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Obstetrics
Lee. 2 د. بان عامر موسى
ةعبارلا ةلحرملا
Pregnancy Diagnosis
The diagnosis of pregnancy requires a multifaceted approach
using 3 main diagnostic tools. These are history and physical
examination, laboratory evaluation, and ultrasonography.
Currently, physicians may use all of these tools to diagnose
pregnancy at early gestation and to help rule out other
pathologies.
History and Physical Examination
The diagnosis of pregnancy has traditionally been made based
on history and physical examination findings. Important aspects
of the menstrual history must be obtained. The woman should
describe her usual menstrual pattern, including date of onset of
last menses, duration, flow, and frequency. Items that may
confuse the diagnosis of early pregnancy are an atypical last
menstrual period, contraceptive use, and a history of irregular
menses. Additionally, as many as 25% of women bleed during
their first trimester.
The classic presentation of pregnancy is a woman with menses
of regular frequency who presents with amenorrhea, nausea,
vomiting, generalized malaise, and breast tenderness.
Abdominal enlargement, caused by the growing uterus,
reaches the umbilicus by 20 weeks’ gestation. Fetal movement
can usually be perceived by 18 weeks' gestation. Breast
tenderness, nausea, vomiting, and urinary complaints can also
occur. However, physical symptoms are not sufficiently reliable
to diagnose pregnancy.
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Clinical symptoms of pregnancy
Amenorrhea
Abdominal enlargement
Fetal movement
Breast tenderness
Nausea
Vomiting
Urinary complaints
Upon physical examination, one may find an enlarged uterus
after bimanual examination, breast changes, and softening and
enlargement of the cervix (Hegar sign; observed at
approximately 6 wk). The Chadwick sign is a bluish
discoloration of the cervix from venous congestion and can be
observed by 8-10 weeks. A gravid uterus may be palpable low
in the abdomen if the pregnancy has progressed far enough,
usually by 12 weeks.
Laboratory Evaluation
Several hormones can be measured and monitored to aid in
the diagnosis of pregnancy. The most commonly used assays are
for the beta subunit of hCG. Other hormones that have been
used include progesterone and early pregnancy factor.
Beta-human chorionic gonadotropin
hCG is a glycoprotein similar in structure to follicle-
stimulating hormone (FSH), luteinizing hormone (LH), and
thyrotropin. hCG is composed of alpha and beta subunits. The
alpha subunit of hCG is similar to the alpha subunit of FSH, LH,
and thyrotropin. The free beta subunit of hCG differs from the
others. Detection of hCG in the plasma is not possible until
implantation has occurred, approximately 10 days after the LH
surge. Typically, the level of (3-hCG doubles approximately
every 36 hours and peaks at about 100,000 mlU/ml at 10 weeks'
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gestation, after which it decreases to about 20,000 mlU/ml by
midpregnancy, where it remains until term. (3-hCG is not
diagnostic of only normal pregnancy . Abnormal elevations,
plateaus, or decreasing titers of p-hCG raises the possibility of
ectopic pregnancy or miscarriage. The use of the assay in this
context typically requires other modalities such as ultrasound,
serum progesterone levels, or both.
Serial hCG monitoring
The initial rate of rise, measured by serial quantitative hCG
testing, is important in the monitoring of early complicated
pregnancies that have yet to be documented as viable and/or
intrauterine. Failure to achieve the projected rate of rise may
suggest an ectopic pregnancy or spontaneous abortion. hCG
doubling times are subject to fluctuations of intact hCG during
early pregnancy, so interpretation of these values must take into
account the assays used and the clinical picture.
On the other hand, an abnormally high level or accelerated rise
can prompt investigation into the possibility of molar pregnancy,
multiple gestations, or chromosomal abnormalities.
Progesterone
Measuring serum progesterone may be a useful adjunct for
evaluating abnormal early pregnancy. Serum progesterone is a
reflection of progesterone production by the corpus luteum,
which is stimulated by a viable pregnancy. Measurement of
serum progesterone is inexpensive and can reliably predict
pregnancy prognosis. Viable intrauterine pregnancy can be
diagnosed with 97.5% sensitivity if the serum progesterone
levels are greater than 25 ng/mL (>79.5 nmol/L). Conversely,
finding serum progesterone levels of less than 5 ng/mL (< 15.9
nmol/L) can aid in the diagnosis of a nonviable pregnancy with
100% sensitivity.
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Ultrasonography
With the advent of transvaginal ultrasonography (TVUS), the
diagnosis of pregnancy can be made even earlier than is possible
with transabdominal ultrasonography (TAUS). US has long
been used in uncomplicated pregnancies for dating and as a
screening examination for fetal anomalies. US is not typically
used to diagnose pregnancy unless the patient presents with
vaginal bleeding or abdominal pain early in gestation or is a
high-risk obstetric patient. TVUS is the most accurate means of
confirming intrauterine pregnancy and gestational age during the
early first trimester.
TVUS has several advantages over TAUS during early
pregnancy. TVUS can help detect signs of intrauterine
pregnancy approximately 1 week earlier than TAUS. Patients
are not required to have a full bladder and are not required to
endure uncomfortable pressure on the abdominal wall from the
external probe. TVUS is also better for patients who are obese
or those who guard during TAUS. One disadvantage is that
some patients are anxious about the transvaginal probe and may
object to its insertion.
Ultrasonography and Human Chorionic Gonadotropin
Ultrasonography becomes even more useful for the diagnosis
of early pregnancy and for identifying abnormal pregnancies
when it is used in conjunction with assessing quantitative hCG
levels. The identification of gestational structures by
ultrasonography correlates with specific levels of hCG, termed
discriminatory levels. A discriminatory level is the level of hCG
at which the structure in question should always be identified.
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Summery
The diagnosis of pregnancy can be made by several methods.
Normocyclic women who present with amenorrhea and typical
history and physical examination findings have the classic
presentation and can be diagnosed with a viable intrauterine
pregnancy if they progress appropriately. Currently, most
women are diagnosed with pregnancy after a missed menstrual
cycle and a positive urine or serum hCG finding. The pregnancy
is diagnosed as viable with serial examinations and normal
pregnancy development, a normal result after dating
ultrasonography, or a positive finding of fetal heart tones using
Doppler studies.
Women who are considered high-risk or those who present
with abdominal pain or vaginal bleeding in early gestation are
more likely to be evaluated with ultrasonography and additional
hormonal assays. A number of different combinations can aid in
the diagnosis of a viable intrauterine pregnancy. The physician
must ascertain what is most appropriate at the time of patient
presentation.