Why will I gain weight during pregnancy?

It's normal to gain weight during pregnancy. You need more nutrients from your diet when you are pregnant, especially as you get further along in pregnancy. This gives your body the extra energy it needs as your baby grows.

Gaining too much weight can increase the risk of problems such as:

• Having a baby that is larger than normal

• Needing to have a cesarean birth (c-section)

• High blood pressure or diabetes during pregnancy

Gaining too little weight can also cause problems, especially if you were underweight before pregnancy. These include premature, or "preterm," birth or having a baby that is smaller than normal.

Where does weight gain during pregnancy come from?

It comes from different places, including:

• The fetus (developing baby)

• Increased fat, blood, and fluid in your body

• The fluid surrounding the fetus

• Your breasts getting bigger

• Your uterus growing

• The placenta (the organ that attaches the baby to the uterus)

Most weight gain happens during the second and third trimesters of pregnancy. During this time, you should be gaining weight at a steady rate.

How much weight should I gain?

It depends on how much you weighed before pregnancy.

Doctors use a number called body mass index, or "BMI," to help understand a person's health. Your BMI is based on your height and weight.

Experts recommend different amounts of weight gain based on your BMI before pregnancy. In general:

• BMI before pregnancy under 18.5 – Gain between 28 and 40 pounds (12.5 to 18 kg) during pregnancy.

• BMI before pregnancy between 18.5 and 24.9 – Gain between 25 and 35 pounds (11.5 to 16 kg) during pregnancy.

• BMI before pregnancy between 25 and 29.9 – Gain between 15 and 25 pounds (7 to 11.5 kg) during pregnancy.

• BMI before pregnancy 30 or greater – Gain between 11 and 20 pounds (5 to 9 kg) during pregnancy. Some experts suggest gaining no more than about 11 pounds (5 kg).

If you are pregnant with multiple babies, such as twins or triplets, you will need to gain more than these recommended amounts.

How can I keep a healthy weight during pregnancy?

Your doctor, nurse, or midwife will check your weight at each visit. If you are gaining more or less weight than expected, they will talk to you about it and whether you should make any changes.

To keep a healthy weight, try to:

• Eat a balanced diet with lots of fruits, vegetables, whole grains, and protein. It might help to work with a dietitian (nutrition expert). Your doctor might recommend this if your BMI was lower or higher than normal before pregnancy, or if you follow a restricted diet. A dietitian can help make sure you get the right nutrients for your body and your baby. They can also recommend specific foods to include in your diet.

• Get regular physical activity. Your doctor, nurse, or midwife can talk to you about what types of exercise are safe during pregnancy.

Eating healthy foods and moving your body have many other health benefits besides helping manage your weight.

If you start to lose weight, tell your doctor or nurse. For people with a very high BMI who lose weight through lifestyle changes, this is not always a problem. But if you are losing weight for another reason, like from severe morning sickness, you might need treatment.