Obstetric Management
TESTS OF FETAL WELL-BEING
Pregnancies complicated by gestational diabetes are at
increased risk of stillbirth (2 ). Although there is no
single best evidence-based approach to monitoring fetal
well-being in gestational diabetic pregnancies, the
ACOG has stated: “Despite the lack of conclusive data,
it would seem reasonable that women whose GDM is
not well controlled, who require insulin, or who have
other risk factors such as hypertension or adverse obstetric
history should be managed the same as individuals
with preexisting diabetes. The particular antepartum
test selected, whether nonstress test, contraction
stress test, or biophysical profile, may be chosen according
to local practice” (34 ). In our institution GDM
mothers with risk factors noted above begin twice
weekly nonstress tests and amniotic fluid indices at between
32 and 36 weeks, depending upon the severity of
the risk factors. Those with no risk factors and whose
circulating glucose concentrations are within targets,
using medical nutrition therapy alone, start weekly
testing at 36 weeks.
FETAL GROWTH
The rate of macrosomia in GDM varies, depending
upon the diagnostic criteria and the method of treatment.
In a randomized trial of identification and treatment
of mild forms of GDM, macrosomia (birthweight
4000 g) was present in 21% (27 ) and 14% (28 ) of
untreated pregnancies, which was about twice the rate
in each study in pregnancies in which GDM was identified
and treated. Because GDM is associated with fetal
macrosomia, and macrosomia in a fetus of a diabetic
mother is associated with an increased risk of shoulder
dystocia compared to the risk in a similar-weight fetus
of a nondiabetic mother, normalization of maternal
glucose is the most important means of prevention of
this problem. However, such efforts are not always successful,
and large babies are sometimes born to mothers
whose GDM is well controlled. Therefore periodic
ultrasound imaging of the fetus is used to estimate fetal
weight and growth trajectory. Caution should be exercised
in interpreting ultrasound fetal weight estimations
because the range of error is relatively wide. One
series of investigations has demonstrated the successful
use of ultrasound estimates of fetal growth trajectories
to determine which GDM mothers may or may not
benefit from insulin treatment with (57 ) or without
(58 ) increased fasting glucose concentrations.