What do systematic reviews say?

Vitamin D vs placebo or no intervention

Vitamin D supplementation probably leads to lower pre‐eclampsia compared with placebo or no intervention (moderate certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.48 [0.3, 0.79]
  4 studies · 499 participants
  Moderate

Vitamin D + calcium + other vitamins and minerals vs calcium + other vitamins and minerals (but no vitamin D)

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  no estimate extracted
  0 studies · 0 participants
  GRADE not reported

Vitamin D plus calcium vs placebo or no intervention

Vitamin D + calcium supplementation probably leads to lower pre‐eclampsia compared with placebo or no intervention (moderate certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.5 [0.32, 0.78]
  4 studies · 1174 participants
  Moderate

Continuous glucose monitoring system vs intermittent glucose monitoring

Continuous glucose monitoring may leads to lower hypertensive disorders of pregnancy (including pre‐eclampsia,… compared with intermittent glucose monitoring (low certainty).

• Techniques of monitoring blood glucose during pregnancy for women with pre‐existing diabetes 2019 · Cochrane Headline outcomes only
  RR 0.58 [0.39, 0.85]
  2 studies · 384 participants
  Low

Automated telemedicine monitoring vs conventional

• Techniques of monitoring blood glucose during pregnancy for women with pre‐existing diabetes 2019 · Cochrane Headline outcomes only
  no estimate extracted
  0 studies · 0 participants
  GRADE not reported

Constant CGM vs Intermittent CGM

• Techniques of monitoring blood glucose during pregnancy for women with pre‐existing diabetes 2019 · Cochrane Headline outcomes only
  no estimate extracted
  0 studies · 0 participants
  GRADE not reported

Self‐monitoring vs a different type of self‐monitoring

• Techniques of monitoring blood glucose during pregnancy for women with pre‐existing diabetes 2019 · Cochrane Headline outcomes only
  no estimate extracted
  0 studies · 0 participants
  GRADE not reported

Self‐monitoring at home vs hospitalisation

It is very uncertain whether self‐monitoring at home changes hypertensive disorders of pregnancy (including pre‐eclampsia,… compared with hospitalisation (very low certainty).

• Techniques of monitoring blood glucose during pregnancy for women with pre‐existing diabetes 2019 · Cochrane Headline outcomes only
  RR 1.19 [0.41, 3.51]
  1 study · 100 participants
  Very low

Calcium supplementation/fortification vs placebo (outcomes

Calcium supplementation showed no clear difference in pre‐eclampsia compared with placebo (maternal outcomes) commencing before or early (low certainty).

• Calcium supplementation commencing before or early in pregnancy, for preventing hypertensive disorders of pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.8 [0.61, 1.06]
  1 study · 579 participants
  Low

Calcium supplementation/fortification vs placebo (outcomes

Calcium supplementation showed no clear difference in pre‐eclampsia, or pregnancy loss, or stillbirth (or combination) at… compared with placebo (maternal outcomes) commencing before or early (low certainty).

• Calcium supplementation commencing before or early in pregnancy, for preventing hypertensive disorders of pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.82 [0.66, 1]
  1 study · 633 participants
  Low

Guided imagery vs quiet rest

The review found no eligible studies for this question.

• Guided imagery for treating hypertension in pregnancy 2019 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

A dose of vitamin D 601 IU or higher vs 600 IU or lower alone or with other nutrients

A dose of vitamin D 601 IU or higher showed no clear difference in pre‐eclampsia compared with 600 IU or lower alone or with other nutrients (low certainty).

• Regimens of vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.96 [0.65, 1.42]
  5 studies · 1553 participants
  Low

A dose of vitamin D 4000 IU/d or more vs 3999 IU/d or less alone or with any other nutrient

A dose of vitamin D 4000 IU/d or more showed no clear difference in pre‐eclampsia compared with 3999 IU/d or less alone or with any other nutrient (low certainty).

• Regimens of vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.87 [0.62, 1.22]
  4 studies · 1903 participants
  Low

Intervention not reported

The intervention may leads to lower pre‐eclampsia (low certainty).

• Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems 2018 · Cochrane Headline outcomes only
  RR 0.45 [0.31, 0.65]
  13 studies · 15730 participants
  Low

Any antihypertensive drug vs no antihypertensive drugs/placebo

It is very uncertain whether any antihypertensive drug changes severe pre‐eclampsia compared with no antihypertensive drugs/placebo (very low certainty).

• Antihypertensive drug therapy for mild to moderate hypertension during pregnancy 2018 · Cochrane Headline outcomes only
  RR 0.56 [0.15, 2.02]
  3 studies · 416 participants
  Very low

Any antihypertensive drug vs no antihypertensive drugs/placebo

Any antihypertensive drug showed no clear difference in proteinuria/pre‐eclampsia compared with no antihypertensive drugs/placebo (low certainty).

• Antihypertensive drug therapy for mild to moderate hypertension during pregnancy 2018 · Cochrane Headline outcomes only
  RR 0.92 [0.75, 1.14]
  23 studies · 2851 participants
  Low

Intervention not reported

The intervention showed no clear difference in pre‐eclampsia (low certainty).

• Omega‐3 fatty acid addition during pregnancy 2018 · Cochrane Headline outcomes only
  RR 0.84 [0.69, 1.01]
  20 studies · 8306 participants
  Low

Metformin vs placebo

Metformin showed no clear difference in pre‐eclampsia compared with placebo (low certainty).

• Metformin for women who are overweight or obese during pregnancy for improving maternal and infant outcomes 2018 · Cochrane Headline outcomes only
  RR 0.74 [0.09, 6.28]
  2 studies · 840 participants
  Low

Dietary advice vs standard‐of‐care therapy

Dietary advice interventions showed no clear difference in hypertensive disorders of pregnancy (pre‐eclampsia) compared with standard care (maternal outcomes) (low certainty).

• Dietary advice interventions in pregnancy for preventing gestational diabetes mellitus 2017 · Cochrane Headline outcomes only
  RR 0.61 [0.25, 1.46]
  2 studies · 282 participants
  Low

Adverse event outcomes for dietary combined with physical activity interventions vs standard‐of‐care therapy

Combined diet and exercise interventions showed no clear difference in hypertensive disorders of pregnancy (pre‐eclampsia) compared with standard care (mother) (low certainty).

• Combined diet and exercise interventions for preventing gestational diabetes mellitus 2017 · Cochrane Headline outcomes only
  RR 0.98 [0.79, 1.22]
  8 studies · 5366 participants
  Low