32 Obstetrics and Gynecology Board Review •••
❍ Can a pericardial effusion be normal in pregnancy?
Yes. Small effusions are considered normal in pregnancy.
❍ Stroke volume increases during pregnancy. Is this a function of an increased inotropic effect?
No. Increased stroke volume in a singleton pregnancy is directly proportional to the increased end-diastolic volume
caused by increased blood volume (Starling phenomenon). In multifetal pregnancies, however, there has been a
positive inotropic effect demonstrated to further increase stroke volume.
❍ What is the prepregnancy stroke volume compared with the pregnancy stroke volume?
Normal prepregnancy stroke volume is about 60 mL. This increases to about 70 mL in pregnancy. Remember:
stroke volume = cardiac output/heart rate.
❍ What normal changes could you see on an EKG during pregnancy?
Left axis deviation, absent Q wave in aVf, T wave flattening or inversion in lead III. All of these are caused by the
positional shift of the heart. The rhythm may be irregular as atrial and ventricular extrasystoles are common.
❍ What are the normal changes in the auscultative heart examination during pregnancy?
Exaggerated split S1 with increased loudness of both components, systolic ejection murmurs heard at the left
sternal border are present in 90% of patients, soft and transient diastolic murmurs are heard in 20%, and
continuous murmurs from breast vasculature are heard in 10%. The significance of murmurs in pregnancy must
be carefully evaluated and clinically correlated. Harsh systolic murmurs and all diastolic murmurs should be taken
seriously and worked up before being attributed to pregnancy.
❍ Why is the erythrocyte sedimentation rate (ESR) not a useful test during pregnancy?
The ESR is elevated normally during pregnancy for unclear reasons. A plausible explanation is the increased
clumping of red cells caused by increased levels of fibrinogen and globulin. The elevation is different between
whole blood samples and citrated blood samples. For whole blood (red top tube) the mean is 78 mm/h with a
range of 44 to 114 mm/h. For citrated blood (purple top tube) the mean is 56 mm/h with a range of 20 to
98 mm/h.
❍ Plasma volume and blood volume increase in pregnancy. By how much and at what gestational age, does the
volume increase?
Increase (%) Gestational Age Plateau
Plasma volume 40–60% 12–36 weeks 34–36 weeks
Blood volume (plasma
and erythrocytes)45% 24–28 weeks (peak) starts
in first trimester34–36 weeks❍ Which three clotting factors decrease during pregnancy?
- Factor XI.
- Factor XIII.
- Antithrombin III (antifactor Xa).