New research has found that women’s partner preferences don’t change during the menstrual cycle. The findings cast doubt on previous research that had raised concerns about the birth control pill affecting women’s relationships.

“There has been a lot of reporting about things that supposedly change before ovulation — mate preferences, even economic, and political preferences. Our data and that from other recent studies is consistent with a simpler story, namely that general sexual motivation changes,” said study author Ruben C. Arslan of the Max Planck Institute for Human Development and Leibniz-ScienceCampus.

The study was published in the Journal of Personality and Social Psychology.

The researchers were interested in studying the effects the menstrual cycle because of their implications for evolutionary theory.

“It’s one of those few cases where an evolutionary theory of human behaviour has pretty direct implications for our lives and decisions women make about their sexual lives,” Arslan explained. “Namely, we know that most hormonal contraceptives suppress ovulation and the concordant hormonal changes. Different evolutionary theories make different predictions about what changes in our psychology when a woman is about to ovulate.”

“The following might sound like I’m dumbing it down, but this is really pretty much what it boils down to: If the dual mating theory is right, taking the pill should make you more monogamous and attracted to ‘dad’ types (men who will invest in children, are not necessarily very sexually attractive). This is because the theory predicts a change in mate preferences and extra-pair desire when fertile.”

“If what I consider a simpler theory is right, and all that changes across the menstrual cycle is sexual motivation, then the pill would decrease sexual motivation on average (at least as far as hormones are concerned — of course having a more convenient contraceptive might also increase how often you want to have sex),” Arslan said.

“So, on the one hand, it is simply interesting to seek to understand human sexuality evolutionarily, such as why we have sex when it cannot lead to conception unlike many of our primate relatives.”

“On the other hand, most women would like to know more about the side effect profile of the pill, including psychological side effects. I have a few friends who have wondered whether changes in relationship satisfaction and break-ups that happened after changing contraceptive methods had something to do with hormones,” Arslan told PsyPost.

“This is difficult for one person to find out for themselves, because we do not flip a coin to make contraceptive decisions, many factors usually change at the same time.”

Arslan and his colleagues collected 26,000 daily reports from 1,043 heterosexual women in Germany, Austria, and Switzerland. All of the women were in a relationship and about 60% of the women were using some form of hormonal contraceptive. In each daily report, the women completed a surveyed designed to measure various aspects of their relationship, their clothing style, self-esteem, narcissism, sexual desire and behavior, and menstrual cycle.

The researchers found evidence that women had increased sexual desire before ovulation. When women were at the most fertile phrase of their menstrual cycle, they tended to report an increase in sexual desire directed towards both their primary partner and other potential partners. (These fluctuations in sexual desire were not observed during the cycle of women who used hormonal contraceptives.)

Women also perceived themselves as more desirable in the fertile window, but that was not associated with wearing more “sexy” or “flashy/showy” clothes. And there was no evidence that women who found their partners less sexually attractive experienced stronger increases in flirting with other men while in the fertile window. Ovulation was also not associated with changes in mate retention behavior.

“Both self-perceived sexual attractiveness and desire for the partner and other men rise before ovulation. This will not be surprising to many women who have experienced a few menstrual cycles without hormonal contraception. However, there might also be individual differences, so not all women experience this the same way,” Arslan told PsyPost.

“Previous studies sometimes reported that women who met their partner on the pill and then went off it (or vice versa) were less satisfied with their relationship. Our study, together with a number of other studies published in 2018, cast doubt on this.”

For example, one study found no evidence that changes in women’s desire for uncommitted sexual relationships were related to their hormonal status, while another failed to find evidence that preferences for facial masculinity were related to changes in women’s hormone levels.

“One contribution of our study was also simply collecting more data from more women,” Arslan said. “We also preregistered our predictions, so we would not be misled by interesting patterns in the data that you only notice after the fact. Still, I would not say that we understand all of this perfectly now. Rather, we showed that we should be more uncertain about what we think we knew from previous studies, and should do more and bigger studies in the future.”

All research includes limitations, and Arslan’s study is no different. The sample was skewed towards young adults, with an average age of 25.5 years old. But Arslan and his colleagues have research in the works that addresses some of these shortcomings.

“Our study focused on women in long-term relationships. Some evolutionary theories tie ovulatory changes to pairbonding, so in our next study, we also included single women to see whether there is a difference in ovulatory changes depending on relationship status,” Arslan explained.

“Also, although we collected more data than most previous studies, some of the effects predicted by evolutionary theory are actually fairly subtle. So, in later studies, we tried to collect even more data.”

“There was also some skepticism in the literature about whether we should even do these online diaries, because of course you can pinpoint the day of ovulation better if you use, for example, hormonal tests for the luteinising hormone surge. But of course using this online method allows us to collect far more data than if we have to get women into the lab or send them these tests in the mail,” Arslan said.

“And large amounts of data can compensate for the lower accuracy of this day counting method. So, I think by and large, our results convinced the skeptics of this. Also, we did not randomise whether women should take hormonal contraception or not.”

However, “our conclusions are consistent with the results from randomised controlled trials of hormonal contraception,” Arslan added.

The study, “Using 26,000 diary entries to show ovulatory changes in sexual desire and behavior“, was authored by Ruben C. Arslan, Katharina M. Schilling, Tanja M. Gerlach, and Lars Penke.