Physiologic and Supraphysiologic Increases in Lipoprotein Lipids ...

416 ARTERIOSCLEROSIS VOL 4, No 4, JULY/AUGUST 1984
A final argument that a supraphysiologic rise in
plasma triglyceride antepartum is a pathophysiologic
process signifying an underlying prelipemic trait is
based on the fact that all three subjects for whom
relatives were available show evidence of hyperlipidemia
among family members. The difference
among the subjects' responses to pregnancy, as well
as the available information among relatives, suggests
that the designation of prelipemia could represent
several distinct and possibly genetic underlying
disorders of lipoprotein metabolism. Further investigations
of larger numbers of prelipemic women with
in-depth family studies are necessary to resolve this
question. In addition, long-term follow-up will be necessary
to verify the hypothesis that the hyperlipidemic
stress of pregnancy can unmask a prelipemic
trait. Nonetheless, it is noteworthy that subject CB
has remained hyperlipidemic for almost 2 years
since delivery, her only normal value having been
obtained before the pregnancy we observed.
While the postpartum observations made at specific
times and the distinctions between subjects with
physiologic and supraphysiologic lipid increases in
pregnancy are entirely new, our antepartum observations
confirm several previously described features
of hyperlipidemia in pregnancy. These include
an increase in total and VLDL apo B, 24 little or no
change in VLDL composition, 2 2425 an increase in
triglyceride content of LDL and HDL, 22425 and an
increase in apo A-l. 26 Thus, conclusions drawn from
this paper can be considered to be generally representative
of the body of information on hyperlipidemia
in pregnancy.
The possibility that the hyperlipidemia of pregnancy
might confer added arteriosclerosis risk has
recently been raised. 2728 While it is true that an increase
in LDL cholesterol could enhance arteriosclerosis,
usually this change is associated with an apo
B-rich 29 and triglyceride-poor LDL, 30 which is the opposite
of that seen in pregnancy. In addition, HDL
cholesterol and apo A-l concentrations were increased,
which may facilitate cholesterol removal
from tissues. In light of these results, it is perhaps not
surprising that the epidemiologic evidence 31 that
arteriosclerosis is more common in multiparous
women is inconclusive. It is more likely that the observed
lipoprotein changes serve a physiological
purpose to support growth of maternal and fetal tissues
and production of large quantities of steroid
hormones. 5 ' 16 The extent to which the postpartum
lipoprotein changes are atherogenic is deserving of
further study.
In summary, evidence is presented to support the
hypothesis that the hyperlipidemic stress of pregnancy
can unmask a latent hypertriglyceridemia, by
using as a basis for recognition a triglyceride rise in
pregnancy exceeding the 95th percentile. Women
with such a supraphysiologic triglyceride rise antepartum
may return to normal levels postpartum more
slowly than normal, have LDL lipids that change in an
atypical manner antepartum and postpartum, have
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HDL cholesterol concentrations that are persistently
low antepartum and postpartum, and have hyperlipidemic
family members. In contrast, hypercholesterolemia
is not greatly exaggerated in pregnancy. Longterm
follow-up studies of women with genetically
well-characterized disorders of lipoprotein metabolism
are required to determine if an abnormal lipoprotein
response in pregnancy can identify prelipemic
subjects and distinguish among the major disorders
of lipoprotein metabolism. Identification of prelipemia
will provide an opportunity to study prospectively
the natural progression, potential for atherosclerosis,
and possible treatment of hyperlipidemia from
early adulthood.
Acknowledgments
The authors express their thanks to the staff of the Northwest
Liptd Research Clinic Core Laboratory who performed analyses;
to Susan Irvine who carefully obtained the samples; to the gracious
women of the Childbirth Education Association who volunteered
for participation in the study; and to Donna Gola and Lori
Lebon for excellent secretarial assistance.
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