Weight Gain During Pregnancy: What to expect?

Last updated

First published

Weight Gain During Pregnancy

It is normal and natural to gain weight during pregnancy. But when you deliver a 7lb baby, you may wonder where the remaining 20 extra pounds are hiding.

Here we will look at how much weight you should gain during pregnancy and what your body needs this weight for.

Your Pre-Pregnancy Weight

What you weighed before you fell pregnant is significant. This is because women who are underweight before conceiving can safely gain more weight during their pregnancy than women who are overweight.

Healthy Weight Before Pregnancy

It is common for women to gain between 22lb and 26lb (10 and 12.5kg) during pregnancy. However, gaining up to 15.5kg is not uncommon.

Underweight Before Pregnancy

Women who weigh less than 50kg (around eight stone) may be given exceptional advice from their midwife to gain additional weight during pregnancy. This is because gaining too little weight can increase the risk of your baby having a low birth weight.

However, some women naturally remain slim during pregnancy and deliver babies of average birth weight.

Overweight Before Pregnancy

Women who weigh over 100kg (15.5 stone) may also receive specialist advice to prevent excess weight gain in pregnancy. You may be advised to avoid gaining more than 6.8kg (15 pounds) to prevent complications, including gestational diabetes, high blood pressure, and pre-eclampsia.

Where Does the Pregnancy Weight Go?

When considering a potential weight gain of 10kg or more, you may wonder where this weight will go.

Some of the weight gained can be attributed to the growing baby. In the UK, the average birth weight of a baby boy is 3.4kg (7lb 8oz), with an average of 3.3kg (7lb 4oz) for a girl.

This still leaves more than 6kg of weight unaccounted for. Other reasons for your increasing importance in pregnancy include the following.

The Placenta

The placenta is the organ that develops inside the uterus to nourish your baby during pregnancy. The umbilical cord inserts into the placenta to carry oxygen and nutrients while removing waste products from the baby. The placenta can weigh around 0.7kg.

Amniotic Fluid

This is the fluid that surrounds the baby in the uterus. It helps the baby's lungs and bones develop properly. The fluid can weigh just under 1kg.


The uterus grows up and out of the pelvis to accommodate the growing baby. By the end of pregnancy, this muscular organ can weigh 1kg.


Your breasts will grow and develop as your body prepares to produce milk to feed your baby. The weight of your breasts can increase by 0.5 to 1.5kg.

Increased Blood Volume

Your circulating blood volume increases, on average, by around 45%. This may lead to an overall weight increase of up to 1.8kg.

Fat Stores

Your body will naturally lay down more fat during pregnancy. This could account for more than 2.5kg of your total weight gain.

Healthy Weight Gain

Women who were healthy before conception will gain weight to support all of the above aspects of pregnancy.

Weight from the placenta, amniotic fluid, and the baby will be lost during delivery. However, the remaining weight of the increased blood volume and enlarged uterus will be lost gradually in the postpartum period. Changes to your breasts depend on factors, including whether you choose to breastfeed.

Burning off the additional fat of pregnancy may take a little longer still.

If you gain more weight than is required during pregnancy, the extra weight will accumulate in your fat stores. This fat will not be automatically lost in the postpartum period and may need an exercise or diet plan to shift.

Therefore, it is wise to monitor your weight gain during pregnancy to ensure that your weight is only increasing by an amount that is healthy for you.

Risks of Excess Weight Gain

Unfortunately, being overweight in pregnancy can increase your risk of certain conditions.

Gestational Diabetes is a form of diabetes that occurs during pregnancy. Diabetes causes high blood sugar levels, leading to premature labor or your baby growing more significantly than usual. Women with a body mass index (BMI) over 30 are at higher risk of this condition.

Pre-eclampsia is a condition that has several causes, one of which is having a BMI over 35. Women with pre-eclampsia have high blood pressure and may need to be monitored as an inpatient during pregnancy. If pre-eclampsia cannot be medically treated, the baby may need to be delivered prematurely.

It is important to note that both of these conditions can affect women who have been previously fit and well. However, to minimize your risk, it is wise to try to gain only a healthy weight during pregnancy.

Final Thoughts

Some weight gain in pregnancy is average. The additional weight is required for various biological functions that support a baby's growth.

However, it is important to monitor your weight gain to ensure it remains healthy for you based on your pre-pregnancy weight.

Healthy pregnancy?

We have the best app for a healthy pregnancy. Track, learn, and enjoy your pregnancy with Bornly.