BookmarkBookmarkTick

It’s Not 50-50: Why Your Chances of Having a Boy Are Slightly Higher

ByAnisa Arsenault
Associate Editor
Updated
May 2020
family about to pop their gender reveal balloon
Photo: Crystal Marie Sing

Seem like everyone you know is making the “It’s a boy!” announcement? It’s not just you—it’s statistics.

Since the 17th century, scientists have noticed a slightly tilted sex ratio at birth: 51 percent of babies born are boys. So why is that? A group of biologists decided to probe further, and published their findings in a research article.

Researchers from Harvard, Oxford, Fresh Pond Research Institute and Genzyme Genetic collected 140,000 embryos created in fertility clinics and an additional 900,000 from fetal screening tests. Combined with 30 million records from live births, miscarriages and abortions, the massive amount of data made this the largest investigation of its kind.

Watch, Popular Baby Boy Names:

What’s surprising is what researchers didn’t find. There was no imbalance of male or female embryos at the time of conception. But they did discover that male and female embryo mortality rates vary throughout pregnancy, which skews the sex ratio.

In the first week or so after conception, there’s more male mortality than female. Things flip in weeks 10 through 15 when there are more female losses than male. The sex ratio levels off after around 20 weeks but then shifts in the third trimester due to excess male mortality. But when all is said and done, more female fetuses are lost during pregnancy—and that’s why we have more baby boys.

“The unbiased sex ratio at conception, the increase in the sex ratio during the first trimester, and total mortality during pregnancy being greater for females are fundamental insights into early human development,” the report states.

You can learn more about the findings in the  Proceedings of the National Academy of Sciences.

(via NPR)

Congenital Heart Defects

Jennifer L.W. Fink
Registered Nurse

5 Ways to Make Baby Smarter Before Birth

Celia Shatzman
Contributing Writer

This Common Pregnancy Condition Could Up Baby’s Risk of Autism or ADHD

Ashley Edwards Walker
Contributing Writer
Published
09/23/2019

Mom-to-Be’s Hilarious ‘Demon’ Baby Sonogram Goes Viral

Laurie Ulster
Contributing Writer
Published
09/13/2019

This Is How Mom’s and Baby’s Cells Communicate During Pregnancy

Stephanie Grassullo
Associate Editor
Published
08/22/2019

Study: Industrial Chemicals Pass From Mother to Fetus Throughout Pregnancy

Stephanie Grassullo
Associate Editor
Published
01/31/2019

Why Your Baby Is Really Kicking in the Womb, According to New Research

Stephanie Grassullo
Associate Editor
Published
11/30/2018

How Big Is Baby: Fruit & Veggie Edition

Darcy Strobel
Senior Visuals Editor

Research Shows Why Babies Need to Move in the Womb

Anisa Arsenault
Associate Editor
Published
03/12/2018

This Is How Hard Your Baby Is Kicking, According to Science

Anisa Arsenault
Associate Editor
Published
01/25/2018
Article removed.