Data sources
The search identified 3,654 potentially relevant citations, but 3,635
were excluded because they were non-relevant articles, abstracts or
letters rather than peer-reviewed papers, case-control studies, review
articles, opinions or guidelines, studies providing data on a mixture of
singleton and twin pregnancies or a mixture of PE and GH, and studies on
parts of the same population (Figure 1). In total, only 19 studies were
considered to be relevant and their data were combined with ours for the
meta-analysis4-22. All 20 studies reported on PE in
white women, 17 in black women, 8 on South Asian women and 6 on East
Asian women.