If you’re among the hundreds of thousands of U.S. couples trying to get pregnant this season — and December is the most popular month for baby-making — 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 recently discovered 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 in announcing the results in November. Louis is 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.”

The NIH researchers studied 501 couples who were trying to conceive. The couples were part of the Longitudinal Investigation of Fertility and the Environment (LIFE). Earlier findings from the LIFE study have linked reduced fertility to high cholesterol levels in women and couples and to high concentrations of phthalates in men.