Table 1

Summary of results from systematic reviews of randomised controlled studies

ReviewNumber studies/individualsEffect size (CI) risk ratio, random effectsHeterogeneity (I2)Significance (p value)*Level of evidence (GRADE)
Preterm birth
 Bi2711/38220.98 (0.77 to 1.26)33%− (NR)Moderate
 De-Regil/Palacios23 24 3/4770.36 (0.14 to 0.93)10%+ (0.035)Very low
 Perez-Lopez31 3/3841.24 (0.59 to 2.61)0%− (0.56)Very low
 Roth 28 14/3757 1.00 (0.77 to 1.30) 0% − (0.677) High
 Zhou266/16870.61 (0.34 to 1.07)26%− (0.09)Low
Pre-eclampsia
 De-Regil/Palaciosis23 24 2/2190.52 (0.25 to 1.05)0%− (0.069)Very low
 Khaing33 3/3570.47 (0.24 to 0.89)0%+ (0.02)Very low
 Newberry32 1/504NR; by group for individual studyNR+ (n=1) Very low
 Perez-Lopez31 3/ 654 0.91 (0.45 to 1.86) 24% − (0.80) Low
 Roth 28 3/7061.09 (0.43 to 2.76)66%− (0.047)Very low
Gestational diabetes
 De-Regil/Palacios23 24 2/2190.43 (0.05 to 3.45)0%− (0.43)Very low
 Perez-Lopez31 3/3841.05 (0.60 to 1.85)0%− (0.86)Very low
 Roth 28 5/10300.65 (0.39 to 1.08)45%− (0.125)Very low
Small for gestational age
 Bi27 6/ 1002 0.72 (0.52 to 0.99) 0% + (0.04) Low
 Harvey14 2/245NR; by individual studyNR− (n=2) Very low
 Perez-Lopez31 3/4560.77 (0.46 to 1.30)15%− (0.33)Very low
 Roth 28 5/7410.60 (0.40 to 0.90)0%+ (0.704)Very low
Low birth weight
 Bi274/7750.52 (0.20 to 1.37)65%− (NR)Very low
 De-Regil/Palacios23 24 3/4930.4 (0.24 to 0.67)4%+ (0.00048)Very low
 Perez-Lopez31 4/4960.72 (0.45 to 1.17)0%− (0.19)Very low
 Roth 28 7/1156 0.74 (0.47 to 1.16) 47.3% − (0.077) Low
Stillbirth
 De-Regil/Palacios23 24 3/5400.35 (0.06 to 1.99)0%− (0.23)Low
 Roth 28 16/4606 0.75 (0.50 to 1.12) 0% − (0.858) High
Caesarean section
 De-Regil/Palaciosis23 24 2/3120.95 (0.69 to 1.31)12%− (0.75)Low
 Perez-Lopez31 4/10280.97 (0.81 to 1.32)0%− (0.75)Low
 Roth28 16/3240 1.02 (0.93 to 1.12) 0% − (0.701) High
  • *Significance indicated as positive (+) when p value≤.05 and negative (−) if >0.05.

  • †For each outcome, the review with the highest level of evidence is presented in bold font.

  • ‡In absence of pooled data, this indicates the number of studies with positive or negative statistical significance.