It depends on your weight before you become pregnant.
Weight gain in pregnancy varies greatly. Most pregnant women gain between 10kg and 12.5kg (22-28lb), putting most of the weight on after week 20.
Much of the extra weight is due to your baby growing, but your body will also be storing fat, ready to make breast milk after your baby’s born.
Putting on too much or too little weight can lead to health problems for you or your unborn baby.
Gaining too much weight
Putting on too much weight can affect your health and increase your blood pressure. However, pregnancy is not the time to go on a diet. It’s important you eat healthily.
Gaining too much weight can increase your risk of complications. For example:
- Too much glucose (sugar) in your blood during pregnancy can cause gestational diabetes. This increases your risk of having a large baby, which may mean your labour could be induced or you could have a caesarean section. Your baby may have health problems shortly after birth, such as heart and breathing problems. They may also be at risk of obesity or diabetes later in life. Gestational diabetes also increases the risk of stillbirth.
- A rise in blood pressure can be the first sign of pre-eclampsia. Although most cases are mild and cause no trouble, pre-eclampsia can be serious. It can cause fits in the mother (called eclampsia) and affect the baby’s growth. Pre-eclampsia usually happens towards the end of pregnancy but it may happen earlier. It can also happen after the birth. Occasionally, it’s necessary to deliver the baby early by inducing labour or a caesarean section.
Gaining too little weight
Gaining too little weight can cause problems such as early (premature) birth and a baby with a low birth weight (less than 2500g or 5½ lbs at birth). It can also mean that your body is not storing enough fat.
Lack of weight gain can be related to your diet and weight before you become pregnant.
Not putting on enough weight can also be caused by your body not absorbing food properly, for example, if you have an eating disorder, such as anorexia nervosa or bulimia. This can increase your risk of anaemia.
However, some naturally slim women stay slim while they’re pregnant and have healthy babies.
Try to stay active by keeping up your normal daily activity or exercise (unless you’ve been advised by your midwife or GP not to exercise).
Staying active is important while you’re pregnant as it will help prepare your body for labour and birth.
Advice about your weight
Your midwife or GP may have special advice for you if you weigh:
- more than 100kg (15½ stone)
- less than 50kg (8 stone)
If you’re concerned about your weight or any other aspect of your health when you’re pregnant, ask your midwife or GP for advice.
Last Updated: 05 December 2011