what-when-how
In Depth Tutorials and Information
CHAPTER
26
Osteogene
sis Imperfecta and
Pregnancy
Deborah Krakow
David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
INTRODUCTION
aortic stenosis. This type of hypertrophy enables the
heart to enhance its pumping capacity and makes the
pregnant heart mechanically efficient.2,3
2,3
Most of these
changes begin early in the first trimester and peak
by 30 to 34 weeks' gestation. The left side of the heart
may increase by almost 50% over non-pregnant values.
Twin pregnancies increase myocardial hypertrophy and
end-diastolic ventricular measurements even further.
4
These changes can take 6 months to regress to normal
and it should be recognized that cardiac compromise
could occur in the postpartum period in an at-risk
individual.
5
One of the most impressive adaptions of pregnancy
is the tremendous increase in cardiac output
.
Cardiac
output is the product of stroke volume and heart rate,
both of which increase in pregnancy and contrib-
ute to the overall increase in output. It increases at
the beginning of the first trimester and by 34 weeks it
has increased by 50% over pre-pregnancy values of
4.88 L/min to 7.34 L/M,
6
respectively. In twin gestations
it increases an additional 20%.
4
During both vaginal
and elective cesarean deliveries, there is an additional
30% increase in cardiac output, returning to pre-deliv-
ery levels in about 1 hour after delivery. In an individ-
ual with cardiac compromise, the period surrounding
delivery and immediately postpartum increase the risk
of morbidity and those patients need to be carefully
monitored.
The changes in cardiac output are of concern in
individuals with underlying cardiac dysfunction and
include those with disease and diminished ejection
fractions. In the more severe forms of OI, while rela-
tively rare, there is a small but documented incidence
of aortic and mitral valvular disease.
7
The disease pri-
marily affects left sided structures and the most prev-
alent lesion is aortic root dilatation. The American
College of Cardiology (ACC) has published guide-
lines on the management of valvular heart disease that
Understanding the appropriate management of preg-
nancy in women with osteogenesis imperfecta (OI)
is of concern to both the individuals and their physi-
cians. Historically, there was concern in the medical
community over pregnancy outcomes in women of
short stature due to high complication rates, whether
the underlying genetic disorders could be passed on to
their offspring and management of delivery. Through
experience and patient advocacy, increasing numbers of
women with significant short stature due to numerous
genetic disorders including OI have achieved success-
ful pregnancy outcomes. Pregnancy causes numerous
physiologic changes and adaptions that can exacerbate
already stressed organ systems. Appreciation for nor-
mal physiologic changes should be understood and
incorporated in the management of a pregnant woman
with OI. For most patients with OI, cardiovascular pul-
monary and skeletal systems may be adversely affected.
C
ARDIOVASCULAR SYSTE
M
Pregnancy causes significant physiologic modifica-
tions in the cardiovascular system. Numerous changes
start as early as 5 weeks in order to provide oxygen to
both fetal and maternal tissues.
1
In most women these
changes are easily tolerated, though if there is underly-
ing cardiac compromise, morbidity and mortality can
arise.
In pregnancy, by late gestation the diaphragm is
superiorly displaced by almost 4 cm.
There is expanded blood volume in the first half of
pregnancy and later in gestation there is increased after-
load. This leads to an eccentric hypertrophy, as seen in
changes induced by exercise, as opposed to concentric
hypertrophy that is seen in chronic hypertension and
