Weight Gain During Pregnancy

The four BMI range categories in the Canadian weight classification system are shown in Table 1.2  Adults who are in the underweight category are at increased risk for having undernutrition, osteoporosis, infertility and impaired immunocompetence.²  Adults who are in the overweight or obese categories are at increased risk for type 2 diabetes, dysplipidemia (abnormal amount of cholesterol or fat in the blood), hypertension, coronary heart disease, gallbladder disease, obstructive sleep apnea and certain cancers.² 

The term 'normal' is used to describe a BMI between 18.5-24.9, and is the category with the 'least risk' in terms of developing any health problem associated with too little or too much body weight.  However, it should be noted that overall health is dependent on multiple other factors including genetic predisposition, individual weight history, age, and other health behaviours such as eating and physical activity.²

Figure 1. Pre-pregnancy body mass index of mothers, KFL&A, 2012-2013⁽³⁾

Interpretation for Figure 1

Figure 1 displays the pre-pregnancy BMI's for mothers in KFL&A in 2012 & 2013.3  Almost 40% of mothers in KFL&A from 2012 to 2013 had a BMI within normal range.  Just over one fifth of mothers were considered overweight and one quarter have a BMI in the obese range. 

Figure 2. Overweight and obese body mass index categories of mothers, KFL&A, 2012 to 2013⁽³⁾

Table 2. Overweight and obese body mass index categories of mothers, KFL&A, 2012 to 2013⁽³⁾

Interpretation for Figure 2

Figure 2 displays the various subcategories of the obese class of the BMI, as well as the total proportion of mothers in KFL&A who are overweight or obese.  Almost half of all KFL&A mothers in 2012 & 2013 were considered overweight or obese, with about 5% of mothers categorized in the obese class III.  It should be noted 11.2% of mothers are missing information on their pre-pregnancy BMI categorization.

All women should strive to achieve a normal body weight during the pre-pregnancy planning stages to improve the chance of conception and reduce the risk for maternal and fetal complications during birth and pregnancy.

Table 2. Recommended weight gain for singleton pregnancies

Interpretation for Table 2

Table 2 displays the amount of weight gain recommended for singleton pregnancies based on a mother's pre-pregnancy BMI.  Women who are overweight should gain between 7 and 11.5kg during their pregnancy, while women who are classified as obese should gain between 5 and 9kg.  Most of the weight gain will happen in the second and third trimesters, as the baby and the tissues that support the pregnancy continue to grow.  In addition, two things Health Canada recommends pregnant women do every day is be active for at least 30 minutes and eat "twice as healthy", not "twice as much".⁴  One extra snack a day is often enough to meet daily caloric needs.

Figure 3. Recommended pregnancy weight gain status of mothers, KFL&A, 2012 to 2013⁽³⁾

Interpretation for Figure 3

The recommended pregnancy weight gain status of mothers is shown in Figure 3.  About one fifth of mothers (21.2%) gain pregnancy weight that falls within the recommended pregnancy weight gain - which is based on their pre-pregnancy weight.  Over one-third of mothers (36.1%) gain more weight than is recommended based on their pre-pregnancy weight.  Note that data is missing for one fifth of mothers.

Figure 4. Recommended pregnancy weight gain status of mothers by pre-pregnancy BMI, KFL&A, 2012 to 2013⁽³⁾

Interpretation for Figure 4

Figure 4 displays the recommended weight gain status of mothers by their pre-pregnancy BMI status.  Mothers who are overweight or obese pre-pregnancy are more likely to gain more weight than recommended than mothers who have an underweight or normal pre-pregnancy BMI.

Figure 5. Recommended pregnancy weight gain status of mothers by pre-pregnancy BMI and maternal age group, KFL&A, 2012 to 2013⁽³⁾

Interpretation for Figure 5

Figure 5 displays the recommended weight gain status of mothers by their pre-pregnancy BMI status and maternal age.  The 'above recommended weight gain' category is the largest of the three categories of weight gain for all age groups.

1. Health Canada. Pregnancy weight gain calculator. Health Canada. 2012.
2. Health Canada. Canadian guidelines for body weight classification in adults.  2015.
3. BORN Information System (Fiscal years: 2012-2013) Date Extracted: June 18, 2015.
4. Health Canada. Healthy weight gain during pregnancy. Health Canada. 2012.
5. Health Canada. Prenatal nutrition guidelines for health professionals: gestational weight gain.  2015.
6. Best Start Resource Center. Obesity in Preconception and Pregnancy.  2013. Toronto, Ontario.
7. ESHRE Capri Working Group. Nutrition and reproduction in women. Human Reproduction Update 2006;12:193-207.