Weight gain during pregnancy
IOM guidelines, BMI categories and healthy development
The recommended weight gain during pregnancy depends decisively on the pre-pregnancy BMI. The Institute of Medicine (IOM) established guidelines in 2009 based on extensive research data, which have since served as the reference worldwide – including in Germany. For women with normal weight (BMI 18.5–24.9), the IOM recommends a total weight gain of 11.5–16 kg. At a pre-pregnancy BMI of 22 (normal weight), the recommendation is identical.
Weight gain is not distributed evenly across the 40 weeks of pregnancy. In the first trimester (weeks 1–12), most women gain only 0.5–2 kg. In the second and third trimesters, the gain increases to 350–500 g per week (normal weight). This distribution reflects the baby’s growth: in the first trimester the baby grows slowly, in the second the growth accelerates, and in the third the weekly gains are highest. Regular weight checks at prenatal appointments accompany this process.
Women with overweight or obesity benefit from lower weight gains (7–11.5 kg or 5–9 kg respectively), since a higher pre-pregnancy weight increases the risk of pregnancy complications such as gestational diabetes and preeclampsia. These women have sufficient body fat reserves to nourish the baby without gaining much weight. Still, zero gain or weight loss during pregnancy is not recommended.