April 13, 2012
Busting 8 Pregnancy Myths
There is, arguably, more superstition surrounding pregnancy than any other so-called "medical condition." To separate fact from fiction, we examined the science behind the hearsay.
1. When you have sex determines the gender of your baby
Dads-to-be have two types of sperm: those that make baby boys and those that make baby girls. Some say that the body of a mom-to-be is more hospitable to boy sperm or girl sperm during certain times in her cycle. And so, the theories go, when a couple has sex can determine whether they conceive a Junior or a Bubette.
While a few small studies have supported timing methods for sex selection, larger, more recent studies have failed to find any correlation between the day within the fertile window a couple has sex and the gender of the baby, explained Dr. Rachel Vreeman, co-author of "Don't Swallow Your Gum! Myths, Half-Truths, and Outright Lies about Your Body and Health" (St. Martin's Griffin, 2009).
2. Predicting the sex of your baby through folklore is the same as flipping a coin.
Time to break it to grandma: Basketball-shaped bellies do not forecast boys. In a study of 104 women, published in the journal Birth in 1999, no correlations were found between a pregnant belly's size or shape and the baby's gender.
Similarly, predictions using the Chinese lunar calendar, the fetal heart rate and the Drano test (where the woman's urine is mixed with the de-clogging liquid and the resulting color allegedly reveals the baby's gender) were examined by physicians in Vancouver in 1999. None of them were reliable.
Neither is women's intuition dependably accurate, according to a 1996 article in the Journal of Reproductive Medicine. Of 110 women who professed having a strong sense of the baby's gender, roughly half were right -- the same number expected to be right if they were just guessing.
In all, scientists have found most folklore-based methods of predicting a baby's sex have the same odds as flipping a coin. "And 50/50 odds are not that bad," Vreeman said.
There may be a case for the predictive value of extreme morning sickness. Excessive, unrelenting morning sickness -- also known as hyperemesis gravidarum -- is slightly more correlated with having girls, Vreeman said.
3. Twins skip a generation.
Fraternal twins do run in families, due to a gene that can make a woman more likely to release multiple eggs during ovulation. But the hyper-ovulation gene doesn't leapfrog over certain generations. It is passed on from parent to child just like all genes are.
Evidence shows that identical twins, however, occur at random, rather than running in families. If there are many sets of carbon-copies in your family line, "it is probably just a coincidence," Vreeman stated.
4. Breastfeeding makes your breasts sag.
While infants certainly drain a lactating breast, their hunger doesn't cause long-term changes in breast firmness. Scientists have confirmed breastfeeding does not contribute to breast ptosis (the scientific name for saggy breasts).
However, multiple pregnancies, smoking and simply getting older have been correlated with droopier cleavage, according to a study of 132 women published in the Annals of Plastic Surgery in May.
5. The mom-to-be is the only one going through hormonal changes.
She's not alone: Dad's dealing with hormone shifts, too.
A study published in the journal Evolution and Human Behavior in 2000 found that over the course of his mate's pregnancy, an expectant father's testosterone levels go down and his prolactin levels go up. Researchers think this adjustment may help prime dudes to play daddy.
Your body shape will never be the same again.
"With exercise and diet, it certainly is possible to get back in the shape you were in before getting pregnant," Stone said, adding that this is easiest for people who were quite fit before conceiving.
People tend to forget that the body changes with age, with or without a pregnancy. So before blaming your saddlebags on your offspring, try counting the candles on your next birthday cake.
7. Pregnancy makes your feet grow.
While most women experience some swelling in their calves, ankles and feet during pregnancy, many can fit back into their favorite heels at some point postpartum.
But this one isn't a complete myth: Some women permanently go up a half-size over the course of a pregnancy -- and possibly even another half-size with each subsequent pregnancy.
8. "Morning" sickness only happens in the morning.
If only this were true! Thought to be caused by shifting hormones, morning sickness can strike (and often does) at any point in the day.
And it's not confined to the first trimester, as many believe, Stone said. "It can last up to 16 weeks."
OK, we'll have to make it 9 because we can't forget this one...
9. "Pregnancy brain" makes it impossible to concentrate.
This may be true in the first few months, when a 30-fold increase in progesterone makes most women really, really, sleepy. And some researchers say pregnancy hormones may make it hard for a pregnant woman to remember where she placed her keys.
But pregnancy brain may not be all bad.
In a small pilot study of 10 women, Stone and colleagues found that women tend to have increased attention spans in their third trimester. If the results are confirmed in a larger group of women -- something the researchers are currently working on -- it may be an indicator of "neuronal nesting."
"This may be nature's way of increasing the attention a mother is going to need to give a newborn," Stone said.