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