Average Weight Gain During Pregnancy: BMI & Weight Change Factors

average weight gain during pregnancy. woman holding scales

Not every future mother understands how important it is to keep the reasonable boundaries in the issue of nutrition. Some women are worried about the body that will be difficult to get back in shape after childbirth, and begin to limit themselves in everything. Other women believe that now they need to eat literally “for two” and heavily lean on their favorite foods. In fact, any deviation from the average weight gain during pregnancy can equally carry a danger to the health of the woman and her baby. So, what should a future mom know about changes in body weight during pregnancy? And how to calculate the optimal weight gain? Find out answers to these and more questions in the article.

Why Is Insufficient or Excess Weight During Pregnancy Dangerous?

The average weight gain during pregnancy is between 9 and 14 kg. Of course, this cannot be applied to every particular case, since the exact figure depends on many factors. Still, a sharp deviation from it in one or the other direction should alert the future mother.

Insufficient weight often occurs in pregnant women in the first months. It is explained by the fact that during this period women usually suffer from toxicosis. If it is not accompanied by severe vomiting (after each meal), the baby is most likely out of danger.

The greatest risk is low weight in the second-third trimesters. At this time, the fetus is in great need of nutrients. Their deficiency can lead to a deficit in the weight of the newborn, various pathologies in development and psychological problems. The level of important hormones in the woman’s body can decrease in this case. This is fraught with miscarriage or premature birth.

Excess Weight

At the same time, excess weight is not only an aesthetic problem of pregnancy. Often it provokes the development of gestosis. It is a dangerous condition called late toxicosis. Gestosis carries a direct threat to the health of the child, as it can cause placental detachment and other troubles.

Excess weight is even more dangerous when it does not arise due to overeating, but because of edema. Usually in such cases, weight gain occurs in a short period of time (more than a kilogram per week). This may be the first symptom of dropsy – excess fluid accumulation in the body tissues, the main cause of which is the disorder of the kidneys.

It is absolutely not recommended to solve such problems on your own. Therefore, with a sudden increase in body weight, a pregnant woman should immediately consult a doctor.

And in order to notice the threatening state in time and take measures, the future mother should know the average weight gain during pregnancy.

Why Do Pregnant Women Gain Weight?

Contrary to popular belief, pregnant women gain weight not only due to the mass of the growing baby and the fat layer – they make up only about half of the total figure. Over the course of nine months, the woman’s uterus and the volume of blood and intercellular fluid increases, amniotic fluid and placenta are formed. What’s more, the mammary glands begin to grow actively.

average weight gain during pregnancy. Measuring tape around pregnant belly

These changes are necessary for the correct growth and development of the baby. It means that, not only the gynecologist, but also the woman herself should track the changes in the average weight gain during pregnancy.

Causes of the Average Weight Gain During Pregnancy

A woman during pregnancy should gain from 9 to 14 kg. While waiting for twins the figure increases to 16 – 21 kg. It is worth emphasizing that this indicator is calculated on the basis of the average data, and can vary upward and downward.

In the first trimester, weight does not change much: a woman usually gains no more than 2 kg. Starting from the second trimester, it changes more rapidly: 1 kg per month (or up to 300 g per week). After seven months – up to 400 g per week (about 50 g per day). A bad sign is a complete lack of weight gain or its rapid leap.

Such a calculation does not always show a real picture of average weight gain during pregnancy. Keep in mind that it is very individual. Some women can gain a lot of weight at the very beginning of pregnancy, while others, on the contrary, just before giving birth.

The main part of gained kilograms falls on the share of the child, whose weight, on average, is about 3-4 kg. Exactly the same number doctors give for fat deposits. Uterus and amniotic fluid weigh up to 2 kg, increase in blood volume – about 1.5-1.7 kg. At the same time, the increase in the mammary glands (0.5 kg each) should also be noted. Weight of additional fluid in the body of a pregnant woman can be from 1.5 to 2.8 kg.

Based on these calculations, the future mother can gain up to 14 kg of weight and not worry about excess eight.

Average Weight Gain During Pregnancy: Trimester by Trimester

The average weight gain during pregnancy takes place unevenly. At the beginning it is almost invisible. Then it significantly increases towards the middle and again decreases closer to the birth.

In the first trimester, both weight gain and weight loss are normal. On average, during this period, the future mother is gaining from 1.5 to 2.5 kg.

During the second trimester, when the baby begins to grow and develop particularly actively, the woman should be especially careful, as the weight gain becomes the initial value. The figures are distributed as follows: about 500 g per week for slender women, not more than 450 g for pregnant women with normal weight, and not more than 300 g for the women with excess weight.

average weight gain during pregnancy. pregnant woman on the scales

In the third trimester, pregnant women gain less weight, and this process is natural, as their bodies prepare for the baby’s appearance.

It is very important to ensure that the body weight does not decrease too sharply, as this may indicate pathologies of pregnancy development.

Why Is Slow Weight Gain Dangerous?

Slow weight gain is a relative concept for pregnant women, since in the first trimester the weight can not only not increase, but also decrease.

Some future mothers gain the first kilograms only after the 14th week. Usually it applies to slender women who do not have a genetic predisposition to obesity or women suffering from toxicosis. In the first case, the weight arrives slowly throughout the nine months, which, under the normal state of health of a pregnant woman, should not cause concern.

If we talk about women suffering from toxicosis, then by the second trimester the malaise usually disappears. The body weight comes back to normal and the weight gain goes on as usual. If a pregnant woman is starving, following a strict diet or simply improperly eats, then she has a significantly increased risk of miscarriage or premature birth.

In such a situation, a woman needs to give up restrictions and bring her diet back to normal. Eat small meals several times a day. You can also include snacks between between meals (a bite of cheese, nuts or dried fruits).

Is Fast Weight Gain During Pregnancy Dangerous?

Rapid weight gain is characteristic for multiple pregnancies, women with body weight deficiency and too young moms, whose body is still developing.

In other cases, it is the result of simple overeating and requires changes of the diet. Excess weight does not carry a direct threat to the life of the child, but can be the cause of diabetes, elevated blood pressure, pre-eclampsia and overweight of the baby. The latter can lead to complications in childbirth and even cesarean section.

average weight gain during pregnancy. after the c-section

If the weight increases too fast, a woman should consult a nutritionist and give up fast-digesting carbohydrates (sweets, muffins, pasta) and include fruits, vegetables, cereals and sour-milk products in her menu.

The situation is much more dangerous when excess weight is a consequence of edema. In order to find out the problem in time and get medical help, a future mother should know average weight gain during pregnancy and have accurate scales. An increase of more than 1 kg per week is a serious cause for concern.

What About Weight Loss During Pregnancy?

In the first trimester of pregnancy, weight loss is quite possible due to toxicosis. In the second such a situation is usually associated with various diseases and stresses. And, finally, in the third trimester the loss of 1-2 kg is a sign of an early birth.

In any case, weight gain during pregnancy is a strictly individual matter. Therefore it is very important for the future mother to monitor her health and the quality of the food she receives.

If the weight goes away quickly and sharply (especially in the first and second trimester), immediately inform the doctor. Keep in mind that this can lead to a serious threat to the health and even life of the baby.

Diet During Pregnancy

Diets, strict food systems and fasting days (especially the so-called “hungry” days) are strictly forbidden during pregnancy, even if the pregnant woman is overweight.

average weight gain during pregnancy. pregnancy diet

It is very important to make sure that the baby receives all the nutrients, vitamins and trace elements, so the future mom should not starve. You just need to balance your diet appropriately, and if necessary, get a specialist consultation.

The Rate of Weight Gain for Pregnant Women

Of course, the appearance of a certain amount of fat during pregnancy is inevitable. It is absolutely normal. After childbirth, the mum will be able to quickly regain her former weight. How many kilograms a woman will gain during pregnancy depends on a variety of reasons. The first of them is a woman’s initial weight before conception. The smaller the weight is, the more a woman can gain during pregnancy. In order to determine whether the weight of the future mother is excessive, low or normal for her height, a special indicator – body mass index (BMI) is used in medicine.

The body mass index (BMI) is a value derived from the mass (weight) and height of an individual. The BMI is defined as the body mass divided by the square of the body height, and is universally expressed in units of kg/m2, resulting from mass in kilograms and height in meters.

Body mass index = body weight in kg/ height in meters, squared.

average weight gain during pregnancy. BMI


The height of the woman is 1.70 m, the weight is 60 kg.

BMI = 60 / 1.7 * 1.7 = 20.7.

Proceeding from the received value:

  • Underweight = <18.5
  • Normal weight = 18.5–24.9
  • Overweight = 25–29.9
  • Obesity = BMI of 30 or greater.

So, if your BMI is less than 18.5, weight gain can be 12.5-18 kg. At a normal weight (BMI 18.5-25) – 10-15 kg, with excess (BMI 25-30) 7-11 kg, and with obesity (BMI> 30) 6 kg or less, according to the recommendations of your doctor.

Other Factors of Weight Gain During Pregnancy

Also one cannot forget about the genetic constitution. It is important, whether the future mother has an inclination to stoutness or leanness. So, even if the initial weight of two women is the same, but one of them has always been thin, without any diets, and the second one has achieved the same through diets and exercises, the first woman will gain significantly less weight than the second one. This should not be surprising.

Another important factor is age. The older the woman is, the greater is the tendency to excess weight gain.

average weight gain during pregnancy. woman looking at the measure tape

In addition, average weight gain during pregnancy depends on the characteristics of the course of pregnancy itself. So, for example, after an early toxicosis, the body will try to compensate for the loss of kilograms, and the woman will gain more at the end of pregnancy. It happens that in connection with hormonal changes the appetite of the future mother sharply increases. Thus, if she cannot control it, weight gain will also be significant.

The size of the fetus also plays a huge role. If a woman is expecting a large baby (more than 4000 g), then the weight of the placenta and the amount of amniotic fluid will be greater than normal. Consequently, the increase in body weight in a woman will be bigger. A particularly significant increase in weight is noted in women with multiple pregnancies. In this case, regardless of the initial weight of the mother, the average weight gain during pregnancy will be 16-21 kg.

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