A mother’s weight affects both her ability to get pregnant and the health of her pregnancy. The American Society for Reproductive Medicine (ASRM) states, “Many underweight, overweight, and obese women have no problem getting pregnant. But others will have problems conceiving, most often due to ovulation problems (failure to release eggs from the ovaries).”
We appreciate that they cover both under- and overweight women. While being overweight or obese is more common, underweight women who struggle with body image or are extreme athletes don’t always realize that their lack of weight poses as much a challenge as excess weight.
As the ASRM points out, being under- or overweight is most likely to cause ovulation issues due to weight-related hormone imbalances. However, women with a lower- or higher-than-normal body mass index (BMI) have higher-risk pregnancies because they are more prone to miscarriages, pre-term labor, gestational diabetes, and babies born with low- or high- birth weights. This is why we pay close attention to our patients’ body mass index or BMI.
Bone and muscle mass vary from person to person. So, while your weight on a scale gives us some indication of where you are in relation to the general population, physicians prefer to use a person’s BMI as the best way to monitor where their weight falls on the health spectrum.
Again, ASRM: “A BMI between 19 and 24 is considered normal; less than 19 is deemed to be underweight. A BMI between 25 and 29 is considered overweight, and greater than 30 places you in the category of obese.”
If your BMI is 18.5 or lower, your physician will ask about your exercise habits. Extreme female athletes, such as marathon/triathlon runners and some cyclists and climbers, are the most likely to have excessively low BMIs. If exercise isn’t the cause, we’ll ask about your body image, history of eating disorder or begin looking for an underlying health condition.
If you’re planning to get pregnant, visit the NIH’s BMI calculator. It’s an easy-to-use form, taking height and weight into effect to yield your current BMI. Use this figure as your benchmark and then make any lifestyle changes necessary to get yourself back into the “healthy normal” range if you find yourself on the lower or higher end.
It’s not uncommon for it to take more than a year for underweight women to get pregnant. In addition, ultra-thin women are more likely to skip periods, which means they aren’t ovulating, making it harder to get pregnant.
Once they get pregnant, women with BMIs under 19 are more likely to have:
- Pre-term labor
- Higher rates of miscarriage
- Babies with low birth weights
- Babies with stomachs that don’t develop properly (gastroschisis)
If you are underweight, speak to your physician about a pregnancy diet that will help you reach the normal BMI range. If you are an extreme athlete, it’s time to curb the exercise and activity level to the moderate range. You can up the ante again once your healthy baby is born.
Women who are overweight also struggle with hormone imbalances. This is especially common for women who have PCOS. The connection between insulin resistance, increased levels of a hormone called leptin, and excess hormone levels is often the cause for lapsed ovulation, even when there are plenty of healthy eggs in the fallopian tubes.
Women who are overweight are more likely to suffer from other pregnancy risks, including:
- High blood pressure and preeclampsia
- Miscarriage and stillbirth
- Gestational diabetes (which puts your baby at higher risk for developing type 2 diabetes later on)
- Babies with high birth weight
- Increased chance of having a C-section
Your doctor will speak to you about making lifestyle changes that support a healthy pregnancy weight, including a pre-pregnancy diet and moderate exercise plan.
If your male partner is overweight, it’s time to focus on his pre-pregnancy weight, too. Overweight and underweight males are more prone to lower sperm counts, libido, and ED issues that make it harder to conceive.
Read The Male Factor: What You Should Know When TTC to learn more about how your partner can do his part to supporting your pregnancy goals.
Are you under- or overweight and struggling to get pregnant? Then, schedule an appointment with Fertility Solutions, and we’ll help you get your family-building goals on track.