Pregnancy is a time of changes within the body. It is normal to gain some weight during pregnancy due to the growth of the baby, placenta, and fluid around the baby (amniotic fluid).
The amount of weight that you should gain during pregnancy depends on your pre-pregnancy body mass index (BMI). This is your weight (measured) in kilograms divided by your height (measured) in meters squared. You can ask your health practitioner to help you with this, especially if you do not have accurate scales at home.
For example: if you are 1.68 m tall and weigh 82 kg:
Your BMI = = 29 kg/m2 = Overweight category (orange colour)
Alternatively, you can use the chart below to help you. Find your height, then go across the chart till you are in the column headed by your weight (kg). The number in the cell is your BMI (rounded to the nearest whole number). The color of the cell indicates which recommendations are right for you.
In the first trimester (first 12 weeks), most women do not need to gain much weight (usually less than 2 kg) – which is just as well for those who have morning sickness early in pregnancy. Some women even lose a small amount of weight. If this happens to you, you do not need to be concerned as long as you start to gain weight steadily in the second and third trimesters of your pregnancy.
The table below can be used as a guide to help you work out how much weight you should gain during your pregnancy. Regardless of your BMI at the start of pregnancy, you can still have a healthy weight gain during pregnancy.
Most women do not gain much weight during the first trimester of pregnancy (between half and 2 kilograms). The rate of weight gain can vary during the rest of your pregnancy and may not be the same every week.
|Pre-pregnancy or early pregnancy (less than 10 weeks) BMI (kg/m2)||Total weight gain range|
|Underweight (<18.5)||12.5 kg–18 kg|
|Healthy weight (18.5 – 24.9)||11.5 kg–16 kg|
|Overweight (25.0 – 29.9)||7 kg–11.5 kg|
|Obese (≥ 30.0)||5 kg–9 kg|
Source: IOM and NRC 2009
It is especially important to gain the right amount of weight when you’re expecting twins because your weight affects the babies’ weight. And because twins are often born before the due date, higher birth weight is important for their health. It is important you work with your health care provider to determine what’s right for you.
Consider these general guidelines for pregnancy weight gain if you’re carrying twins:
|Pre-pregnancy or early pregnancy BMI (kg/m2)||Recommended weight gain|
|Healthy weight (BMI 18.5 to 24.9)||17 kg–25 kg|
|Overweight (BMI 25 to 29.9)||14 kg–23 kg|
|Obese (BMI 30 or more)||11 kg–19 kg|
Source: IOM and NRC 2009
Pregnancy is a unique time in which your body changes to meet the needs of your growing baby. Your body must store nutrients and increase the amount of blood and other fluids it makes.
Here is an example of how much each component part weighs during pregnancy if your baby’s birth weight is 3.5 kg, and you gained 12.8 kg during your pregnancy:
|Fluid around the baby (Amniotic fluid)||0.9 kg|
|Growth of your womb (uterus)||0.9 kg|
|Growth of your breasts||1.1 kg|
|Increased amount of blood||1.5 kg|
|Increased amount of other body fluids||1.1 kg|
|Storing of nutrients (fat and protein)||3.1 kg|
|Total weight gain based on this example||12.8 kg|
Dieting to lose weight during pregnancy is not recommended.
While it is ideal to be a healthy weight before becoming pregnant (ie, a BMI between 18.5 and 24.9), we know that this doesn’t always happen! If you are outside the healthy weight range, you can still help your baby by gaining weight within the recommended range for your BMI category.
Talk to your lead maternity carer about how you can monitor your weight, and for advice about eating and being active during your pregnancy.
Here are some tips to help you manage healthy weight gain during pregnancy.
(The Ministry of Health acknowledges the work of E Jeffs and Canterbury DHB in producing these tips.)
Gaining the right amount of weight during pregnancy through a mixture of good eating and activity choices will make returning to your pre-pregnancy weight easier.
If you were overweight or obese before becoming pregnant but established good eating and activity habits during pregnancy, continuing to do so after your baby is born will help support gradual weight loss. This will not adversely affect the ability to breastfeed or the quantity or quality of your breast milk.
The greatest amount of weight loss usually occurs in the first 3 months after birth and then continues at a slow and steady rate until 6 months after birth. Breastfeeding helps you return to your pre-pregnancy weight as some of the weight you gain during pregnancy is used as fuel to make breast milk.
If you are planning another pregnancy, it is a good idea to establish healthy eating and activity patterns and try to reach a healthy weight before becoming pregnant. For some, this will be a matter of returning to your pre-pregnancy weight or close to it.
Retaining excess weight over subsequent pregnancies increases your risk of developing diabetes and heart disease later in life.
Speak to your lead maternity carer for more advice.
Don’t forget to take an 800 mcg tablet of folic acid each day if you are trying to become pregnant!
Source: Dept of Health, NZ