Relation between infants' birth weight and mothers' mortality: prospective observational study
BMJ 2000; 320 doi: https://doi.org/10.1136/bmj.320.7238.839 (Published 25 March 2000) Cite this as: BMJ 2000;320:839
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The paper of Smith et al is suggestive of intergenerational
influences on birthweight and cardiovascular disease risk. Some support
for such intergenerational programming effects can be provided by studies
of animal models.
We have successfully demonstrated that, in rats and mice, the feeding
of a low protein diet in pregnancy induces fetal growth impairment and
lifelong high blood pressure in the resulting offspring. When these first
generation offspring were themselves mated, without any further dietary
manipulations, we noted evidence of intergenerational transmission of
effects on blood pressure (1). When low protein exposed, hypertensive
males were mated with control females the resulting offspring also had
raised blood pressure as adults. In contrast to the evidence presented by
Smith et al, there appeared to be no transmission of hypertension through
the female line.
Much earlier studies by Beach and coworkers (2) suggested that the
immune system could also be influenced by short-term dietary manipulations
across several generations. Studies of mice indicated that the offspring
of zinc restricted mothers transmitted depressed immune functions across
two subsequent generations.
1. S.C.Langley-Evans, R.L. Dunn, A.A. Jackson (1998). Blood pressure
changes programmed by exposure to maternal protein restriction are
transmitted to a second generation through the germ line. Proceedings of
the Nutrition Society 57 78A
2. R.S. Beach, M.E. Gershwin, L.S. Hurley (1982). Gestational zinc
deprivation in mice: persistence of immunodeficiency for 3 generations.
Science 218 469-471
Competing interests: No competing interests
Smith, Harding, and Rosato do not mention the most likely explanation
for the strong negative association between fetal growth and maternal
cardiovascular disease. This is the cardiovascular feat that is inherent
in carrying a normal pregnancy. Investigators have found that the
difference between cardiac performance between trained athletes and couch
potatoes disappear during pregnancy: the latter increase their end
diastolic volume, stroke volume and cardiac output maxima to equal the
former.
A normal pregnancy is the equivalent, in cardiac output and
ventilatory volume, of a 10,000 km walk.
The maximum perfusion to the normal uterus increases by 1000 to 1500
percent over about six months, challenging any impairment of the vascular
system. It is well know that hypertensives and diabetics with vascular
disease are prone to having small babies.
It is apparent that the outcome of this stress test in infant birth
weight is a more sensitive test of this system than other measures
available to the authors.
My only question is does this apply to "gestational diabetics", whose
sugars we try to control carefully. If we were more relaxed about this
would they then live longer?
James S. SMeltzer, MD
Competing interests: No competing interests
Can we predict mothers' mortality by baby's brith weight?
Sir- Dr. Smith's report on the relation of baby's birth weight and
mothoer's mortality raised a perlex question: Could we depend on how much
a baby born by a mother to predict the mother's mortality in the next ten
or even more years? Absolutely no! There ara some fatal errors in analysis
the data.Dr Smith has pooled the data by baby's birth weight,that mean,he
infact are doing a cross sectional research in fact,the correlation are
only correlation,has limited meaning in practice.The best way to pool the
data is first to catagorise mother's status(dead of alive at the endpoint
of observation) and then to assess wheather the baby's weight different
between those dead and still alived mothers.This method perhap can offer
more surport to the researchers' points.
Clayman ZK Zhang
Competing interests: No competing interests