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In Times of Stress, More Girls are Born?

By Heather Turgeon |

Being pregnant and fetal developmentOver the last few days, science writers Amanda Schaffer and Annie Murphy Paul have been having a fascinating exchange about Paul’s new book Origins: How The Nine Months Before Birth Shape The Rest Of Our Lives.

The two writers dissect studies of how a mom’s behavior, diet, and environment affect her baby, but they also pull apart big ideas about evolution and the push and pull between mom and fetus.

As we know, when pregnancy studies make the news we often see big, flashy, guilt-inducing headlines, but Paul makes the distinction between small studies that we should approach with skepticism and those that are large and well-designed.

For example, a study published in the Lancet in 2007 looked at 12,000 women and found those who eat less than 12 oz of seafood per week are more likely to have children with increased risk for low verbal IQ, social and communication problems, and poor fine motor skills.

Another substantial study in the American Journal of Obstetrics and Gynecology found that women who gain more weight in pregnancy, even within the 25-35 pound guidelines, are more likely to have a heavier three year old.

But according to Paul, it’s not just about isolated variables like fish and pregnancy weight. What’s going on around the woman during pregnancy — the greater environmental conditions — shape what’s going on in the womb.

For example, in times of extreme stress (like in the wake of an earthquake), fewer boys are born. Why would that be?

Some studies of large-scale stress, like an earthquake in Kobe, Japan or the collapse of the Berlin wall, found a dip in boy births following the event. The theory is that weak boy babies are less likely to survive than weak girl babies. So in stressful times, boy fetuses will be more likely to abort, giving the mom another chance to get pregnant and have a girl, or a stronger boy.

Indeed, there is evidence that newborn boys are slightly more vulnerable than girls. And as Paul writes, Berkeley professor Ralph Catalano studied records of males born between 1751 to 1912 and found that when proportionally fewer boys were born (indicating times of stress), those men that were born had longer lifespans. Survival of the fittest?

It’s a truly fascinating field and I highly recommend reading the full discussion between the two writers, as well as a review of the book by Babble writer Ceridwen Morris.

More from Heather Turgeon:

How Much Do You Pay the Babysitter? Ouch.

Genetically Modified Salmon: Why I’m Not Afraid of the “Frankenfish”

Stop Telling Me to Co Sleep

Do it Now: The Perfect 10 Minute Mediation

50 Amazing Naptime Ideas

Concussions and Cars: Why Parents Worry About the Wrong Things.

Why Kids with Language Delays are More Aggressive

Top 10 Pediatric Myths

Non Stick Chemicals Linked to Higher Cholesterol in Kids

Too Many Moms Still Die in Childbirth: Report

Your Baby is About to Get Chubbier: Pediatricians Are Switching Growth Charts.

Doctors Misdiagnosed in all Cases of Infant Death From Whooping Cough

Too Much Pregnancy Weight Sets Up Babies for Obesity

Antipsychotic Medications for Toddlers?

C-Section Twice as Likely When Doctors Induce Labor.

Why I Abandoned the “Readiness” Approach to Potty Training.

More on Babble

About Heather Turgeon

heatherturgeon

Heather Turgeon

Heather Turgeon is currently writing the book The Happy Sleeper (Penguin, 2014). She's a therapist-turned-writer who authors the Science of Kids column for Babble. A northeasterner at heart, Heather lives in Los Angeles with her husband and two little ones. Read bio and latest posts → Read Heather's latest posts →

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0 thoughts on “In Times of Stress, More Girls are Born?

  1. [...] can tip the gender balance slightly — like the case I talked about earlier today of natural disasters leading to more girls, for [...]

  2. Laure68 says:

    This book really does sound interesting. I agree that most of the studies that grab big headlines are very weak, and then people wonder why one day they are telling us to do this, and the next something opposite.

    I’m glad you mentioned the importance of eating fish during pregnancy. The sad thing is that I know lots of women who were so scared of mercury in fish that they avoided fish altogether.

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