Table 1. Characteristics of included studies
Author, year	Methods	Participants, period	Findings
Nejdet, 2016	Retrospective cohort study	Women from IVF Swedish clinics, from 2003 to 2012	Donor oocyte group consisted of 388 patients, 51 with PE (13.14%). In the control group, 1,105/26,696 (4.14%) had PE. OR 9.059 (95% CI:5.518 to 14.874). Weight: 41.31.
Van Dorp, 2014	Retrospective cohort study	Women from the Dutch Perinatal Register, from 1992 to 2009	Study group consisted of 61 patients with singleton pregnancies. 8 out of 61 had PE (13.11%). The control group had 21/192 (10.94%) cases of PE. OR 1.238 (95% CI:0.502 to 3.053). Weight 12.47.
Levron, 2014	Retrospective cohort study	From 2005 to 2011.	13 of 139 patients in the donor oocyte group had PE (9.35%). In the autologous oocyte group, 6 of 126 had PE (4.76%). OR 1.988 (95% CI:0.782 to 5.052). Weight 11.67.
Malchau, 2013	Retrospective cohort study	Women from the Danish in vitro fertilization register, from 1995 to 2010.	The donor oocyte group included 215 patients and 21 cases of PE (9.76%). Control group had 316/9.833 (3.21%) with PE. OR 7.551 (95% CI:3.565 to 15.993). Weight 18.03.
Stoop, 2012	Retrospective cohort study	Matched pair-analysis for age, ethnicity, parity and plurality from the Centre for Reproductive Medicine,Brussels. Data obtained from 1999 to 2008.	Donor oocyte had 15 of 148 pregnant women diagnosed with PE (10.13%). Control group had 8 of 148 (5.4%) with PE. OR 1.930 (95% CI:0.825 to 4.515). Weight 14.07.
Salha, 1999	Retrospective cohort study	Women from St. James's University Hospital, Leeds(UK), from 1992 to 1997	Donor oocyte group had 3 of 22 patients diagnosed with PE (13.63%). In the control group, only 1 pregnant woman of 26 was diagnosed with PE (3.8%). OR 3.508 (95% CI:0.459 to 26.781). Weight 2.46.