Celebrity news reporter Giuliana Rancic famously publicized her infertility struggles on her reality TV show. And in an interview with Barbara Walters, she admitted that her doctor told her to gain weight to improve her chances of becoming pregnant [source: Glines].
As it so happens, very thin women like Rancic tend to have more trouble conceiving than obese women do. A recent study examined three groups of women seeking in vitro fertilization (IVF) procedures: very thin, normal weight and obese. The normal-weight women had a 50 percent success rate with IVF, obese women had 45 percent and thin women had only 34 percent [source: Macrae].
Low bodyweight can also prevent a woman from conceiving naturally. One possible reason for this is that being underweight can lead to amenorrhea, the absence of menstrual periods [source: Mayo Clinic]. If you're experiencing amenorrhea, you're not ovulating. Thin women may also have irregular periods, which can lead to inconsistent ovulation.
A man who's too thin can be infertile as well. Just as being overweight can reduce a man's sperm count, so can being underweight [source: Levine].
So don't think you're off scot-free just because you're not overweight or obese. If you're having a difficult time conceiving and either you or your partner has a body mass index (BMI) under 18.5, you should consider a healthy weight-gain regimen recommended by a dietitian or physical trainer.
For more tips on improving your fertility, click on the next page.