Do I Really Need to Lose Weight While Pregnant?

I’m pregnant and it’s my first. I’m really excited, but I’m struggling with a lot of anxiety because of my high BMI (40). My doctor has said I can’t put on any weight during my pregnancy. My question is, what does the data say about being overweight while pregnant? Does it impact my ability to give birth vaginally? My blood work is clear and I’m not pre-diabetic, but I’m assuming that doesn’t mean I won’t develop gestational diabetes later in my pregnancy? Thank you.
—Anxious First-Time Mum

First: congratulations! This is wonderful news, and I hope you are finding yourself able to celebrate.

I want to answer your question in two parts. First, let’s look at data.

It is true that BMI prior to pregnancy is correlated with a number of pregnancy complications — including gestational diabetes, preeclampsia, the need for a C-section, and having a baby who is large for gestational age. As with many things, though, it is difficult to know how strong the causality is here. And other aspects of health matter too. For example, one reason that gestational diabetes is more common in women with a higher BMI is that they are more likely to already be diabetic or pre-diabetic. The fact that you are not puts you in a different category, but this isn’t captured in the data.

It is also worth saying that even with increased risks, the vast majority of women with higher BMIs go on to have healthy, uncomplicated pregnancies.

If you are looking for something to do, there is some evidence that exercise during pregnancy can lower the risk of many of these complications, even without adjusting weight. If you like to walk or do yoga or similar, go for it.

Based on the data, it makes sense to be more alert to possible complications, especially metabolic ones. It doesn’t make sense to be ruled by anxiety or fear.

Somewhat more importantly here: I think there is reason to be very uncomfortable with the attitude of your provider. For one thing, the recommendation for weight gain for women with a BMI of over 30 is 11 to 20 pounds, not zero.

Beyond this, it sounds from your letter that you’re hearing an extensive focus on your weight, rather than on other aspects of your pregnancy. This has the effect of increasing your anxiety, but it also makes your doctor more likely to miss real issues because of the weight focus. This is not true for all doctors, by any stretch! But it colors the experience of many women.

Rather than opining myself, I’m going to suggest you read this post, by the great Virginia Sole-Smith, about issues around the treatment of pregnant women in a larger body.

And then consider a new doctor.