Once a month, women of reproductive age go through ovulation—the process in which an egg is released from an ovary into the fallopian tubes, which can then be fertilized by sperm. At the same time, our hormones begin to fluctuate and our brain chemistry shifts, which may be an attempt to help the baby-making along. These changes are thought to increase chances of conception, with research in recent years revealing that ovulation may affect your brain, body, and behavior in surprising ways.
"Hormones affect the entire body, not just the reproductive organs, so it makes sense that our thinking, our behavior, even our appearance can change throughout our cycles," says Carol Gnatuk, MD, assistant professor of obstetrics and gynecology at Penn State Milton S. Hershey Medical Center. Here are some of the more surprising, even mysterious, symptoms you may notice during your most fertile time of the month.
Your face may get (ever so slightly) redder
First, a new study published in the journal PLoS One found that women's faces become slightly more flushed in the days leading up to and during ovulation. This makes sense, Dr. Gnatuk says, since hormones affect blood flow throughout the body. "Higher estrogen levels during ovulation can cause blood vessels to dilate, and when vessels dilate close to the skin you get more of a glow," she says.
The study authors had assumed this affect might be noticeable to men, and might begin to solve the mystery of how and why men seem to find women who are ovulating more sexually attractive. But the slight increase in redness was only detectable via very sensitive cameras—not to the naked eye, which means the jury's still out.
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You might feel more frisky (and express it in interesting ways)
Evolutionarily, it makes sense that a woman's libido goes up during the time of the month she's most fertile. But ovulating women don't just consciously think more about sex; it's on their mind in sneakier ways as well. According to a 2010 study in the Journal of Consumer Research, during ovulation women may be more likely to unconsciously buy and wear sexier clothing.
Research has also suggested that women dream more about sex in the first half of the menstrual cycle, when the body is gearing up for ovulation, compared to the second half, when your body prepares for your period. One small study found women may even have more erotic interpretations of abstract artwork (think Georgia O'Keeffe flower paintings) when they're ovulating versus later in their menstrual cycles.
"Libido isn't totally driven by hormones—if it were, sex would only be about when and not where or with who," Dr. Gnatuk says. "But certainly, estrogen and testosterone, both of which are higher during ovulation, can increase a woman's desire."
You may be more attracted to a certain type of guy
Not only might you feel more "in the mood" during ovulation, but you may also be more interested in some guys over others. Studies have shown that women tend to prefer men with sterotypically masculine traits and pay more attention to traditionally attractive guys during fertile times of the month, especially if their current partners lack manly facial features, like a square jaw.
"When we're in reproductive mode, we look for traits that we associate with good health," Dr. Gnatuk explains—and that includes healthy testosterone levels, she says, which suggest that a man is well able to produce and protect offspring.
Another 2011 study from the journal Psychological Science suggests women are better at judging men's sexual orientation when they are ovulating, perhaps since, from an evolutionary perspective, there's no sense in going after a guy who isn't interested.
Your senses might seem heightened
Ovulating women seem to be better able to detect musky odors and male pheromones than those taking oral contraceptives (which prevent ovulation), according to a small 2013 study in the journal Hormones and Behavior; another study that same year found that women may have a heightened sense of smell in general during ovulation than during other times of the month.
You may even be better at detecting potential threats to yourself and your future offspring: A preliminary 2012 study by Kyoto University researchers found that women in the luteal phase of their cycles (which begins with ovulation) were better at finding snakes hidden in photographs of flowers.
You could avoid male relatives
And finally, here's perhaps one of the most bizarre side effects of ovulation found in the research: According to a 2010 UCLA study, women avoid talking to their fathers on the phone during their most fertile times of the month. (Those who were ovulating or about to ovulate were half as likely to chat with Dad, on average.)
The researchers speculated that historically, it was in a woman's (and her offspring's) best interest to avoid male relatives—and potentially incestuous couplings—while they were fertile. Dr. Gnatuk has an alternate interpretation: "You might also argue that you don't want to talk to Dad right now because he always told you you couldn't go out with guys, and now's the time you want to do that."