Table 2.
Summary of included studies.
| Reference | Publication date | Period of intervention | Country of study | Micronutrient supplementation intervention | Screening for pre-eclampsia | Gestational age during intervention |
|---|---|---|---|---|---|---|
| Hofmeyr et al. | 2019 | Prepregnancy into pregnancy | South Africa, Zimbabwe, Argentina | Calcium | Previous pre-eclampsia | From prepregnancy to 20 weeks’ gestation |
| Baba Dizavandy et al. | 1998 | Pregnancy | Iran | Calcium | Positive roll-over test | From 28–32 weeks gestation to delivery |
| Herrera et al. | 1998 | Pregnancy | Colombia | Calcium and linoleic acid | Positive roll-over test and high mean arterial pressure | From 28–32 weeks’ gestation to delivery |
| Niromanesh et al. | 2001 | Pregnancy | Iran | Calcium | Positive roll-over test and at least one risk factor for pre-eclampsia | Until delivery |
| Sanchez-Ramos et al. | 1994 | Pregnancy | USA | Calcium | Positive angiotensin sensitivity test | Not reported |
| Behjat et al. | 2017 | Pregnancy | Iran | Vitamin D3 | Previous pre-eclampsia | Until 36 weeks’ gestation |
| Karamali et al. | 2015 | Pregnancy | Iran | Vitamin D3 | Uterine artery doppler | From 20 weeks’ to 32 weeks’ gestation |
| Samimi et al. | 2015 | Pregnancy | Iran | Vitamin D3 and calcium | Laboratory tests including free ß-human chorionic gonadotrophin, inhibin α dimeric, unconjugated oestriol and maternal serum α-foetoprotein and haemodynamic assessment of uterine artery Doppler waveform at 16–20 weeks of gestation | From 20 weeks’ to 32 weeks’ gestation |
| Chappell et al. | 1999 | Pregnancy | UK | Vitamin C and vitamin E | Uterine artery doppler and previous pre-eclampsia | From 16–22 weeks’ gestation (depending on prior history of pre-eclampsia) to delivery |
| Poston et al. | 2006 | Pregnancy | UK and Holland | Vitamin C and vitamin E | One or more risk factors for pre-eclampsia (previous pre-eclampsia, delivery <37 weeks, diagnosis of HELLP in previous pregnancy, essential hypertension requiring medication currently or previously, maternal diastolic blood pressure of ≥90 mmHg before 20 weeks’ gestation in the current pregnancy, type 1 or type 2 diabetes requiring insulin or oral hypoglycaemic therapy before the pregnancy, antiphospholipid syndrome, chronic renal disease, multiple pregnancy, abnormal uterine artery doppler waveform, primiparity with BMI at first antenatal appointment of ≥30) | From 14–21 weeks’ gestation to delivery |
| Spinatto et al. | 2007 | Pregnancy | Brazil | Vitamin C and vitamin E | Previous pre-eclampsia in most recent pregnancy that progressed beyond 20 weeks’ gestation | From 12–19 weeks’ gestation to delivery |
| Kalpdev et al. | 2010 | Pregnancy | India | Vitamin C and vitamin E | Essential hypertension | From 16–22 weeks’ gestation to delivery |
| Beazley et al. | 2005 | Pregnancy | USA | Vitamin C and vitamin E | Previous pre-eclampsia, chronic hypertension, insulin-requiring diabetes or multiple gestation | From 14–20 weeks’ gestation |
| Vadillo-Ortega et al. | 2011 | Pregnancy | Mexico | Vitamin C and vitamin E | Previous pre-eclampsia or pre-eclampsia in first-degree relative | From 14–32 weeks’ gestation to delivery |
| Villar et al. | 2009 | Pregnancy | India, Peru, South Africa, Vietnam | Vitamin C and vitamin E | High risk for pre-eclampsia (chronic hypertension, renal disease, pre-eclampsia-eclampsia in the pregnancy preceding the index pregnancy requiring delivery before 37 weeks’ gestation, HELLP syndrome in any previous pregnancy, pregestational diabetes, primiparous with a BMI ≥ 30, history of preterm delivery, abnormal uterine artery Doppler waveforms and women with antiphospholipid syndrome) | 14–22 weeks’ gestation to delivery |
| Zheng et al. | 2020 | Prepregnancy into pregnancy | China | Folic acid | Previous pre-eclampsia | Preconception to delivery |
| Wen et al. | 2018 | Pregnancy | Argentina, Australia, Canada, Jamaica and UK | Folic acid | At least one risk factor for pre-eclampsia (pre-existing hypertension, prepregnancy type 1 or type 2 diabetes, twin pregnancy, previous pre-eclampsia or BMI ≥ 35) | From 8–16 weeks’ gestation to delivery |
| De Araujo et al. | 2020 | Pregnancy | Brazil | Magnesium | ≥1 risk factor for preterm birth or adverse perinatal outcomes in a prior pregnancy (i.e. preterm delivery <37 weeks, still birth at 201/7 weeks, placental abruption, pre-eclampsia or eclampsia, a live-born infant with SGA birthweight <3rd percentile or liveborn infant with birthweight <2500 g) or in current pregnancy (i.e. nulliparity, chronic hypertension, type 1 or 2 diabetes mellitus, maternal age >35 years, pre-pregnancy BMI > 30 or smoking) | From 12–20 weeks’ gestation to delivery |
| Azami et al. | 2017 | Pregnancy | Iran | MMS | At least one risk factor for pre-eclampsia (including chronic vascular disease, hydatidiform mole, multiparity, diabetes mellitus, thyroid disease, chronic hypertension, nulliparity, history of pre-eclampsia, maternal age >35 years, kidney disease, collagen vascular disease, antiphospholipid antibody syndrome, family history of pre-eclampsia, history of thrombophilia and BMI > 25) | From 20 weeks’ gestation to delivery |
| Parrish et al. | 2013 | Pregnancy | US | MMS | Previous pre-eclampsia, prior eclampsia, history of chronic hypertension, diabetes mellitus, connective tissue disease or inherited/acquired thrombophilia | Any time up to 12 weeks’ gestation until delivery |