Although it happens every day and appears to be a simple process, several conditions must be met for a woman to successfully conceive. One of these is that she should be neither overweight nor underweight -- either condition may have a negative effect on conception. Achieving a proper weight can help a woman who is having trouble conceiving.
Anyone with a low body mass index may have trouble getting pregnant according to the Advanced Fertility Center of Chicago. If your BMI is below 18.5, you are considered underweight at a level that may be problematic for conception. For example, a woman who is 5 feet 4 inches and weighs 105 lbs. has a BMI of 18 and may not be able to conceive. Even if you're only slightly underweight, it can impair your ability to get pregnant.
How It Affects Ovulation
You typically need at least 17 percent total body fat to ovulate regularly. Ovulation involves the release of an egg from your ovaries, which continues into your uterus to get fertilized by a sperm. BabyCenter.com says that if there is too little body fat, it could disrupt the hormone flow from the brain to the pituitary glands that encourages the ovaries to release an egg. In this case, you will not ovulate or get your period.
How It Affects Fertility
Women who do not ovulate cannot get pregnant. Akashia Anderson of the Vanderbilt University Psychology Department says that women who have even 10 to 15 percent too little body fat may have either irregular menstrual cycles or a complete cessation of menstruation. Without ovulation, pregnancy cannot occur under any circumstances. Some women who are underweight can go for many years without having a period. Some women may have infertile bleeding, so getting a monthly period is not necessarily an indication that you are fertile.
What to Do
Fortunately, most women who gain the necessary weight to reach an ideal BMI will be able to correct their infertility and go on to get pregnant if all other conditions are in place. This may involve reducing your workout routine if you exercise to maintain low body fat or increasing the amount of fat that you consume in your diet. After weight gain, most women start to ovulate regularly, and if they don't, there are procedures to help them if they maintain their new weight.