What are obstetrics?

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, gestational
diabetes, premature labor, 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 to be 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 in order 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 turn manually 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.

New 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
currently 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.

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