Pregnancy, parturition and preeclampsia in women of African ancestry

Annettee Nakimuli, Olympe Chazara, Josaphat Byamugisha, Alison M Elliott, Pontiano Kaleebu, Florence Mirembe, Ashley Moffett, Annettee Nakimuli, Olympe Chazara, Josaphat Byamugisha, Alison M Elliott, Pontiano Kaleebu, Florence Mirembe, Ashley Moffett

Abstract

Maternal and associated neonatal mortality rates in sub-Saharan Africa remain unacceptably high. In Mulago Hospital (Kampala, Uganda), 2 major causes of maternal death are preeclampsia and obstructed labor and their complications, conditions occurring at the extremes of the birthweight spectrum, a situation encapsulated as the obstetric dilemma. We have questioned whether the prevalence of these disorders occurs more frequently in indigenous African women and those with African ancestry elsewhere in the world by reviewing available literature. We conclude that these women are at greater risk of preeclampsia than other racial groups. At least part of this susceptibility seems independent of socioeconomic status and likely is due to biological or genetic factors. Evidence for a genetic contribution to preeclampsia is discussed. We go on to propose that the obstetric dilemma in humans is responsible for this situation and discuss how parturition and birthweight are subject to stabilizing selection. Other data we present also suggest that there are particularly strong evolutionary selective pressures operating during pregnancy and delivery in Africans. There is much greater genetic diversity and less linkage disequilibrium in Africa, and the genes responsible for regulating birthweight and placentation may therefore be easier to define than in non-African cohorts. Inclusion of African women into research on preeclampsia is an essential component in tackling this major disparity of maternal health.

Keywords: evolutionary selective pressure; great obstetric syndromes; length of gestation; obstetric dilemma.

Copyright © 2014 Mosby, Inc. All rights reserved.

Figures

Figure 1
Figure 1
Maternal KIR/fetal HLA-C interactions at the site of placentation In these 2 scenarios, the mother is HLA-C1 homozygous and the fetus has inherited an HLA-C2 group allele from the father. If the mother has a KIR AA genotype that lacks activating KIR and has a strong inhibitory KIR for HLA-C2 (KIR2DL1), poor placentation results. In contrast, if the mother has a KIR AB or BB genotype containing the activating KIR for HLA-C2 (KIR2DS1), uterine natural killer cells are triggered to produce increased amount of cytokines and chemokines (eg, granulocyte-macrophage colony–stimulating factor) that enhance placentation. Nakimuli. Pregnancy, parturition and preeclampsia in Africa. Am J Obstet Gynecol 2014.
Figure 2
Figure 2
Birthweight and neonatal mortality rates (n = 13,730). Nakimuli. Pregnancy, parturition and preeclampsia in Africa. Am J Obstet Gynecol 2014.

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