Interpretation
Compared to studies reported globally our incidence was a little higher. This is probably due to the inclusion of only high-risk pregnant women in our study, whereas in other studies the comparison was made with normotensive pregnant women. Prediction and Prevention of Preeclampsia and Intrauterine Growth Restriction (PREDO) Project, a study conducted among 972 pregnant women in the Finnish population with risk factors for PE reported the incidence of PE among women with previous preeclamptic pregnancy and BMI of >30kg/m2was 28.6%, and among the pregnant women with chronic hypertension and one or more risk factors, the incidence was 24.6%8. A US-based study conducted among the high-risk cohort of pregnant women who received skilled home nursing, reported an incidence of 26.9%9. Out of various factors we studied, the absence of a family history of chronic hypertension, history of abortion, non-consanguineous marriage and maternal blood group being AB-type were reported as significant protective factor and sex of the new-born being female was found to be the risk factor for PE. The possible reason for the development of PE in 67/174 high-risk pregnant women is mainly due to five major factors like a family history of chronic high blood pressure, absence ofa history of abortion, consanguineous marriage, maternal blood group other than ‘AB’ and sex of the new-born.
History of abortion was found to be a protective factor in this study. No studies reported among the high-risk group, but within the pregnant women, various studies reported that prior abortion as a protective factor from developing PE10,11. Analogous to our findings, previous studies have reported the protective effect of both induced10–14 and spontaneous abortions12,15,16. The reason is unclear. But the decreased risk of PE in women with a history of abortion might be due to the longer periods of sexual cohabitation17, thereby the protective factors like transforming growth factor β (TGF-β) present in the seminal plasma might have caused the immune-deviating effects that enhanced the foetal/placental development which further decreased the risk of PE18–22. In contrast to our findings, Trogstad et al. reported an increased risk of PE in women with a history of spontaneous abortions13. This might be due to the association of spontaneous abortions with infertility, which is the potential independent risk factor for PE23.Our finding of the absence ofa family history of chronic hypertension as a protective factor from developing PE is supported by a Brazilian study24. Another study proved that the frequency of PE is greater in women who had hypertension for at least four years and also in those with PE during a previous pregnancy25.
The culture of marrying within the blood relations is more prevalent in south India26and women in consanguineous unions are more likely to have adverse pregnancy outcomes including stillbirth and abortion27,28.Consanguineous marriages continue to be a critical predictor of adverse pregnancy outcomes in India29. Out of many studies attempted to find the association between PE and consanguinity30–32, only a few studies reported an increased risk of PE in marriages with biological relatives33.Though the exact reason is not clear, consanguinity could allow more chance for homozygosity for the same single recessive gene for mother and foetus and consequently more chance for PE.
An important finding of the current study is the protective relation between blood group AB (non-O) and PE. Our finding contradicts a population-based nested case-control study that demonstrated AB blood group as a risk factor forPE34 and a large Swedish cohort study that showed blood group O as a protective factor against PE35. Similar to our findings, Amin et al reported blood group O as a risk factor36 and a contradictory finding by Francine et al., reported non-O blood groups as risk factors while blood group O is protective against PE37.