Table 3 Characteristics and risk factors reported in included studies

 Mohamed et al.1998 [15]

Harare, Zimbabwe

338

144 cases, 194 controls

Women who delivered at Harare hospital maternity from June 1995 to April 1996, recruited from admission and birth records.

Controls were normotensive pregnant women delivering within two hours and were matched in childbirth mode with the case.

American College of Obstetricians and Gynecologists definition

Blood pressure > 140/90 mmHg at least twice and occasional proteinuria > 1 g/l at least twice at 4 h intervals.

Age, overweight, obesity.

Overweight OR 7 (2.9–19.4)

 Anorlu et al. 2005 [6]

Lagos, Nigeria

368

128 cases, 240 controls

Delivered women at Lagos university hospital from February 2001 to August 2002 with preeclampsia or eclampsia.

The randomly selected controls were women who gave birth at 24–48 h intervals without preeclampsia. For each case, two controls were selected.

Blood pressure > 140/90 mmHg at least twice on two occasions at least 4 h apart with either 24 h proteinuria ≥300 mg or urinary protein strip with ≥1+ protein in the absence of urinary tract infections.

Age, parity, educational level, occupation, home and work environment, family history of hypertension, chronic hypertension, previous preeclampsia.

Chronic hypertension

OR 2.21 (1.17–6.20)

 Kiondo et al. 2012 [16]

Mulago, Uganda

557

207 cases, 352 controls

Pregnant women aged 15 to 39 randomly selected from computer database from May 1, 2008 to May 1, 2009 living within 15 km of Mulago hospital and more than 20 weeks pregnant.

Women with cardiac disease, sickle cell disease, eclampsia, HELLP syndrome and renal failure were excluded from controls. For each identified case, two controls were selected on the same day until the required number of patients was obtained.

Blood pressure > 140/90 mmHg at least twice on two occasions at least 4 h apart with either 24 h proteinuria ≥300 mg or random proteinuria ≥1+

Age, educational level, marital status, smoking status, alcohol intake, MUAC, history of diabetes, hypertension, family history of hypertension, parity.

Chronic hypertension

OR 2.29 CI (1.12–4.66)

 Guerrier et al. 2013 [14]

Jahun, Nigeria

1676

419 cases (175 severe PE, 244 eclampsia), 1257 controls

Pregnant women admitted from October 2010 to May 2011.

Severe PE: Blood pressure > 160/110 mmHg and random proteinuria ≥2+

Age, ethnicity, occupation, personal history of PE, history of hypertension, family history of PE and hypertension, number of ANC visits.

Chronic hypertension

OR 10.5 (5.8–19)

 Endeshaw et al. 2016 [17]

Bahir Dar, Ethiopia

453

151 cases, 302 controls

Pregnant women attending or delivered in a referral hospital or six health centers in Bahir Dar between June and September 1994, diagnosed pre-eclamptic by a physician or midwife.

For each case, two controls were randomly selected in the same center on the same day.

Blood pressure > 140/90 mmHg at least twice on two occasions and laboratory-confirmed proteinuria

Age, area of residence, marital status, occupation, MUAC, fruit, vegetable, folate, alcohol and coffee intake, anemia, physical activity.

Obesity

OR 3.33 (1.87–5.79)

 Grum et al. 2017 [18]

Addis Ababa, Ethiopia

291

97 cases, 194 controls

Pregnant women attending the two largest hospitals of Addis Ababa from December 2015 to February 2016 diagnosed pre-eclamptic by an obstetrician. Women with known hypertension, renal disease, with serious medical conditions and those who could not give consent were excluded.

Controls were women not diagnosed with preeclampsia in the two hospitals.

Blood pressure > 140/90 mmHg at least twice on two occasions with either 24 h proteinuria ≥300 mg or random proteinuria ≥1+ after 28 weeks gestation

Age, ethnicity, religion, marital status, occupation, educational status, family history of hypertension, history of eclampsia, gravidity, multiple pregnancy, alcohol, fruit intake.

Alcohol consumption

OR 3.97 (1.8–8.75)

 Kahsay et al. 2018 [19]

Tigray, Ethiopia

330

110 cases, 220 controls

Pregnant women with gestational hypertension or PE diagnosed by an obstetrician in one of the seven hospitals in the Tigray region from June to November 2017.

Women without hypertension were controls, women less than 20 weeks pregnant were excluded. Cases and controls were matched for parity and time of arrival at hospital.

Blood pressure ≥ 140/90 mmHg at least twice associated with proteinuria ≥1+ on the urine test strip

Age, area of residence, marital status, occupation, ethnicity, income category, family history of hypertension, MUAC, BMI, fruit and vegetable intake, coffee use, history of smoking, diabetes mellitus, oral contraceptive use.

Overweight OR 5.5 (1.12–27.6

Diabetes OR 5.4 (1.1–27.0)

 Mrema et al. 2018 [10]

Kilimanjaro, Tanzania

17,738

582 cases, 17,156 controls

Birth records selected women with one previous pregnancy and a monofetal actual pregnancy diagnosed as pre-eclamptic by an obstetrician.

Normotensives pregnant women were controls.

Blood pressure > 140/90 mmHg

associated with 24 h proteinuria ≥300 mg

Age, marital status, occupation, educational level, pregnancy number, number of ANC, chronic hypertension, diabetes, heart disease, BMI.

Overweight OR 1.4 (1.2–1.8)

Obesity OR 1.8 (1.3–2.4)

 Singh et al. 2014 [20]

Sokoto, Nigeria

216

13 PE (6%)

Pregnant women attended Usmanu Danfodiyo University hospital from March to December 2011 at less than 20 weeks pregnancy and were followed-up to 6 weeks after giving birth. The main outcome was the development of hypertensive disorders during the follow-up period.

Blood pressure > 140/80 mmHg associated with proteinuria

Age, marital status, education, occupation, type of gestation, family history of hypertension and diabetes mellitus, history of preeclampsia, BMI.

Obesity RR 2.7 (1.3–5.7)

 Baragou et al. 2014 [21]

Lomé, Togo

Urban

1620

114 PE (7%)

Pregnant women recruited in the gynecology service of Tokoin University hospital from October 1, 2011 to September 31, 2012. The main outcome was hypertensive disorder during pregnancy. Women were followed during the pregnancy to 3 months postpartum.

Blood pressure > 140/90 mmHg at least twice on two occasions at least 4 h apart with either 24 h proteinuria ≥300 mg or urinary protein strip with ≥1+ protein in the absence of urinary tract infection

Age, occupation, multiple pregnancy, stress, obesity, familial history of hypertension, history of preeclampsia.

Chronic hypertension RR 3

Obesity RR 2.8

 Musa et al. 2018 [22]

Jos, Nigeria

307

27 PE (8.8%)

Pregnant women attending the Jos University hospital between November 2010 to August 2011 before 20 weeks pregnancy without any signs of PE. Patients with chronic hypertension, proteinuria, chronic renal failure, diabetes, sickle cell disease were not included.

The primary outcome was preeclampsia and follow-up was terminated at any gestational age if the woman developed preeclampsia or delivery of her baby with or without development of preeclampsia.

Blood pressure ≥ 140/90 mmHg at least twice associated with proteinuria ≥2+ on the urine test strip

Age, gestational age, BMI, previous PE, miscarriages, parity, history of infertility, HIV status.

Obesity RR 3.9 (1.5–10.0)

 Tessama et al. 2013 [23]

Dessie, Ethiopia

475

41 PE (8.6%)

Pregnant women attending prenatal visits in Dessie Hospital between August and September 2013 at more than 20 weeks of pregnancy.

Blood pressure > 140/90 mmHg associated with proteinuria ≥1+ on the urine test strip

Age, marital status, ethnicity, educational level, tobacco, alcohol use, family history of hypertension and diabetes mellitus, history of hypertension, gravidity, parity.

Chronic hypertension

OR 4.3 (1,33-13,9)