Your weight — whether too high or too low — can affect your ability to get pregnant. Being overweight or underweight can also cause problems during your pregnancy. Reaching a healthy weight can help you get pregnant and improve your chances of a healthy pregnancy and baby.
How does having overweight or obesity affect my ability to get pregnant?
Extra weight can make it hard for you to get pregnant. For example, polycystic ovary syndrome, or PCOS, is one of the most common reasons for infertility in women and can also cause obesity. Overweight and obesity affect fertility by:1
Preventing ovulation. Your ovaries make the female hormone estrogen. Fat cells also make estrogen. As you gain weight, your fat cells grow and release more estrogen. Too much natural estrogen can cause your body to react as if you are taking hormonal birth control with estrogen (like the pill, shot, or vaginal ring) or are already pregnant. This can prevent you from ovulating and having a monthly period.
Preventing fertility treatments from working. Obesity may lower your chances of getting pregnant with certain fertility treatments, such as in vitro fertilization (IVF).
How does being underweight affect my ability to get pregnant?
If you are underweight (your BMI is 18.5 or less), you may have problems getting pregnant. Being underweight can cause your body to stop making estrogen. This can cause irregular menstrual cycles. You may stop ovulating and getting your period. This is especially true if you are losing weight because you are not eating enough or because you are exercising too much, which may be signs of an eating disorder like anorexia nervosa.
In order to get pregnant, you need to ovulate or release an egg from the ovary so it can be fertilized by a man’s sperm. Then your body needs to be able to support a developing baby in the womb.
Could reaching a healthy weight help me get pregnant?
Yes. Every woman is different, but studies show that for women who have overweight or obesity, losing weight raised their chances of getting pregnant. Losing weight also helped menstrual cycles return to normal.1 Talk to your doctor or nurse about how to lose weight safely.
Women who need to gain weight before getting pregnant should gain weight gradually and talk to their doctor or nurse about how to gain weight safely.
How much weight should I gain during pregnancy?
How much weight you should gain during pregnancy depends on your body mass index (BMI) before getting pregnant.
Underweight (BMI of less than 18.5), you should gain 28 to 40 pounds
Normal weight (BMI of 18.5 to 24.9), you should gain 25 to 35 pounds
Overweight (BMI of 25 to 29.9), you should gain 15 to 25 pounds
Obesity (BMI of 30 or greater), you should gain no more than 11 to 20 pounds
Talk to your doctor, nurse, or midwife about how much weight is safe to gain during pregnancy.
What are the health risks for the mother of having overweight or obesity during pregnancy?
Having overweight or obesity during pregnancy raises your risk for problems during pregnancy. Also, even if you do not have overweight or obesity, gaining more weight than recommended can cause the same problems.
Gestational hypertension (high blood pressure during pregnancy). If not controlled during pregnancy, gestational hypertension may lead to a more serious condition called preeclampsia.
Gestational diabetes (diabetes that starts during pregnancy). Having overweight or obesity raises the risk for gestational diabetes. Women who have had gestational diabetes also have a higher lifetime risk for obesity and type 2 diabetes. Gestational diabetes can cause low blood sugar in the infant. Unborn babies may also be larger, which could injure the baby or the mother during birth.
The Office on Women's Health is grateful for the medical review in 2018 by:
Kathryn McMurry, M.S., Nutrition Coordinator, National Heart, Lung, and Blood Institute
Fatima Cody-Stanford, M.D., M.P.H., M.P.A., Obesity Medicine & Nutrition, Massachusetts General Hospital Weight Center, Harvard Medical School
All material contained on these pages are free of copyright restrictions and may be copied, reproduced, or duplicated without permission of the Office on Women’s Health in the U.S. Department of Health and Human Services. Citation of the source is appreciated.