8 Obstetrics

Learning Objectives

  • Identify the common processes in obstetrics
  • Describe the specialty of obstetrics
  • Spell the medical terms used in obstetrics and use correct abbreviations
  • Identify the medical specialties associated with obstetrics
  • Explore common complications and procedures related to obstetrics

Obstetric Word Parts

Click on prefixes, combining forms, and suffixes to reveal a list of word parts to memorize related to obstetrics.

Introduction to Obstetrics

Obstetrics is a specialty that is concerned with the mother and fetus during pregnancy, childbirth and the immediate postpartum period. Obstetricians study obstetrics and gynecology and are referred to as OB/GYN Obstetrics and Gynecology.

Watch this video:

Obstetrics Medical Terms


Fertilization occurs when a sperm and an oocyte (egg) combine. Because each of these reproductive cells is a haploid cell containing half of the genetic material needed to form a human being, their combination forms a diploid cell. This new single cell is called a zygote.

Most of the time, a woman releases a single egg during an ovulation cycle.

  • In approximately 1 percent of ovulation cycles, two eggs are released and both are fertilized.
    • Two zygotes form, implant, and develop, resulting in the birth of dizygotic (or fraternal) twins. Because dizygotic twins develop from two eggs fertilized by two sperm, they are no more identical than siblings born at different times.
  • Less common, one zygote can divide into two separate offspring during early development. This results in the birth of monozygotic (or identical) twins.

A full-term pregnancy lasts approximately 270 days (approximately 38.5 weeks) from conception to birth. Because it is easier to remember the first day of the last menstrual period (LMP) than to estimate the date of conception, obstetricians set the due date as 284 days (approximately 40.5 weeks) from the LMP. This assumes that conception occurred on day 14 of the woman’s cycle, which is usually a good approximation. The 40 weeks of an average pregnancy are usually discussed in terms of three trimesters, each approximately 13 weeks. During the second and third trimesters, the pre-pregnancy uterus is about the size of a fist and grows dramatically to contain the fetus, causing a number of anatomical changes in the mother.

Stages of Childbirth

The process of childbirth can be divided into three stages (see Figure 8.1):

  • cervical dilation
  • expulsion of the newborn
  • after birth

For vaginal birth to occur, the cervix must dilate fully to 10 cm in diameter, wide enough to deliver the newborn’s head. The dilation stage is the longest stage of labor and typically takes 6-12 hours. However, it varies widely and may take minutes, hours, or days, depending in part on whether the mother has given birth before. In each subsequent labor, this stage tends to be shorter.

This multi-part figure shows the different stages of childbirth. The top panel shows dilation of the cervix (undilated vs fully dilated), the middle panel shows birth (presentation of the head, rotation and delivery of anterior shoulder, delivery of posterior shoulder, delivery of lower body and umbilical cord), and the bottom panel shows afterbirth delivery.
Figure 8.1 Stages of Childbirth. The stages of childbirth include Stage 1, early cervical dilation; Stage 2, full dilation and expulsion of the newborn; and Stage 3, delivery of the placenta and associated fetal membranes. (The position of the newborn’s shoulder is described relative to the mother). From Betts, et al., 2021. Licensed under CC BY 4.0.

Concept Check

  • How is a due date determined?
  • Explain the difference between a monozygotic pregnancy and a dizygotic pregnancy.

Homeostasis in the Newborn: Apgar Score

In the minutes following birth, a newborn must undergo dramatic systemic changes to be able to survive outside the womb. An obstetrician, midwife, or nurse can estimate how well a newborn is doing by obtaining an Apgar score (Fig 8.2). The Apgar score was introduced in 1952 by the anesthesiologist Dr. Virginia Apgar as a method to assess the effects on the newborn of anesthesia given to the laboring mother. Healthcare providers now use it to assess the general well-being of the newborn, whether or not analgesics or anesthetics were used.

The technique for determining an Apgar score is quick and easy, painless for the newborn, and does not require any instruments except for a stethoscope. A convenient way to remember the five scoring criteria is to apply the mnemonic APGAR:

  • Appearance (skin color)
  • Pulse (heart rate)
  • Grimace (reflex)
  • Activity (muscle tone)
  • Respiration 
Fig 8.2 The five Apgar criteria, skin color, heart rate, reflex, muscle tone, and respiration, are assessed and each criterion is assigned a score of 0, 1, or 2. Scores are taken at 1 minute after birth and again at 5 minutes after birth. Each time scores are taken, the five scores are added together. High scores (out of a possible 10) indicate the baby has made the transition from the womb well, whereas lower scores indicate that the baby may be in distress.

Of the five Apgar criteria, heart rate and respiration are the most critical. Poor scores for either of these measurements may indicate the need for immediate medical attention to resuscitate or stabilize the newborn. In general, any score lower than 7 at the 5-minute mark indicates that medical assistance may be needed. A total score below 5 indicates an emergency situation. Normally, a newborn will get an intermediate score of 1 for some of the Apgar criteria and will progress to a 2 by the 5-minute assessment. Scores of 8 or above are normal.

Obstetrics Medical Terms not Easily Broken into Word Parts

Obstetrics Abbreviations

Medical Terms in Context

Procedures Related to Obstetrics

In Vitro Fertilization (IVF)

IVF, which stands for in vitro fertilization, is an assisted reproductive technology. In vitro, which in Latin translates to in glass, refers to a procedure that takes place outside of the body. There are many different indications for IVF. For example, a woman may produce normal eggs, but the eggs cannot reach the uterus because the uterine tubes are blocked or otherwise compromised. A man may have a low sperm count, low sperm motility, sperm with an unusually high percentage of morphological abnormalities, or sperm that are incapable of penetrating the zona pellucida of an egg. Figure 8.3 illustrates the steps involved in IVF.

This multi-part figure shows the different steps in in vitro fertilization. The top panel shows how the oocytes and the sperm are collected and prepared (text reads: 1) Ovarian hyperstimulation, 2) Transvaginal oocyte retrieval, 3)Sperm preparation, 4) Sperm and the egg are incubated, 5) Embryo culture, 6) Embryo transfer, then the last panel shows either pregnancy or the process is repeated.
Figure 8.3 In Vitro. The ASRM Publications describes In vitro fertilization (IVF) as a method of assisted reproduction that involves combining an egg with sperm in a laboratory dish. If the egg fertilizes and begins cell division, the resulting embryo is transferred into the woman’s uterus where it will hopefully implant in the uterine lining and further develop. After the various screening tests are conducted, and the woman has started the stimulation phase, here is a rundown of the next crucial steps. This shows how IVF (in vitro fertilization) generally works. Copyright ESCO Medical

Test Yourself


[CrashCourse]. (2019, November 23). Reproductive System, Part 4 – Pregnancy & Development: Crash Course A&P #43 [Video]. YouTube. https://youtu.be/BtsSbZ85yiQ


Unless otherwise indicated, this chapter contains material adapted from Anatomy and Physiology (on OpenStax), by Betts, et al. and is used under a a CC BY 4.0 international license. Download and access this book for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction.



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Medical Terminology Copyright © 2022 by Stacey Grimm; Coleen Allee; Elaine Strachota; Laurie Zielinski; Traci Gotz; Micheal Randolph; and Heidi Belitz is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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