Weight gain during pregnancy is a top concern, not only for how you will look and feel but also because it can be a determining factor in a healthy and happy pregnancy. Being overweight or underweight during pregnancy can both have adverse effects.

How much weight should I gain during pregnancy?

The amount of weight a woman needs to gain during pregnancy is based on her prepregnancy body mass index (BMI), which compares weight to height. In general, if your BMI (Body Mass Index) is low, you should gain more weight than if it's high.

The Institute of Medicine (IOM) recommended weight gain is as follows:

• If you were underweight before pregnancy (for the IOM, that is a BMI of less than 18.5): between about 28 to 40 pounds or 12.5 and 18 kgs extra weight during pregnancy
• If you were normal weight before pregnancy (for the IOM, that is a BMI between 18.5 and 24.9): between about 25 to 35 pounds or 11.5 and 16 kg extra weight during pregnancy
• If you were overweight before pregnancy (for the IOM, that is a BMI between 25 and 29.9): between about 15 to 25 pounds  or 7 and 11.5 kg extra weight during pregnancy
• If you were obese before pregnancy (for the IOM, that is a BMI of over 29.9) about 11 to 20 pounds  or between 5 and 9 kg extra weight during pregnancy
• If you are very young, then more weight gain is probably needed as teenagers may still be growing themselves.

Calculate your BMI here.

Your weight alone is not a good enough indicator in and by itself of how well your baby is doing – or even of your baby’s weight gain. This depends on a lot of factors. It is not really possible to be sure of the baby’s weight before birth. Ultrasound and other tests can give an indication of how the baby is developing.

The above graph shows a graph from a CDC report of weight gain during pregnancy in the U.S. compared to BMI status. Most overweight and obese women gain more weight than recommended.

Gaining too much weight can pose serious health problems for both mothers and their babies.

More than half of American women between ages 25 and 55 are overweight or obese, according to recent data from the Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey. Some women pursue the "perfect bump" by restricting how much they eat, however, many pregnant women are gaining way too much weight, a side effect of the nation's obesity problem. An estimated 40 percent of pregnant women have "super-sized pregnancies," in which they're gaining more than the recommended amount of weight.

Among women who gain more than the recommended amount, several studies have found significantly higher odds of being overweight a year after delivery.

Check out the Pregnancy Weight Gain Calculator!

Health Risks

Gaining too much weight can pose serious health problems for both mothers and their babies. Hefty moms-to-be run the risk of developing gestational diabetes, preeclampsia and having complications during delivery. Babies born to overweight mothers are more likely to be premature or have birth defects. A 2003 study published in the journal Pediatrics found that the babies of obese and overweight women faced greater risks of heart abnormalities or other birth defects like cleft palate.

Although national birth weights for single babies have changed little in the last few decades, according to the American College of Obstetricians and Gynecologists, some doctors say that excessive weight gain during pregnancy is leading to larger babies and an increased number of Caesarean sections. In 2002, C-sections accounted for a record high 26 percent of all births, according to ACOG.

Watch The Ice Cream

Some women who have dieted all their lives may be relieved when they get pregnant, thinking it's finally OK to stop counting calories. But the reality, experts say, is that women need only an additional 100 calories a day during the first trimester and an average of 300 extra calories during the second and third trimesters.

Even though doctors are concerned that women stay within the weight guidelines and not pack it on nor restrict too much, the issue of how to monitor a woman's weight during pregnancy is controversial.

In England, women are weighed only at the beginning and end of the pregnancy, with medical experts citing the lack of evidence that monitoring weight promotes healthier births.

It is inevitable that there will be weight gain during pregnancy. There are general guidelines for proper weight gain during pregnancy and these are used for more than just guiding mom during her prenatal visits. If a pregnant patient were to lose weight or gain a large amount of weight in a short period of time, this could be a sign of a serious health condition or potential risk to the baby.

Average Weight Gain During Pregnancy

On average, the female body is supposed to gain about 25-35 pounds during pregnancy. Women who are underweight should gain a little more and those who are overweight should gain a little less. This weight can be attributed to additional blood volume, the weight of the uterus, placental weight, baby weight, and extra fluid retention during pregnancy.

Women who are pregnant with multiples will not follow the same weight gain path during pregnancy with additional weight being added to the total for the extra babies and extra placentas. A twin pregnancy will mean a weight gain of 35 to 45 pounds. For each additional baby, more weight can be added to that total.

Losing Weight During Pregnancy

Not every woman will gain weight during the first couple of months of pregnancy. This is often due to the more strict food guidelines women fall into once they know they are eating for two instead of one. If every day at lunch, the woman ate at a fast food restaurant and decided to switch that habit out for a salad after finding out about the pregnancy, there is bound to be some sort of weight loss associated with this healthy change.

Overweight or obese pregnant patients can actually inadvertently lose weight for the entire pregnancy and give birth to a healthy baby.

In cases where the mother is not trying to lose weight or has made no real lifestyle changes but continues to lose weight, the obstetrician will run tests to rule out any problems with the pregnancy.

Sudden Weight Gain During Pregnancy

One of the most dangerous pregnancy conditions and complications is preeclampsia. This condition can take the lives of both mother and baby if it is not recognized and treated immediately.

Sudden weight gain during pregnancy is a key sign for preeclampsia. Sudden weight gain is defined as gaining four or more pounds in one week. This weight is often retained water which is another symptom of preeclampsia.

Gestational diabetes can also cause excessive weight gain during pregnancy. This weight gain may not always be on mom but on the baby. Babies born to mothers with gestational diabetes will often gain more weight than babies born to mothers without gestational diabetes. These babies are more often delivered by cesarean section due to their larger size.

Keeping Pregnancy Weight Gain Under Control

There is an old saying that during pregnancy the mom-to-be should eat for two. This is simply not the case. Mom needs to only eat enough for her with the additional protein and calorie amounts suggested by her obstetrician. Literally eating for two will lead to excessive weight gain during pregnancy and could increase the chance of the baby being delivered surgically.

How can I gain extra weight if I am underweight in pregnancy?

There is no hard and fast rule and no specific diet that is proven to be particularly helpful. Researchers have looked at whether diet supplements (such as protein supplements) can help increase weight in under-nourished women. But they have not identified any specific supplement that works well. You can speak with your doctor, midwife, dietitian or nutritionist about how to help increase your weight if you need to.

How can I stop gaining too much weight during pregnancy?

Your baby and you both need a balanced diet during pregnancy. If you limit your energy intake too much, both of you could suffer. On the other hand, too much weight gain could also be unhealthy for you both.

Getting back to roughly where you were before pregnancy is not necessarily going to happen very quickly.

One of the possible problems here, especially if you are already overweight, is that you start eating very different because you are pregnant. You could really enjoy being pregnant and feel like, for these few months, “anything goes.” Or if you are stressed and perhaps struggling a little with all the major changes happening in your body and your life, you could find yourself eating more or differently to make you feel better (often called “emotional eating”). For many women, “emotional eating” can quickly become a way of giving themselves a treat or helping cope with tiredness. A little of that is always fine, but it can quickly develop into a habit that causes problems.

Some of the things that have been tried in research in pregnant women are individual dietary counseling (often with a dietitian or nutritionist), cooking demonstrations and exercise classes. Although these might help individual women, researchers have still not been able to pinpoint anything in particular that has a very high success rate. You can speak with your doctor, midwife, dietitian or nutritionist if you think you might need help, or to find out what options are available in your area.

Is weighing myself regularly a good idea?

This is still not clear. Doctors and midwives will generally weigh you once a month during pregnancy, and they might do this more often if you have signs of problems. Later in the pregnancy, you might have more frequent visits, and you are likely to be weighed then as well.

Weighing yourself could have advantages and disadvantages: researchers are still not sure whether it is helpful. Some research in non-pregnant people has suggested that self-weighing about once a week might help people keep their weight under better control, but this is not certain. Weighing yourself too often could also make you feel worse: we really do not know. At this point, the best that can be said is that weighing yourself up to once a week might not do harm, but there is no reason to stress yourself with frequent weighing.

Does keeping weight gain under control prevent stretch marks and backache?

There is no clear answer to this yet. The AHRQ researchers tried to find out how weight gain affects stretch marks, backache and other common problems for the woman during pregnancy – including whether weight gain affects energy levels. There is, however, surprisingly little research about problems like stretch marks and backache in pregnancy. You will no doubt hear or read many claims about what causes these problems and what might help. These claims are not supported by strong research though.

Whether or not you get stretch marks or a backache does not only depend on the weight you gain. Very sudden and major changes in weight can cause more stretch marks, but whether keeping weight down will prevent stretch marks is just not known.

When can I expect to lose the weight after the birth, and is there anything I should do to help get my weight back to normal?

Getting back to roughly where you were before pregnancy is not necessarily going to happen very quickly. For some women, feeding and taking care of a baby is enough to melt away the weight gained during pregnancy: indeed, they really need this stored up energy to help get through those early weeks and months of motherhood.

Most women will not really get close to their pre-pregnancy weight until perhaps six months after the birth. Women who do not lose most of the weight they gained in pregnancy by six months or a year after the baby is born might be more likely to continue to have weight problems in the long term. The problem might get worse in the next pregnancy, too.

The main options for trying to lose weight are a balanced diet or extra exercise. Programmes to help people change their eating and lifestyle habits are often used to try to achieve this. This does not mean starting immediately after the birth. In the research studies, these kinds of weight control efforts started a month or two after the birth, or even later. After childbirth, weight loss is complicated by the extra nutritional needs of the mother if the baby is breastfed.

Too much, or too sudden, weight loss can also have disadvantages. The possible adverse effects of too much dieting or exercise after having a baby could include a reduction in the quality or quantity of breast milk. But we still do not know for certain when this could become a problem.

Research suggests that light or moderate dieting, with or without exercise, could help you lose weight after childbirth. Exercise might not necessarily help lose weight faster, but it could help increase cardiovascular (heart and circulation) fitness and have other benefits too. You can read more about this research here. Some of the ways that women got rid of the weight in those studies were classes, cooking demonstrations, group support for weight loss and for exercise – groups taking their babies out for walks in prams, for example. You can read more about weight loss generally here.

How do women feel about their bodies and weight during and after pregnancy?

Women are exposed to many unrealistic images of female body size, and body size around pregnancy or after birth is no exception. That makes it difficult for many women to be satisfied with their figure, and it can damage their self-image and enjoyment of their body. The media adds to the pressure on pregnant women and mothers by focusing a lot of attention on how quickly celebrities re-gain their pre-pregnancy figures. However, it is unusual to not gain extra weight in pregnancy — and you cannot really expect to bounce straight back to pre-pregnancy weight within weeks of giving birth.

What’s more, restricting weight gain too much could pose health risks for the growing baby. If you do not gain so much weight that you become overweight or obese, then getting back to normal may not be difficult.

On the other hand, for many women, pregnancy is a time when they really enjoy their babies and curves – and they can feel like it is “time off” from worrying about their size. That can be one of the really enjoyable parts of being pregnant. It could become a problem, though, if you get too far out of your normal weight range and dietary habits: then it might be harder to go back to your “pre-baby” healthier lifestyle. But you do not have to be movie-star thin to have you and your baby be happy and healthy.