If you’re pregnant or trying to conceive, you should be expecting to gain a bit of extra weight in the months of your pregnancy. Weight gain during pregnancy is normal and healthy. You could hardly grow that baby bump (which contains not only your baby but also the placenta which nourishes it and the amniotic fluid which protects it) and bigger pregnancy breasts without adding a few extra kilos!
However, pregnancy is not a time when you need to give up on your exercise routine, eat for two, or eat whatever you want. Although some extra weight is normal and healthy, too much weight gain during pregnancy can be detrimental to both you and your baby.
So how much weight should you gain as you go about growing your baby? It depends on how much you weighed at the time you conceived your baby.
Measuring and monitoring weight gain during pregnancy
Before pregnancy a woman’s weight is measured in kilograms and a Body Mass Index (BMI) calculated. The BMI is your weight in kilograms divided by your height squared (or multiplied by itself) in m2.
A woman’s pre-pregnancy BMI determines how much weight she should gain during pregnancy.
Healthy pregnancy weight gain
A healthy weight woman should gain 11.5-16kg during pregnancy (see Table 1). However if you’re underweight you’ll need to try and gain a few extra kilograms, while if you’re overweight or obese you’ll need to gain few less (although you should never attempt to lose weight while you’re pregnant). If you’re carrying twins or triplets you should gain more weight to account for the extra babies.
Table 1: Healthy weight gain during pregnancy and pre-pregnancy BMI
|Pre-pregnancy BMI||Category||Recommended Weight Gain|
|BMI < 18.5||Underweight||12.5 – 18.0kg|
|BMI 18.5 – <25.0||Healthy weight||11.5 – 16.0kg|
|BMI 25.0 – <30.0||Overweight||7.0 – 11.5kg|
|BMI ≥30.0||Obese||5.0 – 9.0kg|
When does pregnancy weight gain occur?
The majority of weight gain occurs in the second and third trimesters of pregnancy. In the first trimester you should only gain a kilogram or two. By pregnancy week 20 you should have put on about 3kg. Weight gain occurs most rapidly in weeks 21-36 of pregnancy, when you should expect to gain about half a kilogram per week. In the final weeks of your pregnancy, your rate of weight gain slows down again.
Pregnancy weight gain in Australia
In Australia the majority of women gain either too much or not enough weight during pregnancy. About a quarter of women do not gain enough weight and increase their risk of pregnancy complications such as preterm delivery. 38% of all pregnant women in Australia gain too much weight during pregnancy increasing their baby’s risk of chronic health conditions later in life. Amongst women who are overweight when they become pregnant, more than half gain excessive weight during pregnancy.
Many women who gain too much weight during pregnancy fail to lose the weight after childbirth.
How much extra weight is healthy?
If you begin your pregnancy at a healthy weight (BMI 18.5-24.99) gaining 11.5-16kg during pregnancy is normal and healthy. If you’re underweight you should gain at least 12 kg and up to 18kg. You should never attempt to lose weight while you’re pregnant, however if you are overweight or obese, you should restrict how much weight you gain.
- National Health and Medical Research Council. Clinical Management Guidelines for the management of overweight and obesity in adults, adolescents and children in Australia. 2013. (cited 14 April 2014). Available from: (URL Link)
- Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Management of Obesity in Pregnancy- C-Obs 49. 2013. (cited 1 May 2014). Available from: (URL Link)
- Mayo Clinic. Pregnancy Weight Gain. 2014. (cited 1 May 2014). Available from: (URL Link)
- Academy for Educational Development. Maternal nutrition during pregnancy and lactation. 2004. [cited 1 May 2014]. Available from: [URL Link]