Starting a family may feel overwhelming. You have to consider many things to plan for a healthy pregnancy.

You have more health factors to consider if your body mass index (BMI) is in the overweight or obesity ranges.

Excess weight can impact reproductive health. But weight isn’t just a result of what you eat and how you move your body. It’s also related to genetic, societal and environmental factors. 

Diagnosing Obesity

Diagnosing obesity is more than just looking at a scale. Weight exists on a spectrum, ranging from underweight to extreme obesity. Medical professionals may use a ratio called BMI, which is weight compared to height, to determine if you have a healthy weight. The goal for most adults is to have a BMI that's over 18 and under 25. 

• Overweight: BMI of 25 to 29.9
• Obesity: BMI of 30 or higher
• Extreme obesity: BMI of 40 or higher

Although BMI serves as an initial jumping-off point, obesity is a complex health condition, and its impact on a person’s overall health can’t be measured by BMI alone.

“When we look at clinical obesity, we can’t just define the disease as having a BMI over 30. We need to look at how the disease impacts one’s overall health,” says Veronica R. Johnson, MD, an obesity medicine specialist at Northwestern Medicine.

How Obesity Impacts the Ability to Get Pregnant and Carry a Pregnancy

Obesity can contribute to conditions that make it difficult to get pregnant, including:

• Irregular menstrual cycles
• Polycystic ovary syndrome (PCOS)
• Ovulatory dysfunction, which occurs when the ovaries don't release an egg during a menstrual cycle

“Having excess body fat impacts your hormonal systems, which control your ovaries,” says Christina E. Boots, MD, a reproductive endocrinology and infertility specialist at Northwestern Medicine. “The primary way a lot of weight affects getting pregnant is just not having regular menstrual cycles and not ovulating with consistency.”

Obesity is also related to conditions that can make pregnancy more complex, including:

• Obstructive sleep apnea
• Cardiovascular diseases like high blood pressure (preeclampsia), which can lead to organ damage, stroke, seizures or death
• Blood clots
• Osteoarthritis of the knees and hips
• Gestational diabetes and insulin resistance
• Thyroid dysfunction

These conditions can increase the risk of:

• Premature delivery
• Longer labor
• Unplanned or emergency cesarean birth (C-section)

Obesity can also increase the risk of birth defects that affect the baby’s brain and spinal cord.

Obesity and Fertility Treatments

For patients with a higher BMI who undergo in vitro fertilization (IVF), a fertility treatment that involves fertilizing an egg outside the body, extra body fat can make it more challenging to get pregnant. This is because ultrasound imaging becomes more difficult.

Higher BMI may also influence egg quality, implantation success, embryo development and also increase the risk of miscarriage.

What to Do if You Have Obesity and Want to Get Pregnant

Prioritizing your health before pregnancy is important for everyone. If you have excess weight and want to get pregnant, the right care team can help you achieve your weight loss and pregnancy goals. Look for specialists in reproductive endocrinology, infertility, obesity medicine and maternal-fetal medicine.

Preconception counseling can also help you make a plan for safe weight loss and a healthy pregnancy. Your preconception weight loss plan may include:

• Nutrition counseling
• Physical activity
• Weight loss medications, including GLP-1 agonists. Doctors recommend stopping GLP-1 agonists two months before attempting to conceive.
• Referral to discuss bariatric or weight loss surgery
• Mental health counseling

For people who have lost a lot of weight, experts suggest waiting one or two years before trying to get pregnant. During this time, it’s important to try to maintain a healthy body weight. This is because weight loss can change your metabolism and affect your energy levels.

Are Weight Loss Medications Safe to Use During Pregnancy?

Short answer: No.

GLP-1 agonists can help you lose weight before pregnancy. However, doctors do not recommend using them during pregnancy.

"GLP-1 agonists shouldn’t be used during pregnancy because there isn’t enough research to show what they’ll do to a growing baby,” says Jacqueline Cherry Hairston, MD, a maternal-fetal medicine specialist at Northwestern Medicine.

Recommended Weight Gain During Pregnancy

Doctors recommend weight gain for a healthy pregnancy based on your BMI at the start of pregnancy. Here are the suggested weight gain ranges:

• Underweight (BMI less than 18.5): 28 to 40 pounds
• Normal weight (BMI 18.5 to 24.9): 25 to 35 pounds
• Overweight (BMI 25 to 29.9): 15 to 25 pounds
• Obesity (BMI 30 or higher): 11 to 20 pounds 

These numbers will be slightly higher for people carrying twins, triplets and more. Talk with your physician to find out what’s best for you.

Managing Pregnancy Weight Gain

Mental health is especially important during pregnancy. For people who have a higher weight prior to pregnancy, gaining more weight during pregnancy can be stressful.

The same can be said for people who have lost weight before pregnancy.

“Pregnancy is unique because it’s one of the few times people have a doctor say to them, ‘We expect you to gain weight.’ What that means for their mental health — to see their body change after successful weight loss — is certainly something that is a very individual experience,” says Michelle A. Kominiarek, MD, a maternal-fetal medicine specialist at Northwestern Medicine.

Additionally, after having a baby, factors like lactation, stress, lack of sleep and poor nutrition can make it hard to lose weight. This can take a toll on mental health.

Talking to a mental health professional or a therapist can help manage these changes. This support is important before, during and after pregnancy.

If you have obesity and want to plan a pregnancy, talk to your primary care clinician or OB-GYN.