Birth control has given every woman the power of being in control of her body and her choices — including relationships. The pill is designed to prevent pregnancy, but it can also influence who a woman is physically attracted to. According to a recent study published in the journal Proceedings of the National Academy of Science, women who meet their partner while on the pill are more likely to choose unattractive partners and have higher marital dissatisfaction.

The pill is believed to affect psychological processes, such as determining preferences. It can also suppress biological processes that are associated with women’s preferences for cues of partner genetic fitness, or men’s facial attractiveness.

“Given that women tend to prioritize attractiveness differently when they are on versus off hormonal contraceptive, I thought that going on or off hormonal contraceptives should affect how happy they are with their partner,” Michelle Russell, lead researcher of the study and a graduate student in psychology at Florida State University, told LiveScience.

Russell and her colleagues recruited 48 couples to follow for four years of marriage and 70 couples for one year. The researchers asked the two groups, respectively, to fill out questionnaires regarding their happiness in their relationship and with their partners over the course of four years, and one year for the second group. The couples were asked about their birth control use and their marital and sexual satisfaction. “Trained observers” were asked to rate the attractiveness of the husbands’ faces based on photographs.

The findings revealed women who began dating their husbands while on the pill who were still on the pill during their marriage were more sexually satisfied than those who were on the pill when the couple started dating but who quit after the honeymoon. However, when it came to marital satisfaction, women who began their relationships while on birth control pills became less satisfied with the marriage after stopping the medicine. This was only seen if the wife's husband was less attractive than average.

Conversely, women on birth control pills who married men who were more attractive than average were actually more satisfied in their marriages after they stopped taking the pill. Interestingly, starting birth control mid-relationship did not affect satisfaction. The researchers speculate women who married a less attractive man and then stopped the pill might become more interested in more physically attractive men, and as a result, be disappointed by her husband.

“These findings suggest that HC [hormonal contraceptives] use may have unintended implications for women's close relationships,” the researchers wrote.

The study’s design makes it difficult to show hormones caused the satisfaction changes but the researchers were able to control for several other factors that could affect this.

“We were able to control for several other factors that might affect wives' marital satisfaction, such as whether or not she was pregnant, whether or not she was trying to get pregnant and her husband's marital satisfaction," Russell said.

A similar 2011 study published in the journal Proceeding of The Royal Society Biology Letters found there are some positive and negative consequences of using the pill when a woman meets her partner. Women on the pill tend to choose men who are less attractive and worse in bed, but those women also had longer relationships by two years. The researchers suspect the pill skews the subconscious chemistry by which a woman makes a mating choice.

These two studies do warrant further research as to what type of birth control pills they are taking and the amount of estrogen they contain. The effects of these pills could be weaker or stronger depending on the amount of estrogen each pill contains. Future studies should probe further into the effects of birth control on mating choice and overall relationship satisfaction.

In the U.S., several methods of hormonal contraceptives, including emergency contraception is widely used by women. According to a Centers for Disease Control and Prevention 2014 report, nearly 100 percent of sexually experienced women ages 15 to 44 have used some form of contraception. While 93 percent of these women have used condoms at some point in their lives, roughly four out of every five women have used birth control pills.

It’s vital researchers continue to study the effects of the pill on the body and mind.

Sources: Baker LR, McNulty JK, Meltzer AL, Russell VM. The association between discontinuing hormonal contraceptives and wives’ marital satisfaction depends on husbands’ facial attractiveness. PNAS. 2014.

Burriss RP, DeBruine LM, Havlicek J et al. Relationship satisfaction and outcome in women who meet their partner while using oral contraception. Proc. R. Soc. B. 2011.