Weight Gain During Pregnancy

Feb 18, 2022 | 2 minutes Read

Every woman is an individual and unique. Genetics, gender, age, environment, diet, exercise, occupation, lifestyle factors and metabolism all play a role in what any of us weigh and how much weight we gain or lose over our lifetimes.

Most women who are within an average height and weight range at the start of their pregnancy can expect to gain between 25 to 30 pounds over the full 40 weeks of gestation. This can be more in cases of multiple pregnancy or if there are pregnancy complications.

Most pregnant women have a very small weight gain within their first trimester, and some will even lose weight. Nausea, combined with changes in a normal eating pattern, can mean a weight loss of up to a couple of pounds. However, during the Second and third trimesters, most women regain what they may have lost and gradually start to gain more.

Eating for two

The old saying that pregnant women need to eat for two has no scientific basis. In fact, doubling portion sizes and increasing food volume during pregnancy is not only unnecessary, but it can also be dangerous.

What is needed is not so much an increase in  food intake  but enhancing nutrition quality. These are two very separate issues. During the first trimester, daily calorie intake should stay around the same as before pregnancy.

Later in pregnancy, most pregnant women only need to increase their calorie intake by around 10%. Current scientific evidence is clear that women who are overweight before conceiving or who gain excess weight during pregnancy can struggle to get back to a healthy weight range after their baby is born. Check your individual body mass index (BMI) for your total recommended weight gain during pregnancy.

What is body mass index?

Some maternity care providers use BMI to estimate an ideal weight gain. This is a measurement of an individual's body fat which is worked out using a mathematical formula. It is weight in kilograms divided by height in meters squared. An average BMI is between 19 and 25. Having a high or low BMI can influence the advice offered by care providers regarding how much food a pregnant woman should ideally be eating each day.

Where does the extra weight come from?

Pregnancy weight gain can be divided into how much the mother contributes to her overall gain and what her baby does. It is considered fairly normal for most women to gain around 6.5 pounds of extra body fat over the course of a normal pregnancy. Extra weight deposits around thighs, hips, bottom and arms act as reservoirs or energy stores which can be used by the mother’s body during breastfeeding. Maternal weight gain comes from:
  • Extra circulating blood volume.
  • Water retention and general fluid increase.
  • Extra weight of the breasts.
  • Extra weight of the expanding uterus.
  • Amniotic fluid and placenta.
  • The baby. At birth an average weight is around 6.5 to 7.5 pounds.
In the early stages of pregnancy, most maternal weight gain occurs because of changes within the mother, rather than the baby. More blood is produced to support the growing fetus and to supply the oxygen and nutrients it relies on to grow. And although it's normal to have an increased appetite, look to improve food quality, not increase quantity.

It is normal for there to be fluctuations and changes in a pregnant mother's weight gain. But any sudden increase or decrease can be cause for concern. Therefore, many maternity care providers monitor the weight gain of their clients as it can be an indicator of certain complications.

Some mothers are only weighed at the beginning and end of their pregnancy. A lot of pregnant women like to keep a check on their weight themselves and the best way to do this is with a weekly weigh-in, at around the same time of the day. The ideal way to gain pregnancy weight is slowly and steadily.

Sudden increases or decreases need to be checked by your maternity care provider. In a normal and uncomplicated pregnancy, there is only a small weight gain—if any—in the first trimester. Most women then gain around 1.5 to 2 pounds per week until the last 1 to 2 weeks of pregnancy, when weight gain tends to slow down.

How long will it take to lose pregnancy weight?

Many experts agree that it is fair to assume what took 9 months to gain will take around the same period of time to lose. Some women drop their pregnancy weight quickly and are back in their pre-pregnancy clothes within a couple of weeks of giving birth. Others take longer. Some women report they never return to their pre-pregnancy weight. It is rarely helpful to compare pregnancy weight gain or losses.

The same basic arithmetic for losing weight at any other time applies to after birth. The more energy which is taken into the body in the form of food, the more that energy needs to be used up. Too much food is stored as fat. To lose excess weight requires attention to portion control and some form of daily exercise. Be realistic about losing post pregnancy weight, especially if you are breastfeeding your baby. Limiting food can impact on breast milk supply.

What about dieting?

Pregnancy is not a time for a diet. Calorie restriction can lead to malnutrition and may affect the baby's growth. There is also an increased incidence of neonatal death and low birth weight babies in women who diet during their pregnancy. Losing weight too quickly after birth can lead to problems with low lactation and low energy levels.

Underweight during pregnancy

Being underweight can lead to complications such as:
  • Having a baby who is small for dates and underweight at birth.
  • Increased risk of premature delivery and the associated problems with having a preterm baby.
  • Potential problems with lactation and low breast milk supply.
Having a BMI which is too low or being very underweight can lead to problems with conception. A normal menstrual cycle is dependent on having a healthy ratio of fat to lean muscle and an adequate daily food intake.

Risks of being overweight during pregnancy

There are many risks associated with being overweight during pregnancy, such as:
  • Higher risk of complications with labor and delivery.
  • Giving birth to an overweight baby who may have problems regulating blood sugar levels.
  • Hemorrhoids, stretch marks, pelvic floor problems and urinary incontinence.
  • Feeling more uncomfortable and becoming intolerant in hot weather.
  • Backaches, leg aches, swollen feet, swollen ankles, and problems with mobility.
  • Raised blood pressure and higher incidence of preeclampsia. There is also an increased risk of developing gestational diabetes.
  • Extra strain on the vital organs such as the heart, liver, and kidneys.
  • Higher incidence of insulin resistance and type 2 diabetes.
While your baby is in your uterus, they will depend on you for nutrients and the ideal conditions they need to grow and thrive. The best advice regarding weight gain during pregnancy is to think in terms of the quality of the food you are eating, rather than the quantity. When a pregnant woman is carrying too much fat, there can be changes in the way her body works. This can impact her energy levels, mood, and general health. Excess weight can also increase the risk of pregnancy and birth complications. Learn to listen to your body's signals when you have eaten enough and are sufficiently full. Try to think in terms of being satiated during meals: that means your hunger is satisfied and you do not need to eat any more. Avoid missing meals as this can put your body into a starvation mode which leads to issues with metabolism and low energy. Speak with a dietician and your healthcare provider if you are concerned about your weight.

The information of this article has been reviewed by nursing experts of the Association of Women’s Health, Obstetric, & Neonatal Nurses (AWHONN). The content should not substitute medical advice from your personal healthcare provider. Please consult your healthcare provider for recommendations/diagnosis or treatment. For more advice from AWHONN nurses, visit Healthy Mom&Baby at health4mom.org.