We identified publications investigating the association between pre-eclampsia and at least one risk factor in a previous pregnancy or in the current pregnancy. We examined those risk factors described in the published guidelines and reviews13 (link)
14 (link)
15 (link)
16 (link)
17 (link)
18 (link)
19 (link) that were patient specific, that were readily recalled by a woman or abstracted from her prior pregnancy record, and that a general clinician could ascertain in the first trimester of pregnancy. For these reasons, and the observation that a family history in risk assessment tends to have a low sensitivity (that is, low recall),20 (link) we did not assess family history of pre-eclampsia as a risk factor. We also limited our selection to large sample cohort studies because they tend to be more representative of the general population than small single centre studies and they have sufficient statistical power to assess less prevalent, but potentially important, risk factors.21 (link)
Selected risk factors from a previous pregnancy included a history of pre-eclampsia, placental abruption, fetal intrauterine growth restriction, and stillbirth.
Current pregnancy risk factors included nulliparity, advanced maternal age, high body mass index (BMI), chronic hypertension, prepregnancy diabetes mellitus (type 1 or type 2), chronic kidney disease, systemic lupus erythematosus, antiphospholipid antibody syndrome, assisted reproduction, and multiple pregnancy.
The resulting papers were first screened by title and abstract. Full text articles were obtained if they met all of the following screening criteria: a cohort study design with a minimum sample size of 1000 pregnancies; the study evaluated the relation between one or more of the aforementioned risk factors and the outcome of pre-eclampsia; the authors provided the number of pre-eclampsia events among their participants with and without a given risk factor, to enable the calculation of pooled effect sizes, as described below.
Full text papers were included in the final dataset if they met the aforementioned screening criteria and also evaluated each risk factor up to 16 weeks’ gestation or earlier (as aspirin might be more efficacious when initiated before this gestational age6 (link)
7 (link)
8 (link)).
Two authors (EB and KM), both of whom are medical students, screened studies and abstracted data. EB screened all citations retrieved from the database searches, and both authors evaluated the eligibility of the full text articles. Disagreements were resolved by discussion or in consultation with a third author (JGR). If two published studies evaluated the same cohort of women, we included the study with the largest number of women or the greatest number of relevant outcomes. Study authors were not contacted.
14 (link)
15 (link)
16 (link)
17 (link)
18 (link)
19 (link) that were patient specific, that were readily recalled by a woman or abstracted from her prior pregnancy record, and that a general clinician could ascertain in the first trimester of pregnancy. For these reasons, and the observation that a family history in risk assessment tends to have a low sensitivity (that is, low recall),20 (link) we did not assess family history of pre-eclampsia as a risk factor. We also limited our selection to large sample cohort studies because they tend to be more representative of the general population than small single centre studies and they have sufficient statistical power to assess less prevalent, but potentially important, risk factors.21 (link)
Selected risk factors from a previous pregnancy included a history of pre-eclampsia, placental abruption, fetal intrauterine growth restriction, and stillbirth.
Current pregnancy risk factors included nulliparity, advanced maternal age, high body mass index (BMI), chronic hypertension, prepregnancy diabetes mellitus (type 1 or type 2), chronic kidney disease, systemic lupus erythematosus, antiphospholipid antibody syndrome, assisted reproduction, and multiple pregnancy.
The resulting papers were first screened by title and abstract. Full text articles were obtained if they met all of the following screening criteria: a cohort study design with a minimum sample size of 1000 pregnancies; the study evaluated the relation between one or more of the aforementioned risk factors and the outcome of pre-eclampsia; the authors provided the number of pre-eclampsia events among their participants with and without a given risk factor, to enable the calculation of pooled effect sizes, as described below.
Full text papers were included in the final dataset if they met the aforementioned screening criteria and also evaluated each risk factor up to 16 weeks’ gestation or earlier (as aspirin might be more efficacious when initiated before this gestational age6 (link)
7 (link)
8 (link)).
Two authors (EB and KM), both of whom are medical students, screened studies and abstracted data. EB screened all citations retrieved from the database searches, and both authors evaluated the eligibility of the full text articles. Disagreements were resolved by discussion or in consultation with a third author (JGR). If two published studies evaluated the same cohort of women, we included the study with the largest number of women or the greatest number of relevant outcomes. Study authors were not contacted.
