle tone, reactivity, and respiration efforts. Scoring is done one and five minutes after birth. Scores range from 0 to 10, and a score of 7 or less at five minutes indicates the need for additional medical care.

Asphyxia: impaired or absent respiratory exchange of oxygen or carbon dioxide. The lungs are unable to oxygenate the body or clear poisonous carbon dioxide.

Aspiration: inhalation of vomitus (or meconium) into the lungs, a potential complication of general anesthesia.

Association: an association exists if two or more variables are found to be statistically dependent. Statistical dependence means that adjustment in one variable will likely be accompanied by changes in other associated variables.

Asynclitism: the fetal head is at an angle, tipped toward one shoulder or with the chin not tucked down on the chest. Asynclitism may interfere with descent of the baby into the maternal pelvis.

Atony: lack of muscle tone, muscle weakness.

Augmentation of labor: stimulation of a labor that began spontaneously in order to increase contraction frequency and strength, usually by IV oxytocin.

Auscultation: listening to body sounds (in obstetrics commonly the fetal heartbeat) with a stethoscope or hand-held ultrasound device.

Bishop score: an evaluation of readiness for labor based on cervical dilation, effacement, consistency, position (the cervix moves from facing posterior toward the sacrum before labor to facing anterior, toward the pubic symphysis, during labor), and station of the presenting fetal part.

Blood patch: a procedure in which a small amount of blood (drawn from the same individual undergoing the procedure) is injected to close holes in the dura mater (covering) of the spinal cord. Holes or leaks in the dura mater are usually the result of a previous lumbar puncture or epidural placement and may cause a post-dural puncture headache.

Bolus (IV): a large amount of (IV) fluid given rapidly, as before an epidural or preoperatively.

Brachial paralysis (brachial plexus injury): injury to a network of nerves serving the arm, shoulder, and chest.

Bradycardia: abnormally slow heart rate. Fetal heart rate <100 beats per minute.

Breech presentation: the baby is head up instead of the normal head down in the pelvis.

  • frank breech: bottom down in pike position, flexed at the hips with legs straight.
  • complete breech: bottom down, flexed at both hips and knees; may convert to an incomplete breech during labor.
  • incomplete breech: usually a footling breech, with one or both feet or knees presenting to the birth canal.

Caput succedaneum: a pressure-caused, fluid-filled swelling under the scalp of the fetal head.

Cardiotocogram: tracing of fetal heart tones and uterine contraction frequency and timing.

Cardiotocography: electronic fetal monitoring combined with measurement of uterine contractions.

Case-control study: see retrospective study.

Case report: reports of a single case or cases of an unusual event.

Cephalic presentation: the fetus presents head down in the maternal pelvis.

  • anterior position: the fetus is head down facing the mother’s back. This position is considered a highly favorable position for dilation and birth. Anterior positions include left occiput anterior (LOA) (most common) or right occiput anterior (ROA).
  • posterior position: the fetus is head down facing the mother’s belly with the back of its head against the maternal sacrum. Posterior positions include left occiput posterior (LOP) or right occiput posterior (ROP).
  • transverse position: the fetus is head downward facing between anterior and posterior, i.e., occiput transverse (OT).

Cephalopelvic disproportion: the fetal head is in a position unfavorable for descent in the maternal pelvis or is too large to fit into the pelvis.

Cerebral palsy: a group of disorders that can involve brain and nervous system functions such as movement, learning, hearing, seeing, and thinking. The exact cause of cerebral palsy remains unknown, but it may result from hypoxia or infection during pregnancy and/or labor.

Chorioamnionitis: infection of the fetal membranes. See also amnionitis.

Clavicular fracture: broken collarbone.

Clinical significance: a variable or intervention is said to be clinically significant if it causes either a measurable improvement or worsening of patient condition. Clinical significance differs from statistical significance because statistical significance cannot provide information about the impact or direction of an intervention.

Clinical trial: researchers take two or more similar groups, submit them to different treatments (or no treatment, i.e., “controls”), and compare outcomes.

Coached pushing: women are instructed to push and hold their breath during second stage of labor for a designated length of time according to the direction of a provider or support person.

Cohort: a group of individuals sharing a common characteristic and observed over time in a study.

Collaborative care: active participation of midwives, obstetricians, and obstetric specialists as informal or formal teams. Collaboration provides mechanisms for communication among caregivers in order to optimize care.

Combined spinal epidural (CSE): a regional analgesia in which a needle is passed into the epidural space, a smaller needle inserted through it is passed through the dural membrane into the intrathecal space (also called the subdural space), and a narcotic or sometimes an anesthetic is injected. The smaller needle is withdrawn, a catheter is passed through the bigger needle and left in the epidural space, and the bigger needle is withdrawn. Conventional epidural analgesia can then be provided when the woman desires additional pain relief.

Confidence interval (confidence limits): the range of possible values for an odds ratio or relative risk within 95% confidence limits, meaning there is only a 5% chance that the true value falls outside the range. If the range does not intersect 1, the ratio is significant.

Composite variable: a variable based on two or more variables (e.g. an Apgar score).

Contraction stress test (CST): a fetal surveillance test that looks at the fetal heart rate response to contractions; contractions may be elicited by nipple stimulation or an oxytocin drip. A “negative” contraction stress test means that no signs of poor oxygenation have been observed in the fetal heart rate.

Confounding (to confound): an element or variable is said to be confounding if it obscures differences between the control and experimental groups in a study so that the results obtained do not reflect the actual relationship between the variables under investigation.

Control (for): to control for a variable is to try to separate its effect from the treatment effect, so it will not confound with the treatment. (See confounding.)

Control group: a group of study participants who receive either no treatment or a placebo. Used in studies comparing outcomes between two identical groups, one of which receives treatment, to investigate what variables may affect or be affected by the intervention or treatment of interest.

Cord prolapse: see umbilical cord prolapse.

Correlation: a measure of association that establishes predictive value for the effect of a set of variables on another. Correlation is tested by a diverse set of statistical measurements.

Crossover: trial participants assigned to one group receive the allocated treatment of the other group.

Crystalloids: nonprotein IV solutes including glucose, salt, or those found in Ringer’s lactate.

Cystocele: a herniation of the posterior bladder through the anterior vaginal wall. A cystocele occurs when the supportive tissue between a woman’s bladder and vaginal wall weakens under excessive stress and stretches, allowing the bladder to bulge into the vagina.

Decelerations: decrease in fetal heart rate. Occurs secondary to decreased placental perfusion, umbilical cord compression, or the vagal response by the fetus as its head descends in the maternal pelvis.

Defensive medicine: occurs when medical providers order tests, procedures, or visits, or avoid high-risk patients or procedures, with the primary goal of reducing their exposure to malpractice liability.

Dehiscence: the opening of a wound, specifically in obstetrics the opening of a uterine cesarean scar; sometimes distinguished from “uterine rupture” by being symptomless. When used in this sense, “dehiscence” is synonymous with “window.”

Delivery, types:

  • assisted: forceps delivery or vacuum extraction.
  • cesarean: surgical delivery.
  • instrumental: usually forceps or vacuum extraction; sometimes also includes cesarean surgery.
  • operative: forceps, vacuum extraction, or cesarean surgery; sometimes the phrase “operative vaginal delivery” excludes cesarean surgery.
  • spontaneous: vaginal birth without instrumental assistance.

Descriptive study: describes characteristics of a sample of individuals. Unlike an experimental study, the investigators do not actively intervene to test a hypothesis, but merely describe the health status or characteristics of a sample from a defined population.

Detrusor muscle: a layer of the urinary bladder wall made of smooth muscle arranged in spiral, longitudinal, and circular bundles. When the bladder is stretched it then signals the nervous system to contract the detrusor muscle. This encourages the bladder to expel urine through the urethra. An overactive detrusor muscle may create a frequent and urgent need to urinate.

Dilation, cervical: the cervix opens.

Disseminated intravascular coagulation (DIC): a pathological activation of coagulation (blood clotting) mechanisms. DIC first causes the formation of small blood clots throughout the vessels of the human body, and then results in severe hemorrhage due to the exhaustion of clotting factors.

Dorsal: of the back.

Dorsal lithotomy: a position typically used during medical procedures on the pelvis or lower abdomen where a patient is placed on their back (dorsum) in a position with legs elevated toward the abdomen and separated in stirrups or footrests (lithotomy).

Double-blind: neither the researcher nor the subject knows whether the subject had the intervention or was in the control group.

Dyspareunia: painful sexual intercourse.

Dystocia: difficult childbirth, often used to mean “slow labor progress.”

Ectopic pregnancy: an abnormal pregnancy in which the fertilized egg implants outside the uterus where it cannot survive. Ectopic pregnancies can cause severe bleeding and possible rupture of the fallopian tubes depending on site of implantation. In cesarean-scar ectopic pregnancy, implantation occurs within the uterine scar.

Edema: an accumulation of an excessive amount of watery fluid in the tissues.

Effacement, cervical: the cervix shortens and becomes soft and thin in preparation for and as part of labor.

Electronic fetal monitoring (EFM): monitoring the fetal heart rate with a machine that either picks up signals through an external ultrasound device or an internal monitor lead attached to the baby’s scalp. Contractions can be monitored by an external pressure sensor or an internal pressure catheter. Data are displayed on a screen and on a paper tracing.

Emesis: vomiting.

Encephalopathy: a disorder or disease of the brain. It can be due to direct injury or illness remote from the brain.

Endometriosis, cesarean scar: de novo endometriosis caused by iatrogenic seeding of endometrial cells into the abdominal wall or uterine wound during surgery, also called cesarean scar endometrioma to indicate that it is a defined mass.

Endometritis: an inflammation or infection of the lining of the uterus (the endometrium).

Epidural space: a space lying outside the first of the two membranes (the dural membrane) that sheathe the spinal cord. When epidural anesthesia is administered, medication is delivered into this space.

Episiotomy: a perineal incision to enlarge the vaginal opening for childbirth.

  • mediolateral: the cut goes down and off to one side.
  • midline (also called median): the cut goes straight down toward the rectum.

Ergot derivatives: synthetic medications derived from ergot fungus that cause vasoconstriction in humans. In obstetrics, ergot derivatives are used to prevent heavy postpartum bleeding or as an emergent intervention for postpartum hemorrhage.

Excess risk: a measure of the association between a specified risk factor and a specified outcome. That is, how much more likely an individual is to get a condition if they are exposed to the risk factor of interest versus if they had never been exposed at all.

Expectant management: watching and waiting.

External cephalic version (ECV): turning a breech baby to vertex by rotating it into a vertex presentation by external manipulation of the woman’s abdomen.

Failure to progress (FTP): absence of progressive cervical change or fetal descent during the active phase of labor. Individual provider or institutional guidelines often establish narrow time periods for labor progress. Cesarean surgery, instrumental vaginal delivery, and augmentation of labor are interventions intended to address a failure to progress.

False-negative rate: the percentage of people diagnosed by a test as healthy who, in fact, have the disease.

False-positive rate: the percentage of people diagnosed by a test as diseased who are, in fact, healthy.

Fetal mortality rate: the number of fetal deaths divided by the sum of live births plus fetal deaths during the same period.

First-degree laceration: see laceration, perineal.

First-stage labor: from the onset of progressive contractions to full dilation of the cervix (10 cm).

Fourth-degree laceration: see laceration, perineal.

Freestanding birth center: a home-like birth setting that is geographically separate from a hospital and may be either autonomous or directly affiliated with a healthcare institution.

Fundal pressure: strong external pressure applied to the top or fundus of the uterus during the second stage of labor in an effort to expedite delivery.

Generalizability: the ability to apply results to individuals and circumstances beyond an original study. A variety of elements are helpful in interpreting generalizability, including study design, sample size, socio-demographic and geographic composition of the study group, and the characteristics of the study setting and clinicians involved in providing care.

Gestational age: the time measured from the first day of the woman’s last menstrual cycle to the current date. Typically expressed in weeks (e.g. 12 weeks gestational age).

Hartmann’s solution: the British version of Ringer’s lactate, an electrolyte replacement IV fluid.

Hazard ratio: an estimate of the ratio between the hazard (chance) of events occurring in the treatment arm of a clinical study and the chance of the same events occurring in the control arm.

Hematocrit (Hct): percentage of blood volume taken up by red blood cells.

Hematoma: a blood-filled swelling.

Hemiparesis: weakness on one side of the body caused by stroke or brain injury.

Hospital: (level of maternity care services)

  • primary care (Level I): a hospital with the capability of caring for the essentially normal mother and infant.
  • secondary care (Level II): a hospital with the capability of caring for mothers and infants with some complications and the ability to stabilize very sick mothers or babies or premature infants for transport to a tertiary care center.
  • tertiary care (Level III): a hospital with the staffing and equipment to handle high-risk expectant mothers and infants.

Hydrophilic dilator (e.g. Laminaria): a substance placed in the cervix that expands when exposed to water, causing mechanical dilation.

Hydrotherapy: the use of water for pain relief, including tub immersion, acupressure or effleurage with a shower jet, and heat to promote relaxation.

Hyperbilirubinemia: elevated level of circulating bilirubin (a waste product of red blood cell breakdown). Hyperbilirubinemia is one of the causes of neonatal jaundice.

Hyperglycemia: high blood sugar.

Hyperstimulus: overstimulation, particularly of uterine contractions.

Hyperstimulation syndrome: excessive uterine activity in conjunction with nonreassuring fetal heart rate.

Hypertension: elevated blood pressure, >140 systolic or >90 diastolic.

Hypertonic: an overly contracted muscle (as in “hypertonic uterus”).

Hypertonus: abnormally high level of muscle tone or contraction. Hypertonicity in the uterus may lead to decreased placental perfusion and fetal distress.

Hyperthermia: abnormally high body heat.

Hypoglycemia: low blood sugar.

Hyponatremia: low blood sodium.

Hypotension: low blood pressure.

Hypotonic solution: a solution with lower salt concentration than in normal cells of the human body.

Hypothermia: abnormally low body heat.

Hypoxia: insufficient oxygen to the body affecting the brain and major organs.

Hypoxic-ischemic encephalopathy (HIE): abnormal neurologic symptoms believed to be caused by the consequent damage of insufficient oxygenated blood reaching the brain.

Iatrogenic: caused by medical treatment or diagnostic procedures. An iatrogenic disorder is a condition that is caused by medical personnel or procedures or that develops through exposure to the environment of a health care facility.

Incontinence, anal: spontaneous leakage of solid or liquid fecal material, often including mucoid discharge or gas.

Incontinence, urinary:

  • stress incontinence: incontinence associated with exercise, laughing, sneezing, or coughing.
  • urge incontinence: sudden need to void followed by involuntary loss.

Independent (Independence): a critical concept in statistics. Two events are said to be independent if one event’s occurrence does not influence the probability that the other event will or will not occur.

Intermittent auscultation: a systematic method of listening to fetal heart tones with an acoustical device or a hand-held doppler at intervals designated by stage of labor and protocol in use. During intermittent auscultation the rate, rhythm, and variability of the fetal heart tones are observed for at least one full minute, typically following a uterine contraction.

Instrumental vaginal delivery: see delivery, types.

Intracervical: within the cervix.

Intrapartum: during labor.

Intrathecal: an adjective that refers to something introduced into or occurring in the space around the spinal cord (subarachnoid space).

Intraventricular hemorrhage: bleeding into the brain’s ventricular system. Depending on severity (grade I-IV), may cause significant brain injury.

Intubation: the placement of a tube into the trachea (windpipe) in order to maintain an open airway in patients who are unconscious or unable to breathe on their own. Oxygen, anesthetics, or other gaseous medications can be delivered through the tube.

Isotonic solution: a solution with concentration of salt identical to the composition of normal human cells.

Ketosis: the body’s metabolic response to starvation or to type I diabetes. In these stressful states the body is unable to mobilize sufficient amounts of glycogen (energy). Fats are metabolized instead, producing ketones, which in large amounts create acidic waste products harmful to the body.

Ketonuria: the presence of excessive amounts of ketones in the urine.

Labor, phases of:

  • latent phase: early labor; labor from the onset of dilation to 3 to 5 cm dilation, after which time the intensity of labor and the rapidity of dilation usually increases.
  • active phase: labor from the point at which the tempo of labor usually increases, generally beginning at 3 to 5 cm dilation.
  • transition phase: the last two or three centimeters of dilation are sometimes distinguished from the rest of the dilation phase of labor by this term.

Laceration, perineal: third- and fourth-degree lacerations are often combined into the single category anal laceration.

  • first degree: a tear into the mucus (top most) layer of vaginal tissue.
  • second degree: a tear into the underlying muscle of the perineum (the equivalent of an episiotomy).
  • third degree: laceration involving the external anal sphincter and/or rectum but not through the sphincter.
  • fourth degree: laceration through the external anal sphincter and/or rectum and into the rectal mucosa.

Lactic acidosis: acidosis (acid pH of the blood) due to lactic acid formation.

Latent phase labor: see labor, phases of.

Likert Scale: a questionnaire format that allows respondents to specify their level of agreement with a list of individual statements (e.g. “Strongly agree,” “Agree,” “Neither agree or disagree,” “Disagree,” “Strongly disagree”).

Lithotomy position: see dorsal lithotomy.

Logistic Regression: used for the prediction of the probability of an event. Logistic regression allows a researcher to predict the likelihood of an outcome of interest from a set of variables that may be continuous, discrete, or dichotomous, or any mix of these. Logistic regression is a helpful statistical test because it provides knowledge of the relationships and strengths among the variables.

Low birth weight (LBW): infant birth weight less than 2500 grams.

Macrosomia: birth weight greater than or equal to 4000 grams (8 lb 12 oz).

Mean: an average value calculated by summing all the observations and dividing by the number of observations.

Mechanical dilator: intracervical insertion of a balloon catheter (e.g. Foley catheter) to promote cervical ripening and dilation.

Meconium: tarry, dark material that accumulates in the fetal bowel during pregnancy. Sometimes the baby passes meconium into the amniotic fluid, a possible sign of fetal distress. If the baby inhales (aspirates) the meconium into its lungs upon taking its first breath, the irritation and the particles may cause a type of pneumonia.

Median: the value that comes half way when the observations are ranked in order.

Medical model: a framework for the provision of healthcare which views processes in the human body in terms of pathophysiology requiring intervention. One example of this framework is the orientation that labor should be a smoothly linear process within a specific timeframe with little individual variation, and that deviation from this pattern requires prompt intervention.

Membrane stripping (or sweeping): separation of the fetal membranes (amniotic sac) from the internal cervical os by digital examination. This separation may cause release of prostaglandins and increase uterine contractions.

Meta-analysis: a study that uses sophisticated statistical techniques to pool data from several studies.

Methodology: the details of how a study was conducted.

Misoprostol: a synthetic Prostaglandin E1 (PGE1, trade name Cytotec) analog that prevents gastric ulcer formation by inhibiting production of gastric acid. One side effect of Misoprostol is its ability to increase uterine tone and contractions. Due to this effect, Misoprostol has been used off-label for pregnancy termination, labor induction, and response to postpartum hemorrhage.

Mode: the most common value in the set. Some datasets can have two (bimodal) or more than two equally common values (multimodal).

Montevideo units: the sum of the intensity of each uterine contraction in a 10 minute period. Accurate calculation can only be done by using an intrauterine pressure catheter (IUPC) for measurement.

Morbidity: injury, disease, or complications following a medical procedure.

Multigravida: a woman who has had more than one pregnancy.

Multipara: a woman who has given birth to more than one child.

Multivariable regression analysis: a statistical analysis that explains or predicts the dependent variable by simultaneously considering all the independent or predictor variables.

Necrotizing enterocolitis: death of intestinal tissue caused by injury (e.g. low perfusion) or overabundance of harmful bacteria.

Neonatal mortality rate (NMR): the number of deaths occurring during the first 28 days after birth (sometimes the first 7 days) divided by the number of live births in the same population over the same time, usually expressed per thousand live births (e.g. 14 per 1,000 live births).

Nitrous oxide (N2O, or “laughing gas”): a colorless nonflammable gas known for its analgesic and anesthetic properties. N2O is administered with oxygen through a face mask or mouthpiece held by a patient.

Non-stress test (NST): a fetal surveillance test that tracks the fetal heart rate during a 20-30 minute period by external fetal monitoring to evaluate it for presence of signs indicating fetal distress.

Non-significant: see statistical significance.

Non-vertex: a fetus presenting any part of its body other than its head (vertex) at the maternal cervix.

Non per os (NPO): Latin, meaning “nothing by mouth.”

Nuchal: having to do with the back of the neck, e.g., a nuchal cord is the umbilical cord wrapped around a fetus’s neck.

Nulligravida: a woman who has never been pregnant.

Nullipara: a woman who has never given birth, sometimes used interchangeably with primipara.

Number needed to harm: a calculated estimate of how many people would need to be treated before one person would experience a harmful outcome or one fewer person would experience a beneficial outcome. It is calculated by dividing the absolute difference into 1. (See also absolute difference.)

Number needed to treat: a calculated estimate of how many people would need to be treated before one person would experience a beneficial outcome. It is calculated by dividing the absolute difference between variables into 1. (See also absolute difference.)

Observational study: a study in which subjects/participants are not divided into control or experimental groups. Investigators track a population of interest and use statistical analysis to examine differences in outcomes.

Occiput anterior: see cephalic presentation.

Occiput posterior: see cephalic presentation.

Odds ratio (OR): the odds of having the condition if the risk factor is present divided by the odds of having condition if the risk factor is absent.

Oligohydramnios: deficient amount of amniotic fluid. Clinically defined as an amniotic fluid index of less than 5 cm.

Operative delivery: see delivery, types.

Order of magnitude: used as comparison between two or more numbers. If two numbers differ by one order of magnitude, one is about ten times larger than the other. If they differ by two orders of magnitude, they differ by a factor of 100.

Oxytocin: a hormone produced by the posterior pituitary in humans that promotes uterine contractions and letdown during lactation. Also known as the “love hormone” because of its release during touch and skin-to-skin contact. Synthetic oxytocin is used for labor induction, augmentation, and active management of the third stage of labor.

Para: short for parity.

Paresthesia: abnormal sensation.

Parity: the condition of having given birth to one or more children.

Parous: having delivered one or more children.

Pelvimetry: measurement of the diameters of the pelvis.

Perinatal mortality rate (PMR): usually defined as the number of fetal deaths occurring after 28 weeks gestation plus the number of neonatal deaths occurring within the first 7 days after birth divided by the number of live born infants of at least 28 weeks; usually expressed per 1000 births.

Perinatalogy: the branch of obstetrics that focuses on the medical and surgical management of high-risk pregnancies. Also known as maternal-fetal medicine.

Perineum: the region of tissue between the bottom of the vagina and the anus.

Peritoneum: the serous membrane that forms the lining of the abdominal cavity and covers most abdominal organs.

Persistent pulmonary hypertension: the failure of the normal transition that occurs after birth that allows circulation in the lungs. The lungs need low pressure in order to circulate blood to remove carbon dioxide (waste) and add oxygen.

Phototherapy: using ultraviolet light to treat neonatal jaundice. Bilirubin, which causes jaundice, is broken down by exposure to light.

Physiologic care: care focused on the promotion and support of labor as a process designed to be successful with minimal intervention. Mobility and upright positioning in labor, skin-to-skin contact for mothers and infants after birth, and physiologic pushing are examples of physiologic maternity care.

Placebo effect: from the Latin “I shall please,” the improvement seen after taking an inert substance.

Placenta accreta: abnormal attachment of the placenta into the muscular wall of the uterus. This condition causes severe hemorrhage.

Placenta increta: deep attachment of the placenta into uterine muscle.

Placenta percreta: growth of placenta completely through the uterine wall.

Placenta previa: the placenta implants low, partially or completely overlaying the cervix. This condition may lead to hemorrhage as the cervix begins to dilate.

Placental abruption: separation of the placenta from the wall of the uterus before birth of the infant. This separation may be partial or complete. Separation of the placenta may cause both maternal and fetal hemorrhage.

Pneumonitis: inflammation of lung tissue due to mechanical (e.g., meconium aspiration) or infectious cause.

Pneumothorax (collapsed lung): the collection of air in the space around the lungs so that it cannot expand as normal.

Polycythemia: an overabundance of red blood cells in the body’s circulatory system. Clinically defined as a hematocrit greater than 65%.

Pooled: data from several sources/studies combined for analysis.

Population-based study: an investigation using a broad sample of individuals from a community or defined group. This type of study is often used to examine the prevalence of a condition or event of interest in the population under study.

Positive pressure ventilation (PPV): refers to the process of forcing air into the lungs of a patient who is not breathing or exhibiting a very low respiratory rate using a specialized bag and mask in order to increase oxygenation.

Post-dural puncture headache: a complication of puncture of the dura mater (lining that surrounds the brain and spinal cord). Typically occurs hours to days after puncture and presents with symptoms such as headache and nausea that typically worsen when the patient assumes an upright posture. Treated by administration of a blood patch.

Posttraumatic stress disorder (PTSD): an anxiety disorder that can develop after exposure to a terrifying event or ordeal in which grave physical harm occurred or was threatened. Individuals diagnosed with PTSD may experience flashbacks to the traumatic event and avoid events or environments that remind them of the original event.

Postdates: see postterm

Postterm: describes pregnancy or birth after 42 completed weeks gestation.

Posterior position: see cephalic presentation.

Postpartum: after birth.

Power: the ability to detect a true difference in the sample data. The power of a study depends on the size of the study population and the frequency of the outcome of interest.

Precipitous birth (or labor): total labor duration less than three hours.

Predictive value: the percentage of subjects who will correctly be identified as having (positive predictive value) or not having (negative predictive value) a disease, given its prevalence among that particular population.

Preeclampsia: a pregnancy complication characterized by excess protein in the urine (>2+), and new-onset hypertension after 20 weeks of gestation.

Prelabor rupture of membranes (PROM): spontaneous rupture of the fetal membranes before the onset of labor.

Presentation: the part of the baby presenting at the birth canal. This is almost always the head but may be the buttocks, feet, face, brow, or shoulder. See also cephalic presentation; breech presentation.

Preterm: birth prior to 37 weeks gestation.

Primary cesarean: a first cesarean, as opposed to a repeat cesarean.

Primary cesarean rate: the total number of cesareans divided by the total number of women giving birth who had not previously had a cesarean.

Primary care center (Level I hospital): see hospital.

Primigravida: a woman having her first pregnancy.

Primipara: a woman who has given birth for the first time, often used interchangeably with nullipara.

Prospective study: a study that assembles a population with certain common characteristics and follows them forward in time to see if they are more likely to have some particular outcome compared with controls who are similar in other respects but who do not share the target characteristics.

Prostaglandin E2 (PGE2): a naturally occurring hormone. PGE2 plays an important role in the complex set of biochemical and structural alterations involved in cervical ripening.

Provider effect: how the philosophy or methodology guiding a healthcare provider’s practice influences outcomes for the population receiving care.

Pruritis: itching.

P-value: the probability that the observed difference is due to chance. Usually values below 0.05, or 5%, are considered significant, meaning that the results are unlikely to be due to chance.

Pyrexia: elevated body temperature, fever.

Qualitative research: investigates experiences or the reasons behind behavior (e.g. a study of women’s thoughts and feelings about receiving a breast cancer diagnosis, or a study of families’ motivations to co-sleep).

Quantitative research: systematic investigation of the relationship between phenomena, which must be measurable and specific. Measurement and statistical analysis are essential processes of quantitative research.

Randomized controlled trial (RCT): a clinical trial in which subjects are randomly allocated to study group(s) or control group.

Recall bias: the propensity of memory to play tricks.

Rectocele: herniation of the anterior rectal wall through the posterior vaginal wall.

Recumbent: lying down.

Regression analysis: any technique for analyzing a group of variables, where the focus is on the relationship between the dependent variable and one or more independent variables. This process helps researchers understand how the value of the dependent variable changes when any one of the independent variables is adjusted.

Relative difference: the ratio of the absolute difference between two variables and a baseline value such as the maximum of the two variables. For example: If variable A is 300 and variable B is 400, the absolute difference is 400-300 = 100, while the relative difference is |400-300|/400 = 0.25.

Relative risk (RR): the probability of developing the outcome if the risk factor is present divided by the probability of developing the problem if it is absent.

Respiratory distress syndrome (RDS): is most common in premature infants born before 32 weeks. It is caused by a deficiency in surfactant that keeps the alveoli in the lungs open during respiration.

Retrospective study: a study that collects a population with a particular outcome or problem and then delves into the past for characteristics or events they have in common that are not shared by members of a control group not having that outcome or problem.

Ringer’s lactate: an electrolyte replacement IV fluid.

Ripening, cervical: through either natural processes or artificial induction (see hydrophillic dilator, mechanical dilator, membrane stripping, misoprostol, and prostaglandin E2) the cervix becomes soft, effaced, and begins to dilate.

Rupture: in obstetrics, the opening of the uterine scar; sometimes used to mean all varieties, including symptomless windows, but now usually defined as scar openings penetrating all layers of the uterus and sometimes further limited to complete rupture accompanied by symptoms (such as bleeding or nonreassuring fetal heart rate) that pose a risk to mother or baby.

Secondary care center (Level II hospital): see hospital.

Second-degree laceration: see laceration, perineal.

Second stage: the stage of labor that begins with full cervical dilation and ends with the birth of the baby.

Sensitivity (of a test): the percentage of the population tested that will be accurately identified as affected by a disease or condition.

Sepsis: a clinical condition in which infectious agents or products of infection (bacterial toxins) enter the blood and profoundly affect functions like blood pressure and body temperature.

Shoulder dystocia: the head of an infant is born, but the shoulders are hung up behind the pubis. Shoulder dystocia is considered an obstetric emergency because of the risk of hypoxia to the infant.

Significant difference: the observed difference is considered to be a true difference, not the result of chance. The usual cutoff probability value (p value) is p < 0.05 or a confidence interval that does not intersect 1.

Small for gestation age (SGA): birth weight and/or length less than 10th percentile for gestational age.

Specificity (of a test): the percentage of the population that will be correctly diagnosed as not affected by a disease or condition.

Spontaneous delivery: see delivery, types.

Stages of labor: see first stage; second stage; third stage.

Standard deviation (SD): a measure of variability or dispersion within a data set. Assuming normal distribution (a bell-shaped or Gaussian curve), about 95% of all values will be found within two standard deviations on either side of the mean.

Station: the location of the presenting fetal part with respect to the ischial spines of the mother’s pelvis. Location of the fetal part at the spines is 0 station. Minus station is centimeters above the spines (as in -1, -2), and plus station is centimeters below the spines (as in +1, +2).

Statistical power: see power.

Statistical significance: indicates that a result is unlikely to have occurred by chance. Statistical significance cannot provide information about effect size or clinical significance. Tools for determining statistical significance may include calculation of effect size and p-value.

Stillbirth: delivery of non-living fetus after 20 weeks of gestational age.

Stress urinary incontinence: see incontinence, urinary.

Subarachnoid space: the space below both of the membranes covering the spinal cord.

Subgroup analysis: an analysis in which a study intervention is evaluated in a defined subset of the study’s participants (e.g. women 25-30 versus all women enrolled).

Supine: lying on the back.

Supine hypotension: when a pregnant woman lies supine, the weight of the uterus and baby compresses the large blood vessels serving her lower body and the uterus. This can cause decreased perfusion to the uterus and fetal distress.

Surrogate outcome (or surrogate endpoint): a laboratory measurement or a physical sign used as a substitute for a direct measurement of how a patient feels, functions, or survives. Surrogate outcomes are often poor predictors of clinically important outcomes.

Survival curve: a statistical representation in the form of a graph showing the percentage of individuals in study groups (e.g. intervention versus no intervention) developing an outcome of interest over time (e.g. breastfeeding cessation).

Systematic review: a literature review focused on a research question that tries to identify, appraise, select, and synthesize all high quality research evidence relevant to that question.

Tachycardia: abnormally fast heart rate. Defined as a fetal heart rate greater than 160 beats per minute.

Tachypnea: abnormally rapid breathing. Clinically defined as an infant respiratory rate greater than 65 breaths per minute.

Tachysystole: abnormally frequent contractions.

Term: a full-length pregnancy, usually defined as between 37 and 42 completed weeks gestation. Earlier than 37 weeks is considered preterm, and later than 42 weeks has been considered postdates or postterm, but increasingly this threshold is being set at less than 42 weeks. Premature and post-mature are sometimes incorrectly used as synonymous with preterm and post-term.

Tertiary care center (Level III hospital): see hospital.

Tectonic contractions: abnormally long contractions.

Third-degree laceration: see laceration, perineal.

Third stage: the stage of labor that begins with the birth of the baby and ends with the birth of the placenta.

Thromboembolism: a clot that has formed in a blood vessel, which may result from injury, inflammation, decreased mobility, hormonal influences, or a combination of these factors. In extreme cases clots may move through the circulatory system until they become lodged, causing decreased perfusion and injury, which may become life-threatening.

Tocodynamometry: measurement of the force of uterine contractions.

Tocolytic: a uterine relaxant drug, given in response to hypertonic contractions or fetal distress.

Transient tachypnea of the newborn: rapid breathing in a newborn to compensate for poor oxygenation of the lungs caused by excess fluid in the lungs or by delayed or impaired clearance of amniotic fluid. Typically resolves with supportive care.

Transition: see labor, phases of.

Trial of labor (TOL): most commonly used in reference to planned vaginal birth after cesarean.

Type I error: the statistical error of finding a significant difference when no true difference exists.

Type II error: the statistical error of not finding a significant difference when a true difference exists.

Umbilical cord blood (cord blood): blood that remains in the placenta and in the attached umbilical cord after childbirth. Cord blood is often collected and banked because it contains stem cells. A provider may also collect cord blood for pH analysis if an infant had a low Apgar score. An acidic cord blood pH may indicate an infant was under stress and had low oxygen reserve at the time of birth.

Umbilical cord prolapse: descent of umbilical cord past the presenting part, which can impair blood flow to the fetus. This obstetrical emergency is more common when the baby is not head down or membranes rupture (or are artificially ruptured) before the head is well applied to the cervix.

Unadjusted: results based on data without controlling for influential variables.

Unattended childbirth (unassisted childbirth, or freebirth): home birth without assistance from a qualified provider.

Urinary incontinence: see incontinence, urinary.

Uterine dehiscence: see dehiscence.

Uterine inversion: usually occurs with cord traction during active management of third stage; the topmost part of the uterus is pulled either partially or completely through the cervix, turning the uterus inside out. This is an obstetric emergency that can result in severe hemorrhage.

Uterine rupture: see rupture.

Vertex presentation: baby presents head down.

Wound dehiscence: a surgical complication in which a wound breaks open along a surgical suture.