Weight gain in pregnancy is a worry for the majority of women. We know from Swedish registry data that women who start off pregnancy in the normal weight range tend to get back to that weight within 6 months of delivery, no matter how much weight they put on.

Women who start off pregnancy either overweight or obese will tend to struggle to get to their pre-pregnancy weight. These women will tend to put on weight after each pregnancy.

Women come in all shapes and sizes, and it is their genetic make-up and metabolism that will determine what is a normal weight gain in pregnancy.

The Body Mass Index (BMI) is a measure of weight versus height that is suitable for use by most women.

weight in pregnancy

In general, the risks of pregnancy start to increase at a BMI of 28 kg/m2. For an average size woman, this is at about 80kg. Risks rise exponentially with weight and are unacceptable beyond a BMI of 35 kg/m2 or about 100kg.

Risks of pregnancy that are increased in overweight and obesity women include:

  • Thromboembolism – development of clots in the legs (DVT), lungs (pulmonary embolus) and brain (stroke)
  • Gestational diabetes – this normally resolves after pregnancy but women have a lifetime risk of 50% of developing type 2 diabetes mellitus
  • Gestational hypertension – again this usually resolves but women are at risk of developing high blood pressure after pregnancy
  • Pre-eclampsia – this is a severe blood pressure problem in pregnancy that can affect multiple organs in the woman and also affect the unborn baby. Babies often need early delivery with risks due to prematurity and women can develop multiple organ failure.
  • Infections and their complications – involving the womb and pelvis, Caesarean wound, chest and urine
  • Overdue pregnancy and need for induction of labour