Weight gain during pregnancy

What is Normal?

Gaining weight during pregnancy is to be expected, but often the question of how much can be confusing. Firstly pregnancy is not the time to try to lose weight, or embark on any dieting regime, as restrictions may affect the development of the unborn baby. However, it is important to know that the amount of weight you gain can not only affect your health but also the health of your growing baby.

Benefits of being at an healthy pre-pregnancy weight include:Pregnant lady on scales

  • Decreased risk of diabetes during pregnancy
  • Decreased risk of high blood pressure during pregnancy

The advantages of being in the healthy weight range don’t stop at birth. Babies of mothers with healthy BMIs are more likely to be healthier as they grow and less likely to suffer obesity/diabetes as children and as adults.

Recommended Pregnancy Weight Gain

The recommended weight gain during pregnancy depends on your weight and Body Mass Index (BMI) before becoming pregnant. This is outlined in the table below.

Essentially if you are in the underweight category before becoming pregnant, you will need to gain more weight throughout pregnancy than if you are in the overweight or obese category.

If you are overweight it is important not to diet or skip meals as this may harm the baby. If you are concerned about your weight it is important to talk with your doctor who may refer you to a Dietitian.

Effects of too much weight gain during pregnancy

  • Increased risk of developing high blood pressure, gestational diabetes or requiring a Caesarean section.
  • More difficult to lose the weight after pregnancy, as the demands of a new baby can make participating in regular physical activity and eating healthy a challenge.
  • Carrying excess weight can impact future pregnancies and fertility.

Weight gain from 20 weeks

Steady weight gain during pregnancy is important for mother and baby as it helps to avoid adverse effects on specific foetal organ systems during critical periods (e.g. kidney development 28–30 weeks). The table suggests average rate of weight gain from the 2nd and 3rd trimester.

Table – Expected total weight gain and rate of weight gain based on BMI 

Pre-Pregnancy BMI Category

Total Weight Gain (Kg)

One baby pregnancy

Average rates of WEEKLY weight gain in 2nd and 3rd Trimester


(BMI less than 18.5)

12.5 to 18kg


(0.44- 0.58)

Healthy weight

(BMI 18.5 to 24.9)

11.5 to 16kg


(0.35- 0.50)


(BMI 25 to 29.9)

7 to 11.5kg




(BMI greater than 30)

5 to 9kg



If you don’t know your BMI or are unsure how to calculate it, follow the link to a BMI calculator.


  • The above-recommended ranges are suggested to be used in combination with a clinical assessment with health care provider (GP, obstetrician, dietician) and as a guide only.
  • The calculations for rate of weight gain assume a 0.5-2kg gain only during the first trimester

Table Reproduced: Management of Obesity in Pregnancy, Institute of Medicine weight gain during pregnancy suggested guidelines, 2013, The Royal Australian and New Zealand College of Obstetricians and Gynaecologists.