You may already know that a healthy weight influences a pregnancy, but you may be surprised to learn that your weight can determine whether or not you become pregnant. Some women who are underweight or overweight don’t have problems with conception, but for others, problems related to weight can impair fertility. Don’t launch an effort to gain or lose weight independently. A healthy body weight is a preconception goal that you should discuss with your health care provider.
Calculating your body mass index, or BMI, is a good starting place to determine if you are underweight or overweight. Your BMI is an estimation of your body fat based on your height and weight. You can easily determine your BMI by utilizing an online calculator that simply requires you to enter your height and weight. A BMI range of 19 to 24 is normal, and a BMI of less than 19 suggests that you are underweight. A BMI range of 25 to 29 is overweight, and a BMI above 30 falls within the obese category.
Your doctor can best determine if your weight is an obstacle to pregnancy and design a plan to address your needs. She may modify your diet and add exercise to your daily routine. For example, if you are overweight or obese, your doctor may recommend an exercise plan and a diet that restricts your daily caloric intake. Weight loss surgery is a treatment option for women with a BMI greater than 40. If you are underweight, your doctor may recommend a diet that increases the number of calories you consume each day. Such a diet might include more frequent meals, snacks, juices and milk to increase your body fat.
Being underweight can stop you becoming pregnant by stopping ovulation and triggering irregular menstrual cycles. Normal ovulation requires 17 percent body fat. Athletes and women who engage in a stringent exercise regimen may lack enough body fat to ovulate regularly. Lower body fat interferes with the delivery of hormones to the pituitary gland, which cues your ovaries to release an egg.
Being overweight can present several obstacles to pregnancy. Irregular ovulation and irregular menstrual cycles can thwart your efforts to become pregnant if you are overweight. Conception can still remain problematic for women who do ovulate regularly. For overweight women who ovulate regularly, fertilization may not occur when the hormone leptin is disrupted. In the September 2010 issue of the journal "Reproduction," researchers studying the effects of obesity on conception and implantation found that women with a BMI higher than 30 were less likely to respond to fertility treatments and more likely to have problems with implantation.