Supplementary Table 1 Additional characteristics of17 studies included in the meta-analysis

Study / Strategies used to identifyHPDs / Diagnostic criteria / Superimposed PE / Quality assessment by NOS scale
Selection / Comparability / Outcomes / Total
Representativeness of exposed cohort / Selection of Non-Exposed Cohort / Ascertainment of exposure / Demonstration that outcome of interest was not present at start of study / Assessment of outcome / Follow-up was long enough / Adequacy of follow up of cohorts
Yuan X 2016 / Secure records / Gestational hypertension is defined as the onset of hypertensionwithout proteinuria after 20 weeks of gestation. / Without superimposed preeclampsia / --※ / * / * / -- / ** / * / * / -- / Good
Heida KY 2015 / Structured interview / HDP was identified by standard questionnaire. / Without superimposed preeclampsia / -- / * / * / * / ** / * / * / * / Excellent
Savitz DA 2014 / Secure records / Gestational hypertension is defined as the onset of hypertensionwithout proteinuria after 20 weeks of gestation, while preeclampsia is referred to as the onset of hypertensionwith proteinuria. / Without superimposed preeclampsia / * / * / * / * / ** / -- / -- / * / Excellent
Kurabayashi T 2013 / Secure records / Gestational hypertension is diagnosed in women whose blood pressure is ≥140/90 mmHg after the 20th gestational week, regardless of proteinuria. Pre-eclampsia is characterized by de novo hypertension and proteinuria. / Without superimposed preeclampsia / * / * / * / -- / * / -- / * / * / Good
Feig DS 2013 / Secure records / Gestational hypertension is defined as the onset of hypertensionwithout proteinuria after 20 weeks of gestation, while preeclampsia is referred to as the onset of hypertensionwith proteinuria. / With superimposed preeclampsia / * / * / * / * / ** / * / -- / * / Excellent
Mannisto T 2013 / Secure records / Gestational hypertension included women who were normotensive before the 20th gestational week but hypertensive after the 20th gestational week, with no proteinuria during pregnancy.
Preeclampsia/eclampsia included women who were normotensive before the 20th gestational week but hypertensive after the 20th gestational week with proteinuria in ≥1 sample. Chronic hypertension included those with hypertension before the 20th gestational week, continuing throughout the pregnancy and/or up to 6 weeks after pregnancy.Superimposed preeclampsia/eclampsia included chronic hy-pertension with proteinuria. / Superimposed preeclampsia as one group / * / * / * / * / ** / * / * / * / Excellent
Wang IK 2012 / Secure records / Gestational hypertension is defined as the onset of hypertension (>140/90 mm Hg) without proteinuria after 20 weeks of gestation, while preeclampsia is referred to as the onset of hypertension ( >140/90 mm Hg) with proteinuria ( >0.3 g/24 hours), also after 20 weeks of gestation. / Without superimposed preeclampsia / * / * / * / * / ** / * / -- / * / Excellent
Engeland A 2011 / Secure records / Preeclampsia was blood pressure > 140/90 after 20 weeks of gestation, combinedwith proteinuria >0.3 g/24 h) (>1 dipsticks) on at least two occasions. / Without superimposed preeclampsia / * / * / * / * / ** / * / -- / * / Excellent
Garovic VD 2010 / Structured interview / HDP was identified by standard questionnaire. Preeclampsia was definedeither by self-report of this condition or byself-report of protein in the urine during thepregnancy with hypertension. / Without superimposed preeclampsia / -- / * / * / -- / -- / -- / * / * / Good
Magnussen EB 2009 / Secure records / Preeclampsia was defined as a sustained increase in blood pressure to at least 140/90 mm Hg after mid gestation, combined with proteinuria of at least 1 or more on a semiquantitative dipstick, which followed the 1972 recommendations of the AmericanCollege of Obstetricians and Gynecologists. Gestational hypertension was defined as blood pressure of 140/90 mmHg or more (one or both values exceeded) or increase in systolic blood pressure of 30 mm Hg or more and diastolic blood pressure of 15 mm Hg or more after mid gestation, without concomitant proteinuria. / Without superimposed preeclampsia / * / * / * / * / ** / -- / * / * / Excellent
Carr DB 2009 / Secure records / Preeclampsia during the indexpregnancy was classified as one occurrenceof any of the following ICD-9 codes assigned duringoutpatient or inpatientvisits associated with the pregnancy: ICD-9 642.4-642.5 (preeclampsia), 642.6(eclampsia), or 646.8(Hemolysis Elevated Liver enzymes Low Platelets,
HELLP, syndrome). / Without superimposed preeclampsia / * / * / * / * / * / ** / -- / * / Excellent
Lykke JA 2009 / Secure records / The hypertensive pregnancy disorders were stratified into gesta-tional hypertension, mild preeclampsia, and severe preeclampsia (including eclampsia and hemolysis, elevated liver enzymes, and low platelets syndrome), which followed AmericanCollege of Obstetricians and Gynecologists criteria / Without superimposed preeclampsia / * / * / * / * / * / * / * / * / Excellent
Callaway LK 2007 / Secure records / HDPwere defined as a diastolic blood pressure of >90 mm Hg on at least 2 occasions beyond 20 weeks of gestation that were associated with proteinuria and/or excessive fluid retention. / With superimposed preeclampsia / * / * / * / * / ** / -- / * / * / Excellent
Libby G 2007 / Secure records / Preeclampsia was defined as a rise in diastolic blood pressure after the 26th week of pregnancy to ≥90 mmHg on two or more occasions separated by at least 1 day, together with confirmed albuminuria. / Unclear / -- / * / * / * / * / -- / * / * / Good
HashemiS 2013 / Structured interview / Hypertensive pregnancy disorders (HPD) were defined as the onset of a blood pressure level exceeding 140/90 mm Hg with or without proteinuria >0.3 g/24 h after 20 weeks’ gestation. / Unclear / -- / * / -- / * / * / -- / * / -- / Good
MarinR 2000 / Secure records / HDP included preeclampsia, eclampsia, and gestational hypertension, which followed the AmericanCollege of Obstetricians and Gynecologists criteria. / Unclear / -- / -- / * / * / -- / -- / * / -- / Suboptimal
SibaiBM 1986 / Secure records / Severe preeclampsia was defined as the presence of blood pressure 160/100 mmHg on two separate occasions, accompanied by either generalized edema or proteinuria (at least 3 or more) on dipstick examination. / Without superimposed preeclampsia / -- / * / * / * / * / -- / -- / * / Good

(Abbreviations: ※--, studies didn’t meet this criteria; NA, not available; HDP, hypertensive disorders during pregnancy; GH, gestational hypertension; GDM, gestational diabetes mellitus; Quality was assigned as excellent with 7-9 stars, good with 4-6 stars, and suboptimal with 0-3 stars.)