Maternal Development
A woman’s physical state begins to change from
as early as the implantation of the fertilized egg and
continues to change throughout gestation. The ability
of a woman to alter herself to support and nurture the
development of another being within her own body
is one of nature’s most impressive feats. From a physi-
ologic standpoint, the maternal body remodels al-
most all of its organ systems, from heart to hormones,
to prepare for the upcoming nine-month gestation.
These changes result in the various signs and symp-
toms characteristic of pregnancy.
In general, a typical gestation, or pregnancy, lasts
nine months or three trimesters of three months. Tri-
mesters are used to mark significant milestones in a
pregnancy. For example, most spontaneous miscar-
riages occur prior to the end of the first trimester.
The end of the second trimester usually is a good time
to recheck maternal lab values, such as the blood
count, and to screen for diabetes in pregnancy. From
an obstetrician’s standpoint, a gestation is measured
in weeks. Because different women have different ten-
dencies toward ovulation (some ovulate earlier in
their menstrual cycles, some later), it is difficult to es-
tablish a gestational age from the time of fertilization.
Instead doctors and midwives calculate the gestation-
al age from a more reliable indicator: the first day of
the woman’s last normal menstrual period. This start-
ing time is usually about two weeks prior to ovulation.
The due date can be quickly calculated using a simple
formula: adding seven days to the date of the start of
the last normal menstrual period, then subtracting
three months. The resulting month and day repre-
sent the expected delivery date of a full-term gesta-
tion.
One of the most obvious signals of pregnancy is
the interruption of a woman’s menstrual cycle. This
sign is most reliable in women who have regular, con-
sistent menses (menstrual flows). A period that is ten
days late or more in a woman with regular menses can
be considered a strong indicator of pregnancy. This
suspicion is strengthened if a woman goes on to skip
her next period altogether. This qualification
changes for women who have a history of skipping pe-
riods or have erratic cycles that are affected by envi-
ronmental or physical stressors. For these women, a
pregnancy test is the best way to ascertain pregnancy.
What is the most reliable way to determine wheth-
er a woman is pregnant? There are dozens of home
pregnancy tests available. These are good initial mea-
sures to use. Although some companies state that
their tests are greater than 97 percent accurate, some
individuals fail to use these tests properly, which can
result in a lower than expected accuracy rate. Studies
done in the early 1980s and 1990s showed that the ac-
curacy rates of home pregnancy tests ranged from 70
percent to 83 percent for women who were actually
pregnant. The best way to obtain a diagnosis is to un-
dergo a blood test ordered by a doctor and performed
by trained technicians. These tests use chemical anal-
ysis to measure the presence of a hormone called
human chorionic gonadotropin (HCG). HCG is pro-
duced by placental cells and is expressed in maternal
blood and urine almost immediately from the day the
embryo implants in the uterus. These biochemical
tests determine the level of hormone in a woman’s
blood sample. Increasing levels of HCG, along with
the other symptoms and signs of pregnancy, provide
the most reliable, consistent, and reproducible results
for determining pregnancy.
Other symptoms of pregnancy that are common-
ly seen include nausea, fatigue, changes in urinary
habits, and ultimately the perception of fetal move-
ment. Episodes of nausea and occasional vomiting,
also known as ‘‘morning sickness,’’ occur around six
weeks from the start of a woman’s last menstrual peri-
od. Typically, the woman experiences a few episodes
of nausea and vomiting, most commonly for a few
hours during the morning. These episodes usually
pass by the end of the first trimester. Occasionally,
women will have more serious episodes of vomiting
marked by increased frequency and intolerance of
any food or liquid intake. This condition, known as
hyperemesis gravidarum, can persist throughout
pregnancy. Treatment entails the use of antinausea
medications, and if cases are severe enough, hospital-
ization for intravenous rehydration.
Changes in urinary habits are noted during the
first trimester. At that time, the growing uterus begins
to exert more force on the bladder, producing the
sensation of fullness and increasing the number of
trips to the bathroom. As pregnancy continues, the
uterus expands out of the pelvis, relieving some pres-
sure on the bladder and decreasing urinary frequen-
cy. As the time of labor approaches, however, the
fetus ‘‘drops’’ into the pelvis and reexerts pressure on
the bladder, resulting in a return of frequent urina-
tion.
The first sensation of fetal movement, also known
as the ‘‘quickening,’’ is reported by most women to
occur between sixteen and twenty weeks. These move-
ments are described as ‘‘fluttering’’ or ‘‘tickles’’ in the
abdomen. First-time mothers usually report that the
quickening occurs later than women who have previ-
ously gone through pregnancy. Although this event
is not fully diagnostic of pregnancy by itself, it is a
milestone that is noted by many obstetricians and is
a good way to roughly judge the gestational age of the
pregnancy.318 PREGNANCY