Obstetrics

Anatomy or system affected: Reproductive system, uterus

Definition: The medical science dealing with pregnancy and childbirth, including the health of both mother and unborn infant and the delivery of the child and the placenta at the time of birth

Science and Profession

Obstetrics is the branch of medical science dealing with pregnancy and childbirth in women. Once conception has occurred and a woman is pregnant, major physiological changes occur within her body as well as within the body of the developing embryo or fetus. Obstetrics deals with these changes leading up to and including childbirth. As such, obstetrics is a critical branch of medicine, for it involves the complex physiological events by which every person comes into existence.

The professional obstetrician is a licensed medical doctor whose area of expertise is pregnancy and childbirth. Often, the obstetrician is also a specialist in the closely related science of gynecology, the study of diseases and conditions that specifically affect women, particularly nonpregnant women. The obstetrician is especially knowledgeable in female anatomy and physiology, including the major bodily changes that occur during and following pregnancies. Obstetricians also have a detailed understanding of the necessary diagnostic procedures for monitoring fetal and maternal health, and they are educated in the latest technologies for facilitating a successful pregnancy and childbirth with minimal complications. Obstetrical care is also provided by certified nurse midwives (CNMs) and by nurse practitioners, particularly those with certification in women’s health (women’s health care nurse practitioners).

Broadly, the diseases and conditions managed by the clinicians in this field include preconception counseling, normal prenatal care, and the management of pregnancy-specific problems, such as preeclampsia, premature labor, gestational diabetes, premature rupture of membranes, multiple gestations, fetal growth problems, and Rh incompatibility and isoimmunization. In addition, obstetricians manage medical problems that can occur in any woman, but that take on special importance in pregnancy, such as thyroid disorders or infections. Obstetricians make assessments and decisions regarding when a baby is best delivered, particularly if there are in-utero conditions that make it safer for the baby to be born immediately, even if prematurely. Obstetricians manage both normal and high-risk labors. They are able to assess the progress and position of the infant as it makes its way down the birth canal. They are knowledgeable about pain control options during labor and make decisions regarding when a cesarean section is indicated. Obstetricians assist with normal vaginal deliveries, either spontaneous or induced and sometimes use special instruments, such as forceps or vacuum-suction devices. They also perform cesarean sections. Obstetricians are trained in appropriate postpartum care for the mother and infant.

In natural, spontaneous fertilization, pregnancy begins at conception, with the fertilization of a woman’s egg by a man’s sperm following sexual intercourse, the chances of which are highest if intercourse takes place during a two-day period following ovulation. Ovulation is the release of an unfertilized egg from the woman’s ovarian follicle, which occurs roughly halfway between successive periods during her menstrual cycle. Fertilization usually occurs in the upper one-third of one of the woman’s fallopian tubes connecting the ovary to the uterus. Upon entering the woman’s vagina, sperm must travel through her cervix to the uterus and up the fallopian tubes, only one of which contains a released egg following ovulation.

Once fertilization has occurred, the first cell of the new individual, called a zygote, is slowly pushed by cilia down the fallopian tube and into the uterus. Along the way, the zygote undergoes several mitotic cellular divisions to begin the newly formed embryo, which at this point is a bundle of undifferentiated cells. Upon reaching the uterus, the embryo implants in the lining of the uterus. Hormonal changes occur in the woman’s body to maintain the pregnancy. One of these hormones is human chorionic gonadotropin, which is the chemical detected by most pregnancy tests. Failure of the embryo to be implanted in the endometrium and subsequent lack of hormone production (specifically the hormone progesterone) will cause release of the endometrium as a bloody discharge; the woman will menstruate, and there will be no pregnancy. Therefore, menstrual cycles do not occur during a pregnancy.

The embryo will grow and develop over the next forty weeks of gestation. The heart forms and begins beating at roughly five and one-half weeks following conception. Over the next several weeks and months, major organ systems begin to organize and develop. By the end of the first three months of the pregnancy, the developing human is considered a fetus. All the major organ systems have formed, although not all systems can function yet. The fetus is surrounded by a watery amniotic fluid within an amniotic sac. The fetus receives oxygen and nutrients from the mother and excretes waste products into the maternal circulation through the placenta. The fetus is connected to the placenta via the umbilical cord. During the second and third trimesters, full organ system development; massive cell divisions of certain tissues, such as nervous, circulatory, and skeletal tissue; and preparation of the fetus for survival as an independent organism occur.

Changes also occur in the mother. Increased levels of the female steroid hormone estrogen create increased skin vascularization (that is, more blood vessels near the skin) and the deposition of fat throughout her body, especially in the breasts and the buttocks. The growing fetus and stretching uterus press on surrounding abdominal muscles, often creating abdominal and back discomfort and potentially leading to acid reflux. Reasonable exercise is important for the mother to stay healthy and to deliver the baby with relative ease. A balanced diet also is important for the nourishment of her body and that of the fetus. A diet rich in folic acid is particularly important.

Late in the pregnancy, the protein hormones prolactin and oxytocin will be produced by the woman’s pituitary gland. Prolactin activates milk production in the breasts. Oxytocin causes muscular contractions, particularly in the breasts and in the uterus during labor. Near the time of birth, drastically elevated levels of the hormones estrogen and oxytocin will cause progressively stronger contractions (labor pains) until the baby is forced through the vagina and out of the woman’s body to begin its independent physical existence. The placenta, or afterbirth, is discharged shortly thereafter.

Diagnostic and Treatment Techniques

The role of the obstetrician is to monitor the health of the mother and unborn fetus during the course of the pregnancy and to deliver the baby successfully at the time of birth. Once the fact of the pregnancy is established, the obstetrician is trained to identify specific developmental changes in the fetus over time to ensure that the pregnancy is proceeding smoothly.

The mainstay of diagnosis is the physical examination during prenatal visits. Early in the pregnancy, prenatal visits typically occur once monthly, but they become more frequent as the pregnancy progresses. During these visits, the woman may receive counseling regarding a balanced diet, folic acid and iron supplementation, and substances, foods, or activities to avoid that may pose a risk to the pregnancy. The woman’s growing uterus is measured to confirm proper growth, and if indicated, a vaginal or cervical examination may be performed. After ten weeks of gestational age, fetal heart tones are also assessed at every prenatal visit using a simplified ultrasonic technique to ensure that they are within the normal number of beats per minute. Fetal heart tones that are abnormally slow may indicate a fetus in jeopardy.

The other main component of diagnosis is through laboratory tests. Early in the pregnancy, the woman will receive a Pap test to screen for cervical cancer. Blood tests will be ordered to determine whether the mother is a carrier of the human immunodeficiency virus (HIV), hepatitis B virus (HBV), or hepatitis C virus, which can be transmitted to the fetus. In addition, the mother is checked for anemia, and the blood type of the mother is assessed. If the mother’s blood type indicates that she is Rh-negative, she will receive RhoGAM in the third trimester to prevent the development of a disease called isoimmunization, a condition that could be fatal to the fetus. An additional diagnostic test performed routinely during pregnancy is a screening test for gestational diabetes, which many pregnant women are at risk for developing.

Another important method of diagnosis in obstetrics is ultrasonography. Ultrasonography early in pregnancy can determine the gestational age of a pregnancy in cases in which a woman’s last menstrual period is unverified. The correct development of the fetus and the presence of any birth defects can be assessed using this procedure. Ultrasound can also determine whether the placenta is growing in a safe location and whether the proper amount of amniotic fluid is found in the amniotic sac. Ultrasound is also a useful tool in guiding diagnostic procedures. For instance, amniocentesis can be safe when performed under ultrasound guidance. Finally, one of the main methods of diagnosis in the third trimester is fetal heart monitoring. This technique involves following the heartbeat of the infant while in utero. Any concerning dips in the heart rate may be indicative of a poor fetal state and a cause for increased monitoring or, in extreme cases, delivery of the infant.

Obstetricians have at their disposal a variety of treatment modalities. They are trained to manually turn fetuses that are in a breech (feet-first) position, a procedure called external cephalic version. In cases where the artificial induction of labor is necessary, the obstetrician may employ mechanical or hormonal means of cervical dilation, followed by infusions of a drug called Pitocin to stimulate contractions or the artificial rupture of the amniotic sac to promote natural contractions. When immediate delivery of the infant is needed, and the chances of it emerging via the vaginal route are remote, then the obstetrician may perform a cesarean section. Common indications for cesarean section include fetal distress, breech position, multiple gestation, preeclampsia, and lack of progress in labor.

Other treatments commonly used by obstetricians include the use of medications, such as magnesium, to relax the uterus in cases of premature labor and maternal steroid injections to induce fetal lung maturity when the fetus is premature but delivery is anticipated. When a woman experiences difficulty in the final stages of labor, and the fetal head has descended almost to the vaginal opening, the obstetrician may employ forceps or vacuum devices to facilitate the delivery, particularly in cases of fetal distress. Obstetricians also treat the complications associated with childbirth, including postsurgical care after a cesarean section and repair of any lacerations of the vagina, cervix, or rectum after vaginal delivery.

Perspective and Prospects

Obstetrics is central to medicine because it deals with the very process by which all humans come to exist. The health of the fetus and its mother in pregnancy is of primary concern to these doctors. The field of obstetrics has blossomed as a sophisticated specialty, more likely to be practiced by obstetricians, certified nurse midwives, and specially trained and certified nurse practitioners rather than the general practitioners who used to provide this care.

Advances in medical technology have enabled more precise analysis and monitoring of the fetus inside the mother’s uterus, and obstetrics has therefore become a complex specialty in its own right. Technology, such as ultrasonography and fetal heart rate monitoring, among other techniques, allows the obstetrician to collect a much larger supply of fetal data than was available to the general practitioner prior to the 1960s. Increased data availability enables the obstetrician to monitor the pregnancy closely and to identify any problems earlier.

Advances in product development continue to improve the diagnostic ability of obstetricians. One example is the development of a test for fetal fibronectin, which enables obstetricians to predict which patients are at low risk of premature delivery. This test involves a simple swab of the upper vagina. When negative, this test is highly reliable and allows the pregnant patient to leave the hospital and avoid prolonged and unnecessary hospitalization.

Advances in prenatal diagnosis and basic science have made it possible for parents to obtain information about their fetuses down to the molecular level. Through techniques, such as amniocentesis and chorionic villus sampling (in which a small sample of placental cells is obtained early in pregnancy), genetic analysis has enabled the detection of chromosomal defects responsible for defects responsible for inherited diseases (such as cystic fibrosis). Amniocentesis has also made it possible to detect biochemical changes that may be indicative of major structural defects in the fetus, as well as to assess the developmental maturity of organs, such as the lungs.

Advances in medical practice have dramatically decreased the morbidity and mortality of premature birth. For instance, with the introduction and widespread use of maternal steroid injections, the severity of serious diseases of prematurity, such as respiratory distress syndrome, has been dramatically reduced. The development of drugs against HIV has prevented the transmission of the virus from mother to infant in many cases.

The medical science of obstetrics continues to advance. There is ongoing research into the physiology and basic science of preeclampsia and eclampsia, potentially dangerous diseases peculiar to pregnancy. Fetal surgery programs at academic centers open the possibility that serious birth defects may be correctable while the fetus is in utero. Although many controversies exist in the field of obstetrics, an increased push toward medical practice grounded in scientific evidence promises many exciting advances in the future. It is hoped that many of these advances will result in improved outcomes and quality of life for patients.

Bibliography

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Cunningham, F., et al. Williams Obstetrics. 26th ed., McGraw, 2022.

Gabbe, Steven G., Jennifer R. Niebyl, and Joe Leigh Simpson, eds. Obstetrics: Normal and Problem Pregnancies. 7th ed., Saunders, 2017.

Gaudin, Anthony J., and Kenneth C. Jones. Human Anatomy and Physiology. Harcourt, 1997.

Harkness, Gail, ed. Medical-Surgical Nursing: Total Patient Care. 10th ed., Mosby, 1999.

Limmer, Daniel, et al. Emergency Care. 12th ed., Brady, 2012.

Mandal, Ananya. "What is Obstetrics?" News Medical, 22 Jan. 2023, www.news-medical.net/health/What-is-Obstetrics.aspx. Accessed 30 July 2023.