Weight gain in pregnancy

The U.S. Institute of Medicine (IOM) issues guidelines that are followed by doctors around the world. They recommend how much weight should be gained during pregnancy as follows:

• For women who are underweight before pregnancy (body mass index ( BMI) of less than 18.5): between 12.5 and 18 kilograms
• For women who are of normal weight before pregnancy ( BMI of between 18.5 and 24.9): between 11.5 and 16 kilograms
• For women who are overweight before pregnancy ( BMI of between 25 and 29.9): between 7 and 11.5 kilograms
• For women who are obese before pregnancy ( BMI greater than 30): between 5 and 9 kilograms

A pregnant woman’s weight alone is not a good indicator of how well the baby is doing – and not even of how her baby is growing. That depends on a lot of factors. It is hard to predict during the pregnancy how much the baby will weigh at the end of pregnancy. Ultrasound scans and other tests can only give us a rough idea of how the baby is developing and how much he or she might weigh at birth.

Women who gain a lot of weight in pregnancy have a higher risk of certain health problems and complications during childbirth. For instance, they are more likely to have a big child with a birth weight of over 4,000 g or 4,500 g (macrosomia), and are more likely to need a Cesarean section. The risk of a preterm birth is also higher.

Complications are more common in women who were very overweight before the pregnancy. They are also more likely to have difficulties losing the extra weight after giving birth.

On the other hand, if a woman doesn't gain enough weight and doesn’t get enough different foods in pregnancy, it can harm her growing baby: babies are then often born too early (preterm birth) or often weigh too little at birth.

If a woman puts on weight suddenly, or if she generally gains more than half a kilogram per week, her weight will be monitored by a doctor or midwife. Additional tests and examinations might be needed too.

Very fast and extreme weight gain (such as 1 kilogram within a week) is typically due to changes in water retention and can be a sign of health problems such as pre-eclampsia. The main symptom of this pregnancy-related condition is high blood pressure, sometimes accompanied by nausea, headaches and dizziness too. Pre-eclampsia can be life-threatening for both the mother and her child, and it needs to be treated by a doctor as soon as possible.

Putting on a lot of weight in pregnancy can increase the risk of women developing diabetes in pregnancy (“gestational diabetes”) – or it can be a sign that they have developed it. Gestational diabetes is where blood sugar levels change in women who didn't have diabetes before becoming pregnant. Gestational diabetes increases the risk of pre-eclampsia, and can result in the unborn baby putting on a lot of weight. If the baby is very big and heavy, complications during childbirth are more common.

Keeping your weight in check during pregnancy lowers the risk of gestational diabetes and of the child being very large and heavy during childbirth.

This is best achieved by watching your diet and getting regular exercise. Even doing one of these things can make a difference. And doing both makes it easier to lose weight again after childbirth. This has been shown by studies that looked into programs to support women in changing their diet and exercising. The studies didn’t show that this will lower the risk of complications during childbirth or prevent the need for a Cesarean section, though.

These things are most effective if you have gestational diabetes. Changes to your diet and more exercise can lower your blood sugar levels and control weight gain. That can also lower the risk of complications during childbirth.

Because carbohydrates increase blood sugar levels, women who are very overweight or have gestational diabetes are usually advised to cut down on carbohydrates (“carbs”) while making sure that they still get enough fiber, and to generally eat a balanced diet otherwise. Other common advice includes eating three not-too-big main meals and two to three smaller meals per day.

The exact dietary changes to be made will depend on things like how much you weighs, what sort of diet you have been eating so far, and how much exercise you get. Advice from a nutritional therapist can help to avoid adverse effects. Pregnant women need to make sure that they get enough calories and important nutrients, which is why they shouldn’t go on a low-calorie diet, for instance.

Doing at least 30 minutes of a strenuous physical activity on about three to four days per week is often enough. Suitable types of exercise include swimming, cycling and brisk walking. Women with a greater risk of preterm birth are usually advised to avoid sports altogether. When in doubt, don't hesitate to ask your gynecologist or midwife.

If a woman who is underweight becomes pregnant and finds it difficult to put on weight, she can seek advice from her doctor or midwife. Studies suggest that professional dietary advice can help women gain weight and lower the risk of giving birth too early (preterm birth).

Protein supplements have been found to help some underweight women increase their weight. This lowers the risk of their child being born underweight, as well as reducing the risk of having a miscarriage. However, very protein-rich dietary supplements with a protein content of more than 25% don't appear to help. Research also suggests that these very high-protein products might limit the growth of the baby. So it's important to make sure you get a balanced mix of nutrients. “More” is not “better” in this case.

Stretch marks are caused by overextending the connective tissue. Although there are many claims about what might help, none of them have been confirmed in good-quality research.

Whether or not you get stretch marks not only depends on how much weight you gain in total. Factors like how fast you gain weight can make a difference too. For instance, gaining a lot of weight very suddenly can cause more stretch marks than gaining weight gradually. But it's not clear whether stretch marks can be prevented by keeping your weight down.

Many mothers find that it takes a while before they reach their pre-pregnancy weight again. For some women, breastfeeding and taking care of a baby are enough to melt away the weight gained during pregnancy: It's as though they really need this stored up energy to help get through the first few weeks and months of motherhood.

But most women won't really get close to their pre-pregnancy weight until perhaps six months after giving birth. Women who don't lose weight, or even gain weight instead, might have a higher risk of health problems. These problems could get worse in other pregnancies.

The best way to lose weight is by combining a change in diet with extra physical exercise. Exercise alone probably won't do much. Programs designed to help people change their eating and lifestyle habits are often used to try to lose weight. In the research on these programs, women started weight control efforts a month or two after giving birth, and sometimes later. Immediately after birth, mothers need enough nutrients to breastfeed their child, so it’s not a good time for them to try to lose weight.

Too much, or too sudden, weight loss can have disadvantages too. For instance, if you go on a diet that is too strict or too one-sided after having a baby, it could reduce the quantity of your breast milk or the nutrients it contains.

Women are constantly confronted with idealized standards of beauty. The media also often show images of idealized pregnant women. This makes it difficult for many women to be happy with their figure, and it can damage their self-image and enjoyment of their body. The media add to the pressure on pregnant women and mothers by focusing a lot of attention on how quickly celebrities return to their pre-pregnancy figures after giving birth. But women need to gain weight during pregnancy – and they can't expect to lose it all again within a few weeks after giving birth.

A lot of women see pregnancy as a time to enjoy their belly, curves and the baby growing inside their body – and allow themselves some “time off” from worrying about their size.