This post discusses the Cochrane Systematic Review “Antenatal dietary advice and supplementation to increase energy and protein intake”
Let us understand the terms involved:
Antenatal: A medical term to describe the time between conception and delivery i.e. pregnancy (Gestation also refers to pregnancy, hence the disambiguation).
Antenatal dietary advice: Dietary advice given during pregnancy
Isocaloric protein supplementation: Balanced supplements in which the protein replaces equal portions of other nutrients (fats, carbohydrates, etc.)
Small-for-gestational-age baby: A baby that is physically smaller in size than what is normally expected at that time (during pregnancy or at birth).
What were the (research) questions the reviewers were trying to answer? What are the effects of dietary advice to increase protein and energy intake during pregnancy? What are the effects of actually supplementing energy and protein on their intake during pregnancy? What are the effects on the mother and child of these interventions?
What did the reviewers do? They included Randomized Controlled Trials (RCTs) in which women were either advised to increase protein and energy intake, or provided protein and energy supplementation during pregnancy. They identified 46 trials, but found only 15 trials (involving 7410 women) suitable for inclusion. The rest of the procedure was similar to that described in an earlier post.
What did they find?
1. Providing dietary advice resulted in an increase in the mother’s protein intake, and reduced the chances of preterm delivery in two trials involving 449 women. One study found an increase in the head circumference of babies at birth.
2. Giving balanced energy and protein supplements to pregnant women resulted in a definite increase in average weight at birth (11 trials, 5385 women) with fewer stillbirths (five trials, 3408 women), and fewer small-for-gestational-age births (seven trials, 4408 women).
3. High-protein supplementation showed no benefit for women and potential harm for the baby.
4. Isocaloric protein supplementation showed no benefit for women or their babies.
How does one explain these findings?
The following points are in order:
1. The review was restricted to RCTs. Evidence from observational studies might be different.
2. The quality of evidence was low/ poor for many important outcomes. In addition, there was unclear or high risk of bias in many studies. Therefore, the results must be interpreted with caution.
Bottomline: Dietary advice/ balanced protein supplementation to women during pregnancy might be beneficial. High-protein supplementation might be harmful to the baby, and does not benefit the mother. Isocaloric protein supplementation does not seem to benefit mothers or their babies.