During pregnancy, it is normal, and expected, that you will gain weight. It’s an important part of how your body supports the growth and development of your baby.

Yet for many women, the idea of gaining weight can be confronting, even if it is for a good cause such as nourishing a baby. Not to mention the confusing advice, coming from different sources, about exactly how much weight you should gain.

What Is the Extra Weight?

You are growing another human being in there, so the obvious answer is – baby! By the time your due date arrives, around 30% of your extra body weight isn’t just you – it’s from your baby, the placenta, and the amniotic fluid as well.

While it feels like most of your extra weight is all in your belly, it is actually distributed across your body. Here are some average breakdowns:

An average full term baby weighs 3.3kg
The placenta weighs around 0.7kg
Amniotic fluid surrounding your baby weighs about 0.8kg
Your uterus has grown and weighs an extra 0.9kg
You have 50% more blood volume, weighing an extra 1.2kg
Your breasts have increased in weight by about 0.5kg
Overall, your body is storing about 1.2kg of extra fluid
Fat stores for after birth (to provide energy for breastfeeding) weigh around 4kg.

If you do the calculations, around 60% of the extra weight is the result of your body responding to being pregnant and preparing to nourish your baby after birth.

Weight Gain During Pregnancy

Weighing pregnant women at each antenatal check up is part of standard care in some countries, and in others it usually happens only at your first appointment, or not at all.

The most common reason given for weighing routinely during pregnancy is to make sure women are staying within an optimal weight range.

However, there are differing opinions about what the optimal weight gain in pregnancy actually is. Because women are all different shapes and sizes, what you might gain during pregnancy can depend a lot on your height and health situation, and genetics.

Obviously gaining too much or too little weight can have a negative effect on the growth and development of your baby, as well as potentially causing complications during labour and birth.

Most care providers will weigh you at your first antenatal appointment, to work out your body mass index (BMI). BMI measures your weight in relation to your height, and is used to give an indication of how much weight gain is recommended during pregnancy.

Guidelines for weight gain during pregnancy are based on what your pre-pregnancy BMI is. Most countries use the following guidelines for recommended weight gain in pregnancy:

Underweight: BMI less than 18.5. Weight gain should be 13kg to 18kg (28lb to 40lb)
Normal weight: BMI 18.5 to 24.9. Weight gain should be 11.5kg to 16kg (25lb to 35lb)
Overweight: BMI 25 to 29.9. Weight gain should be 7kg to 11.5kg (15lb to 25lb)
Obese: BMI 30 or more. Weight gain should be 5kg to 9kg (11lb to 20lb)

What If My BMI Is Low?

If you start pregnancy with a low BMI, or lose weight due to excessive morning sickness or hyperemesis gravidum, your care provider will want to keep an eye on your weight gain as your pregnancy progresses. Low BMI can increase the risk of premature labour or a baby with low birth weight.

When thinking about how to eat to gain healthy weight, choose foods that are high in healthy fats, like fish, nuts and avocados. It might help to eat six small meals a day, rather than three larger ones, especially if you are prone to pregnancy nausea.

Try to avoid foods that have empty calories, such as sugary sweets and cakes. A treat won’t hurt, but there is little nutrition in these foods and they won’t help your baby to develop and grow. If you are quite active, try slowing down a little as well. It’s good to continue exercise if you are already active, but make sure you aren’t overdoing it.

What If My BMI Is High?

If you begin with a BMI of 25 or more, it’s important to know that you can still have a healthy pregnancy, and a positive birth. With higher BMI during pregnancy, there are some increased risks of complications, such as:

Gestational diabetes
High blood pressure and preeclampsia
Increased risk of interventions during labour (assisted birth, c-section)
Blood clot in veins
Having a large baby (macrosomia)

While these complications might not occur, care providers will want you to gain weight carefully,to protect your health and that of your baby.

Dieting to lose weight is not recommended during pregnancy; it can be harmful to your baby if essential nutrients are missing from your dietary intake. Eating a balanced diet and getting regular exercise are the best ways to stay healthy.

Avoid foods that are high in sugar and fat, and empty of nutrients. Focus on unprocessed foods, such as fruit and vegetables, lean protein, and healthy fats. If you haven’t exercised for some time, don’t overdo it with a high intensity program. Walking and swimming, or other low impact activities, are your best choice.

Your personal health history and any family history of medical issues need to be taken into account if you have a high BMI. It shouldn’t restrict your birth choices, but often women find the hospital has certain policies on high BMI and birth, such as restricting women from labouring in water, or induction at a certain date. It is a good idea to discuss these limitations with your care provider, as early as possible, so you are aware of how they may affect you.

Should I Be Weighed During Pregnancy?

The important thing to remember is weight gain doesn’t actually give reliable information about your nutrition intake or overall health. Some women can gain normal weight during pregnancy while eating junk food, and others can gain more than what is considered optimal and still be perfectly healthy.

If your care provider routinely does weight checks during pregnancy, and you aren’t comfortable with this, you can decline.

Every woman is unique and many factors play a role in what she weighs at any life stage, including pregnancy. Genetics, age, diet, lifestyle, and metabolism all influence how much weight is gained and lost. The important focus during pregnancy should be nutrition, and the quality of food, rather than quantity.

Remember that pregnancy is a time for weight gain as your body prepares to nourish your baby. It’s an important time to eat well, but you don’t have to ‘eat for two’ as was once believed. In most cases, women will gain the right amount of weight for their body type and needs. Talk to your care provider if you have any concerns about how much weight you are gaining during pregnancy.