A Cochrane review [Abstract] 1 included 17 trials involving a total of 9 030 women assessed the effects of advice to increase or reduce energy or protein intake, or of actual energy or protein supplementation or restriction, during pregnancy on energy and protein intakes, gestational weight gain, and the outcome of pregnancy.
In 5 trials (1090 women), nutritional advice to increase energy and protein intakes was successful in achieving those goals and had a lower relative risk of having a preterm birth (RR 0.46, 95% CI 0.21 to 0.98; 2 trials, n=449).
Balanced energy/protein supplementation was studied in 12 trials (n=6705) and was associated with reduced risk of stillbirth (RR 0.62, 95% CI 0.40 to 0.98; 5 trials, n=3408), increased mean birthweight (random-effects MD +40.96 g, 95% CI 4.66 to 77.26; I²=44%, 11 trials, n= 5385). There was also a significant reduction in the risk of small-for-gestational age (RR 0.79, 95% CI 0.69 to 0.90; I²= 6%, 7 trials, n=4408)
In 2 trials (184 women), high-protein supplementation had no significant effect on birthweight.
Clinical comment: The implications for fetal, infant, or maternal health cannot be judged from the available trials. Given the rather modest health benefits demonstrated with actual protein/energy supplementation, however, the provision of such advice is unlikely to be of major importance.
Comment: The quality of evidence is downgraded by study limitations (unclear allocation concealment and blinding, selective reporting).
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