Plus, when women stop taking hormonal contraceptives later, they tend to not resume using condoms, putting themselves at risk for pregnancy and sexually transmitted diseases.

Researchers from Stanford Medical School in the US analyzed data from nearly 1,200 sexual active women aged 15 to 24 visiting Planned Parenthood clinics and starting hormonal contraception. At the beginning of the study, 36 percent of the young women used condoms consistently.

Condom use dropped to 27 percent three months later. Over the year, some women discontinued using hormonal contraception, with more than half not resuming using condoms after they stopped using hormone-based contraception.

The best way to protect oneself from both pregnancy and sexually transmitted infections is to use condoms along with other contraception, which the researchers describe as the dual method use. Yet, the single largest predictor of using condoms is the attitude of the woman's partner toward condoms, says lead researcher Dr. Rachel Goldstein.

"It appears that her partner's feelings may be more important than her perceived risk of a sexually transmitted infection or her own beliefs about dual method use," Goldstein adds. "Although a woman feels like she is at risk for an STI, she may not be able to advocate for herself and successfully negotiate condom use with her partner."