Multiple pregnancies are associated with higher rates of perinatal mortality and morbidity than singleton pregnancies, mainly due to an increased risk of preterm birth. Because fetal outcome is best at a particular range of maternal weight gain, it has been suggested that women with multiple pregnancies should take special diets (particularly high-calorie diets) designed to boost weight gain. However, 'optimal weight gain' in the mother in retrospective studies may merely reflect good growth of her babies and delivery at or near term (both associated with good outcome) and artificially boosting weight gain by nutritional input may confer no advantage. Indeed, a high-calorie diet may be unpleasant to consume, and could lead to long-term problems of being overweight. It is therefore important to establish if specialised diets are actually of benefit to women with multiple pregnancies and their babies.
Ballard, C. K., Bricker, L., Reed, K., Wood, L., & Neilson, J. P. (2011). Nutritional advice for improving outcomes in multiple pregnancies. In Cochrane Database of Systematic Reviews. John Wiley & Sons, Ltd. https://doi.org/10.1002/14651858.cd008867.pub2