18
Learning Objectives
- Identify the processes involved in human reproduction and childbirth
- Evaluate the specialty of obstetrics
- Differentiate the medical terms used in obstetrics and use correct abbreviations
- Recognize the medical specialties associated with obstetrics
- Discover common complications and procedures related to obstetrics
Obstetrics 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:
Media 18.1. Reproductive System, Part 4 – Pregnancy & Development: Crash Course A&P #43 [Online video]. Copyright 2015 by CrashCourse.
Practice Medical Terms Related to Obstetrics
Fertilization
Fertilization occurs when sperm and an oocyte 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% pof 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 18.1):
- 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 to 12 hours. However, it varies widely and may take minutes, hours, or days, depending in part on whether the mother has given bir