Weight Gain During Pregnancy

Looking at weight gain during pregnancy can be tricky. It’s not a black and white indicator of healthy pregnancy. And weight is a sensitive subject in a society where emphasis is put on body shape and size. 

The guidelines on pregnancy weight gain are meant to show us if a woman is getting enough calories and nutrients for her own physical health and fetal growth. Expected weight gain is based on pre-pregnancy body mass index, or BMI, a measure or ratio of height to weight. It’s convenient to check someone’s weight and identify risks, even if the number doesn’t paint the full picture of how the pregnancy might be going. Statistics tell us that pregnancy weight gain influences the chances of preeclampsia, gestational diabetes, preterm birth, larger than expected infant at birth, and postpartum hemorrhage.

Weight gain during pregnancy includes the weight of the fetus, placenta, expanded uterus, increased fluid and blood volume, and increased maternal fat stores. Most of this growth happens in the second and third trimesters, although fluid volume does start expanding in the first trimester. According to The Institute of Medicine, recommended weight gain pregnancy is:

• For pre-pregnancy BMI <18.5 – 28-40 lb 
• For pre-pregnancy BMI 18.5-25 – 25-35 lb
• For pre-pregnancy BMI 25-30 – 15-25 lb
• For pre-pregnancy BMI >30 – 11-20 lb

Newer research suggests better pregnancy outcomes with 40-52 lb weight gain for BMI <18.5 and the up to 8 lbs, no weight gain, or weight loss with a pre-pregnancy BMI >30, 35 or 40, respectively. 

Should you worry about these weight guidelines?

The weight guidelines are meant to give us a sense of when to be concerned. But keep in mind that a person’s health history, food habits, and lifestyle often tell us more than statistics. Putting on weight quickly in early pregnancy may send up an alarm for your doctor. But was this because someone who typically didn’t eat enough improved their mealtime habits? Or were they really overdoing it with processed foods, and not paying attention to balance?

Just looking at the number on the scale compared weight gain recommendations might miss something important. A prenatal nutritionist can help you feel more confident about the meaning of your pregnancy weight changes.