Strengths and limitations
The main strengths of the FMF study are first, prospective examination
of a large population of women with singleton pregnancies attending for
routine pregnancy care at 11-13 weeks’ gestation, second, we recorded
maternal and pregnancy characteristics that have previously been
reported to be associated with development of hypertensive disorders of
pregnancy, third, we used a recently updated definition of PE which
requires the development of hypertension with either proteinuria or
renal insufficiency, hepatic dysfunction, thrombocytopenia, neurological
complications or pulmonary edema,28 and fourth, we
carried out multiple logistic regression analysis and found that
significant independent contribution to PE, in addition to racial
origin, was provided by maternal age, weight, height, method of
conception, smoking, history of chronic hypertension or diabetes,
parity, family history of PE, previous pregnancy affected by PE or birth
of small for gestational age neonate.
A limitation of the FMF study is that racial origin was classified into
five broad categories and it is likely that there would be variations in
outcome in subgroups within each category, such as different regions of
Africa and between African and Caribbean women classified as black.
The main limitations of the study relate to the findings of the
systematic review of the literature and meta-analysis. For example, 16
studies provided data on the comparison of the incidence of PE between
black and white women and although in most the incidence in black women
was higher, the heterogeneity between studies was 98%; furthermore,
only two of the studies reported adjusted ORs and adjustments were made
for very few of the maternal characteristics. Similarly, there were only
seven studies reporting on South Asian women and five on East Asian
women, by comparison with white women and only two of these studies
reported adjusted ORs. Consequently, although the combined data included
more than 800 thousand black women and more than two million white
women, the meta-analysis does not provide useful information on the true
contribution of black race to the prediction of PE because of the
heterogeneity between studies and the lack of adjustment for confounders
in most of the studies; the same is true for women of South Asian and
East Asian racial origin.