Can your weight affect your fertility? The short answer is YES. Fat is an endocrine organ and if you have too much of it, or too little, it can affect your reproductive function in many different ways. If you are overweight, the excess fat can lead to higher estrogen levels. Some women will stop ovulating if they are too fat or too skinny. We have all heard of young girls who are ballerinas or gymnasts with very low body fat who have delayed puberty or do not menstruate due to the very low fat content in their bodies. Girls who are overweight go through puberty earlier than normal weight girls. Excess weight may lead to anovulation (or a lack of ovulation) as well. Pregnant women who are overweight experience many more complications than normal-weight women. These complications can have a negative impact upon both the mother and the baby. So, excess weight can lead to a greater risk of infertility, miscarriages, birth defects, gestational diabetes (pregnancy induced diabetes), birth injury, gestational hypertension, preeclampsia and other issues. Overweight women are more likely to need a cesarean delivery and are much more likely to suffer complications of their surgery.
What is your ideal weight? We recommend determining your ideal weight by determining your BMI or Body Mass Index. The BMI is a measure of your weight in relation to your height. If you divide your weight in pounds by the square of your height in inches, the resulting number is your BMI. There is an easy-to-use calculator on the NIH website at http://www.nhlbisupport.com/bmi/bminojs.htm. A normal BMI is from 18.5 to 24.9. Less than 18.5 is underweight and 25 to 29 is considered overweight, while a BMI over 30 is considered obese. The normal weight range can be fairly wide. For example a BMI of 19 to 24 for a woman who is 64 inches or 5 foot 4 inches tall is 110 to 140 pounds.
As we all know, obesity is an epidemic health problem in the United States today. About one third of women in the United States are obese (BMI over 30) and many more are overweight. Many women gain excess weight during pregnancy and then are never able to lose it. The Institute of Medicine (IOM) 2009 guidelines recommends that normal-weight women gain only 25 to 35 pounds during pregnancy. Many women gain much more – 50 plus pound weight gains are common in the United States during pregnancy. If you start your pregnancy overweight, IOM recommends limited weight gain – 15 to 25 pounds, while obese women should gain only about 11 to 20 pounds. Underweight women should try to gain a little more – 28 to 40 pounds.
If you are overweight and infertile, losing weight will not necessarily solve all your fertility problem, but it will lower your risks of complications of pregnancy and usually, it will make your fertility easier to treat. You do not have to lose all your excess weight to start reaping the benefits – after even just 5 pounds of weight loss, your blood pressure will be lower, your insulin levels will be lower (leading to a lower risk of gestational diabetes), you will be healthier. Talk with your doctor about your weight and how you can get closer to a healthier weight and a healthier pregnancy.
Copyright Serena H. Chen, MD, 2011.