Why weight matters in pregnancy

Weight gain in pregnancy varies greatly. Most pregnant women gain between 10kg and 12.5kg (22lb to 26lb), putting on most of the weight 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 is born.

Putting on too much or too little weight can lead to health problems for you or your unborn baby.

Putting on too much weight can affect your health and increase your blood pressure. But pregnancy isn't the time to go on a diet, as it may harm the health of the unborn child. It's important that you eat healthily.

Gaining too much weight can increase your risk of complications. These include:

  • gestational diabetes: too much glucose (sugar) in your blood during pregnancy can cause gestational diabetes, which increases your risk of having a large baby
  • pre-eclampsia: a rise in blood pressure can be the first sign of pre-eclampsia; although most cases are mild and cause no trouble, it can be serious

Gaining too little weight may cause problems such as premature birth and a baby with a low birth weight (less than 2.5kg or 5.5lb at birth). It may also mean your body isn't storing enough fat. Lack of weight gain maybe related to your diet and weight before you become pregnant. But some naturally slim women stay slim while they're pregnant and have healthy babies.

Staying active is important while you're pregnant, as it'll prepare your body for labour and birth. Keep up your normal daily activity or exercise, unless you have been advised by your midwife or GP not to exercise.

If you're concerned about your weight or any other aspect of your health while pregnant, ask your midwife, obstetrician or GP for advice.

Improving the physical and emotional health and wellbeing of expectant mothers, infants, children and young people throughout Aneurin Bevan University Health Board Area.

(N.B: The Family and Therapies team at ABUHB is NOT responsible for the content on the webpage links that we refer to in our resource sections and linked information to external sites. All information was accurate and appropriate at the time the webpage was created.)

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