Women of reproductive age are bombarded with messages about diet, weight, and body image. There is growing concern on the one hand about an epidemic of obesity, and on the other about a culture that promotes “size zero” as desirable, irrespective of a woman's natural build. Pregnancy is one of the most nutritionally demanding periods of a woman's life, with an adequate supply of nutrients essential to support fetal wellbeing and growth.1 With at least half of all pregnancies unplanned, women need to be aware of the implications of their weight for pregnancy, birth, and the health of their babies. However, the potential to provide women with conflicting information about weight, weight gain, and weight loss extends to pregnancy and birth outcomes.

Over one billion adults in the world are now overweight, with more than 300 million clinically obese.2 In …