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.