If you're among the hundreds of thousands of couples trying to get pregnant, experts say there are some lifestyle choices that could improve your odds.
Some are fairly obvious: Maintain a healthy weight and don't smoke.
"Good health during pregnancy starts with being healthy before you get pregnant," said Dr. Ranit Mishori, associate professor of family medicine at Georgetown University School of Medicine in Washington.
Others are more surprising, such as avoiding exposure to certain environmental chemicals, including some ultraviolet filters commonly used in sunscreen.
Scientists at the National Institutes of Health (NIH) recently found that men with high exposure to the UV filters benzophenone-2 (BP-2) and 4OH-BP had a 30 percent reduction in their ability to reproduce. There was no similar effect in women.
"Male fecundity seems to be more susceptible to these chemicals than female fecundity," even though women have greater exposure to UV filters overall, said Dr. Germaine Louis, director of the Division of Intramural Population Health Research at the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Bethesda, Md.
"Our next step is to figure out how these particular chemicals may be affecting couple fecundity or time to pregnancy — whether it's by diminishing sperm quality or inhibiting reproduction some other way," Louis said.
The NIH researchers studied 501 couples who were trying to conceive. The couples were part of the Longitudinal Investigation of Fertility and the Environment. Earlier findings from the study have linked reduced fertility to high cholesterol levels in women and couples and to high concentrations of phthalates in men.
See doctor for assessment
Dr. Sandra Carson, an obstetrician and reproductive endocrinologist from Brown University who serves as vice president of education for the American Congress of Obstetricians and Gynecologists, said her most important advice for a woman who wants to start a family is to see her doctor for an assessment of current health.
"The best thing she can do for herself is to be in the best shape she can be," Carson said. "Make sure all her immunizations are up to date. Make sure she's on folic acid. Make sure she knows about ovulation and when to have sex to maximize her chances, and she knows about good health in general."
Taking a folic acid supplement both before and during pregnancy is important, doctors say, because it helps prevent defects in the development of the fetal brain and spinal cord. That development takes place in the first three to four weeks of pregnancy, so doctors recommend starting a supplement — or a prenatal multivitamin containing 400 micrograms of folic acid — at least a month before conception.
The timing of intercourse — but not position — can affect fertility. "Every day or every other day during your fertile period is best," Mishori said. "And you should know when your fertile period is. But you don't have to put a pillow under your hips or hold your legs up for half an hour. That's a myth."
You also don't have to abstain during nonfertile times unless the male partner has a low sperm count. In that case, Carson said, the couple may have to restrict intercourse to the two days right before ovulation.
"You can buy a test kit to learn when you're ovulating," Carson said.
Develop healthy habits
Avoiding cigarette smoke — her own and her partner's — can help a woman get pregnant now and long-term (because smoking has been linked to earlier menopause) and also protect the unborn child. Some studies show that women who smoke and women exposed to secondhand smoke have a greater likelihood of being infertile. Smoking by the male partner hurts in another way: It harms his semen.
"But you don't need a study to know smoking is bad," Mishori said.
Alcohol consumption is a little trickier. Some studies have shown detrimental effects on fertility as well as on the developing fetus, but others have shown that a little wine may actually enhance fertility.
"I tell women, if you don't have to drink, don't," Mishori said. "If you must drink, don't have more than two drinks a day."
High levels of caffeine — more than five cups of coffee a day — may impede fertility and increase the risk of miscarriage, Mishori said. "But one or two cups a day may be OK."
As for diet, "there are all kinds of myths," Mishori said. "Low fat, low carbohydrate, antioxidants, vitamin this or vitamin that. None has any good evidence. Don't buy supplements that promise to increase your fertility. A well-balanced diet is the way to proceed, whether or not you're intending to get pregnant."
One thing everyone agrees on is the importance of maintaining a healthy weight. "For those who are either very over- or underweight, their fertility is lowered," Mishori said.
"If you're obese, you're going to have a harder time getting pregnant," she said. "You're more likely to have pregnancy complications that will have negative effects on the fetus. And there is also a higher risk of complications in labor and delivery."
If you've heard that the best way to get pregnant is to relax and take a vacation, you might be disappointed.
"The way to get pregnant is to have sex," Carson said. "Going on vacation only helps if you have more sex."