Science of Love, Sex, and Babies

Your right ovary rules

Posted in news by jenapincott on July 13, 2009

200028164-002cropIf you’re like most women you probably think ovulation is something of a meritocracy — that both ovaries do equal work, and that they alternate every cycle.

If by chance you were not taught that the ovaries soldier on left-right-left-right, then you probably think ovulation is random, like a coin toss.

The second scenario is closer to the truth, but it’s not the whole truth. At least not all the time or for most women.

Fact is, your right ovary is likelier to ovulate more often than the left. This means that in two consecutive months, the right side is probably the one doing more of the hard work of producing the dominant follicle that could become a baby.

At least this is what multiple studies have found, including here (57.7% of women have right-side ovulation), here (54.5 percent have right-side ovulation), and here (62% of total follicles are on the right), and here (larger, more numerous follicles).

Why is the right ovary often dominant?

Anatomical asymmetries between the left and right sides are thought to be the reason. The left ovarian vein drains to the left renal vein and the right ovarian vein to the inferior vena cava. The left renal vein is thought to be under higher pressure than the right and therefore drains slower. Because the left ovary drains slower, the collapsed follicle (called a corpus luteum) takes longer to clear and thereby diminishes the chance that ovulation will occur on that side the following month. No such condition exists on the right side, which is why successive right-side ovulation is more common. Estradiol and testosterone levels are also higher during a right-side cycle; this may also be related to the right ovary’s more efficient plumbing as it flushes lining-plumping hormones into the uterus.

All this leads to some fascinating statistics. For instance, right-sided ovulation favors pregnancy more often than left-sided ovulation (64 percent of pregnancies came from women’s right ovaries), according to a study in Japan that tracked nearly 2,700 natural cycles. Then again, according to another study, odds of pregnancy are best when the dominant follicle develops in the ovary opposite to where ovulation took place in the previous cycle (with pregnancy occurring more often in a right-side cycle that follows a left-side cycle) because the dominant follicles in such cycles are healthier. Even if the right ovary drains faster than the left, the corpus luteum left over from the previous cycle still negatively affects the hormonal health of the dominant follicle. Best to start with a clean slate.

Interestingly, researchers in another study speculate that right-side ovulation is dominant for most of a women’s reproductive years. Toward perimenopause women are more likely to become left-dominant, presumably because the supply of follicles in the right ovary has diminished.

Apart from ultrasound, there’s no reliable way of telling which ovary you’re ovulating from. ( I devote a section of BLONDES to why ovulation is concealed, even to women themselves.) If you think about it, perhaps that’s a good thing.

Women prefer men with big….pupils?

Posted in news by jenapincott on February 6, 2009

madmanIf the eyes are windows to the soul, women usually prefer average portals. That is, we’re comfortable with men whose pupils — the black bulls-eye of the eyeball — are medium-sized.

As detailed in BLONDES, we all pick up on pupil size unconsciously, and the size of a person’s pupils affects our perception of his or her attractiveness and desirability.

The pupil dilates and becomes up to ten times larger when a person is emotionally or sexually aroused. That pretty much explains why men prefer women with big pupils. And women’s general preference for men with medium-sized pupils is also explainable: we don’t want men who are overaroused….and potentially out of control sexually.

Unless, of course, when we want them to be.

This explains the outcome of the latest pupil-size study by Peter Caryl and his colleagues at the University of Edinburgh. The psychologists found that women who were in the fertile part of the cycles — in particular, four days before ovulation — had a stronger preference for large-pupiled men. Previous experiments also found that women who prefer “bad boys” had a preference for guys with big pupils. Big pupils may be part of a suite of male sexual cues — like strong chins and aggressive behavior — that turn women on, some more than others, and more strongly during certain days of the cycle.

Of course, the researchers only asked women to rate pictures of men, not actual in-the-flesh subjects. There might be a big difference. A woman likely to conceive might in theory prefer a bulked-up pie-eyed hunk — but in real life the oaf might send her running.

POLL: PMSbuddy — insult or asset?

Posted in news, Polls and Surveys by jenapincott on February 1, 2009

I’m amused by all the attention lavished on PMSbuddy, a free online service for men to keep track of their [wife’s, girlfriend’s, mother’s, sister’s, daughter’s] menstrual cycles. Advertised as a way of giving guys a “heads-up” at “that time of month,” the site tracks a woman’s cycle and predicts when she might be her “most irritable…when things can get intense for what may seem to be no reason at all.”

A few reactions:

1. From a reproductive standpoint, it’s actually in a gal’s best interest to keep her partner in the dark about her fertility cycles. As described in BLONDES, there are reasons why women evolved to have concealed ovulation. If your partner knows when you’re fertile, he knows when to guard you. (Of course, we inadvertently advertise our fertility anyway, albeit subtly.) And if he knows when you’re not fertile, he might go out and sleep with someone who is. Evolutionarily speaking, of course.

2. Women’s tolerance for the PMSbuddy proves that we live in a post-feminist era. Many women are genuinely OK with the concept. Yes, our moods fluctuate with our hormones — so what? However, judging from reactions online, some women are shouting sexism — and I wonder if there is a generational difference. These women are offended by the idea that their moods are predicted by hormones, at least to the degree that anyone else would notice. It suggests we have less control over our bodies and behavior than we’d like. Worse, some think PMSbuddy’s premise is that women are unstable and irrational in ways that men are not.

3. But the latter just isn’t true — that is, men are also hormonally volatile — and acknowledging this makes all the difference. As I discuss in the book, men’s testosterone levels rise and fall dramatically depending on their situation or context. Sometimes men have their own predictable cycles. Want proof? Take SuperBowl Sunday. Is your man a Steelers or Cardinals fan? How his team fares may predict whether his testosterone rises or plummets, which in turn could affect his mood for the next day or two.

Perhaps it’s time for TBuddy: a service to predict your man’s testosterone-based mood swings at “that time of season,” based on the game schedule and sports forecasting services. (A daily TBuddy may predict mood by taking into account the Dow and NASDAQ market predictions.)

Red-hot hormones

Posted in media, news by jenapincott on October 25, 2008

Kathleen Parker’s column about the McCain-Palin dynamic in the Washington Post today drew on research that shows that men discount the future when presented with images of pretty women. As discussed in my book, studies have found that high-testosterone men will opt for short-term rewards over long-term gains (i.e. a smaller amount of money now versus a larger sum in the future) when in the “mating mindset.” The theory goes that activity in the amygdala — the part of the brain associated with emotions, impulses, and sex drive — and the hypothalamus, which triggers the release of sex hormones, essentially overwhelm the rational parts of the brain.
How else to explain John McCain’s pick of Sarah Palin as his running mate? It’s the male mating mindset: short-term rewards over long-term gains.

Sarah Palin was surprisingly lovely and lively the day of her debate with Joe Biden — as observed by the snarky site, Gawker. “Where is Palin in her cycle right now?” asked the blogger, noting that the governor’s sex appeal seemed particularly strong that night, and that men were more impressed with her than were women. Multiple studies have found that women have more sex appeal when ovulating than at any other time during the month. In particular, johns in strip clubs have been found to give strippers higher tips when fertile than at any other time of their cycles.

Looking at the calendar, if Palin’s fertility window was open Oct 8, the night of the debate, it’ll likely be so again on Nov 4, Election Day.

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