Angiogenic factors
During pregnancy, it is well established that, in the general obstetric
population, PLGF is reduced from as early as the first trimester in
pregnancies later complicated by PE and sFLT-1 is increased up to five
weeks prior to the clinical onset of the disease.3However, little is known as to the impact of CH on first trimester serum
PLGF and sFLT-1.
In women with CH, it could be anticipated that the degree of early
placental hypoxia would be greater than in normotensive pregnancies due
to pre-existing endothelial disease with a consequent higher production
of sFLT-1 and lower PLGF. The latter is in keeping with our finding,
along with other studies, of significantly lower first trimester serum
PLGF in women with CH.16 However, we were unable to
demonstrate any differences in first trimester serum PLGF between the
four groups of women with CH despite the differences in the rates of,
particularly preterm, PE. It has previously been shown that, in women
with CH, the distribution of birth weight adjusted for gestational age
at delivery is skewed to the left of the distribution for uncomplicated
pregnancies and that there is an approximate 2-fold increase in the risk
of having a small for gestational age infant even in the absence of
PE.1 Along with our findings, this suggests that CH is
associated with impaired placentation irrespective of the development of
PE.
Our finding of lower sFLT-1 in women with CH who had well-controlled BP
only was difficult to interpret. We postulated that an impaired
placenta, as expected in women with CH, would have less capacity to
produce sFLT-1. However, should this be the case, one would expect low
sFLT-1 in all four groups. It is likely that, although the risk of PE is
not homogenous across all women with CH, alteration in first trimester
serum sFLT-1 does not have a significant role in the later development
of PE and / or, alternatively, our study was underpowered to detect
subtle differences between the four groups. Although there are studies
examining first trimester serum sFLT-1 in women with CH, none of them
included normotensive controls for comparison.9, 17