Tag: pregnancy

Why pregnant women are calmer

Posted in news, pregnancy by jenapincott on March 30, 2010

If you were to take the Trier Social Stress Test (TSST), as nearly one hundred fifty pregnant women did in a study led by Sonja Entinger at the University of California at Irvine, you’d be led to a windowless room with a video camera and instruments that measure your vital signs. There, an assistant would ask you to sit and be hooked up to instruments that measure your vital signs. In the room you’d also find three men and women sitting at a table, waiting for you.

They are your interview panel.

Facing them belly-on, your instructions are to pretend that you’re applying for a job and must deliver a five-minute speech to convince them that you’re right for the position. Someone would say 1-2-3-GO, and you’d start babbling, hopefully coherently. If you have nothing more to say before your time is up, one of your interviewers will blandly instruct you to continue. Run out of words again and twenty seconds of eerie silence will fill the room. And when you’re finally done, you’ll be asked to do a bit of mental math — say, to count down, in increments of thirteen, from a large prime number like 54,499. Before and afterward the fifteen minute ordeal, a researcher will enter the room and hand you a swab to collect your saliva for testing.

Analyzing all the data from their study, including an analysis of body language and hormone levels of women who took the TSST, the UC Irvine researchers confirmed something remarkable: the further along a woman was in her pregnancy, the less stressful she found the stress test. Compared to their stress levels in second trimester (17 weeks), volunteers in their third trimester (31 weeks) had lower blood pressure, slower heartrates, and lesser spike in the hormone cortisol. Pregnant women also did not stress out as much as nonpregnant controls who took the same tests at the same time intervals. This was not the first study that found that pregnant women, especially those in third trimester, are calmer than nonpregnant women under the same (short and moderately stressful) circumstances. But it was the first time that the same women were tracked at different stages of gestation.

So what is that makes pregnant women more Zen as they approach their due date? The likely answer is that the body reduces the sensitivity of cortisol receptors, even though baseline levels of the stress hormone are higher. In other words, it takes more stress hormones than usual to get the nervous system all hot and bothered. At the same time, the placenta increases production of an enzyme that changes cortisol to an inactive form, meaning that less of the toxic stuff filters through to the baby. Near the end of pregnancy, probably to calm you down before labor and help you bond with the baby, your body also produces more of the nervous-system soothing hormones oxytocin and prolactin.

All this is good news for moms who are slammed with short-term mild to moderate stress late in their pregnancies.

But there’s an even bigger surprise to come out of this. You may think this is your body subconsciously protecting the baby at a time of stress. But it’s just as likely that it works the other way around: your baby protecting you (as well as herself), because her placenta is responsible for at least some of the stress-dampening response to cortisol. It’s a beautiful idea — mother and child soothing one another in the face of life’s assaults.

Are pheromones why the rhythm method doesn’t work?

Posted in news by jenapincott on August 2, 2009

Pregnancy_25_weeks For women not trying to get pregnant, life should be easy. Conception can only happen in the 12-24 hours after ovulation. Sure, sperm may last as many as 3-4 days in the genital tract, hanging around for the egg to arrive. But you’d think not having sex during the 4-5-day window would be sufficient to avoid mishaps. That’s what the rhythm method is — a natural form of birth control that relies on abstinence on fertile days.

But slips happen even among the most careful practitioners of the rhythm method. Some of this may have to do with women not keeping perfect track of their menstrual cycles or having naturally irregular cycles. (I discuss in BLONDES the evolutionary reasons why ovulation is hidden to both women and their partners.) The failure rate for rhythm method is 25 percent each year (with a perfect-use rate of 9 percent).

Why so high?

Another reason could be pheromones. The latest issue of my favorite journal, Medical Hypotheses, includes a submission that suggests that pheromones from men may cause an early ovulation in women. By invoking an early release of the egg — in advance of the expected fertile window — chances of fertilization are higher. As I mention in BLONDES, studies have the found that androstadienone, a testosterone-related compound found in men’s sweat, semen, and saliva, increases the amount of luteinizing hormone in women, which thereby triggering ovulation. It’s possible that high-testosterone men may be likelier to have this effect on their lovers. Their sweat smell alone may do the trick.

As I mentioned in an earlier post, there are other properties in semen that may also trigger early ovulation. For instance, seminal fluid contains follicle stimulating hormone (FSH) and luteinizing hormone (LH), which may coax the ovary to release an egg.

Despite the high failure rate, the Roman Catholic Chruch continues to promote the rhythm method, now renamed natural family planning (adding cervical mucus and temperature data to the regimen). Problem is, we don’t live in a clockwork universe, nor do we have clockwork bodies.

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.


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