A woman’s body undergoes significant changes during pregnancy – one of the more visible changes is weight gain. However, there is often confusion regarding how much weight is normal to gain during pregnancy.

 

Keep reading to learn more about weight gain in pregnancy!

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Why do women gain weight during pregnancy?

 

Weight gain during pregnancy represents the mother’s body changing to support the healthy development of her baby.

 

This change in body composition and weight is influenced by the mother’s metabolism and adaptation to pregnancy, as well as the growing placenta.

 

Approximately 1/3 of maternal weight gain is associated directly with the developing fetus, placenta, and amniotic fluid. The majority of weight gain is due to large increases in blood and fluids in the mother’s body, as well as increase in the breasts, uterus and fat stores. 
 

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How much weight should women gain during pregnancy?

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In a healthy pregnant women with a singleton (one baby) pregnancy, there is minimal weight gain in the first trimester (approximately 2-4 lbs). The majority of the weight gain is in the second and third trimester, where women have been reported to gain approximately 0.6 kg per week. These numbers would be different with a twin or triplet pregnancy. 

Recommendations are made based on a woman’s pre-pregnancy body mass index (BMI). Here is how BMI is calculated:
 

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Health Canada makes the following recommendations for singleton pregnancies:

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Although it is common to refer to pregnancy as a time to ‘eat for two’, pregnant women need only modest increases in calories with greater increases in vitamin & mineral consumption. The Society of Obstetricians and Gynaecologists of Canada (SOGC) recommends women within the normal BMI range, in the first half of pregnancy you only need to add an additional 100kcal to your diet per day. For example, 100 kcal is less than a typical granola bar in addition to your normal diet each day.  For the second half of pregnancy, this requirement increases to an additional 300 kcal per day.

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Women who are pregnant with multiple babies are expected to gain more weight, with increased weight from the babies and their tissues. Health Canada therefore makes the following recommendations for women pregnant with twins:

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Due to a lack of data, recommendations have not yet been developed regarding weight gain for women pregnant with 3 or more babies.

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Tracking the mother’s weight is a standard clinical assessment to help track the growth of the fetus. If women are not on track for normal weight gain, this may be due to medical conditions, diet or activity levels.