Happy father’s day to all the dads and dads-to-be out there. When I learned I was going to be a new dad, I was floored … and scared.
To counter the fear of becoming new parents, my wife and I read. And read and read and read.
We rounded up about a dozen science-backed books, scanned countless research studies, downloaded pregnancy apps, and shared hundreds of articles with each other over the following months.
What follows may not surprise an obstetrician, or even seasoned parents, but it nonetheless highlights the extraordinary human journey that is pregnancy.
Fertilization is 1-in-100-million affair.
Men release about 100 million sperm each time they ejaculate, though the semen of some especially fertile men can contain hundreds of millions of sperm.
But only a few hundred may ever reach a woman’s egg. Special receptors on the surface of an egg make sure only one gets in. (Fraternal twins occur when two sperm fertilize two eggs, while identical twins occur when one sperm fertilizes one egg and it splits into two embryos.)
Source: US National Library of Medicine/MedlinePlus, Oakland University
Babies are about 15 days younger than the length of a pregnancy.
Since 1836, doctors have marked the first day of a woman’s last menstrual period as the first day of pregnancy, or “gestational age,” not when a sperm fertilizes an egg.
Ovulation happens about two weeks after a period, on average, and fertilization happens within 24 hours of that. This means if you’re eight weeks pregnant, your baby is about six weeks old.
Doctors still use gestational age, not ovulation age (also called postconceptional age) because it’s hard to detect ovulation and fertilization even more so. Periods, meanwhile, are hard to miss — and easier to notice when they’ve gone missing.
Sources: American Pregnancy Association, “Williams Obstetrics”, Business Insider
Most women aren’t pregnant for 9 months.
Nine months works as a very rough estimate, but this oft-said number can lead to a number of misconceptions.
First, it’s not a target; a healthy pregnancy can vary as much as five weeks around a 40-week due date. In fact, only 4% of women deliver on their 40-week due date.
The typical pregnancy — measured from ovulation, not the last menstrual period (which is standard) — actually lasts about eight months and 24 days, not nine months.
Source: Business Insider
Babies float around in the womb for the first week of life.
It takes the first tiny ball of dividing cells a few days to move down the Fallopian tubes and reach the uterus, and another few days for the embryo to implant itself.
From there, it embeds into the cushy wall of a woman’s uterus, soaks up nutrients, and triggers a cascade of further development.
But up until that point, babies are womb drifters.
Sources: University of California San Francisco Medical Center, NYU School of Medicine
A developing baby’s heart starts pumping blood at six weeks.
By week eight, a baby’s heart beats regularly about 160 times a minute. The pumping is also audible with the help of an ultrasound device.
When I first heard my baby’s heartbeat through ultrasound, at about week eight or nine, I laughed out of shock.
Source: Mayo Clinic
Babies can hear inside (and outside) the womb, and the uterus is very noisy.
Most of the ear structures required to pick up sound are formed by week 16. From then on, a mom’s heartbeat, eating, breathing, walking, talking, exercising, burping, and digestive gurgling can easily be heard by a developing baby.
This may help explain why babies find noise so comforting. There’s also some evidence to suggest babies learn to recognize and react to mom’s voice while inside the womb.
Sources: Pediatrics, CDC, WhatToExpect.com
Loud noises can damage a fetus’ hearing.
The sounds a mom exposes herself to are what a baby is exposed to as well, but babies can’t put in ear plugs.
The CDC says moms should avoid very loud noises exceeding 115 dBA — chainsaws, gunfire, jet engines, blaring music, loud concerts, and so forth.
Consistent loud noise (like heavy machinery) can also damage a baby’s hearing in the womb.
Sources: Pediatrics, CDC, WhatToExpect.com
Babies open their eyes inside the womb and can see light from the outside.
Although a baby’s eyes can “see” light starting around week 16, their peepers aren’t fully formed until about week 20. The eyes first open between weeks 26 and 28.
Their vision is rather blurry, but they can see — and respond with a flutter of activity to — bright sources of light like the sun or a flashlight pointed at a woman’s belly.
Getting outside often might even help a baby’s eyes develop and reduce the risk of a few eye disorders.
Sources: Office on Women’s Health, WhatToExpect.com
Women may become more easily disgusted, and possibly fearful of outsiders, during pregnancy.
Morning sickness is no fun, but a popular scientific explanation for all those waves of disgust, nausea, and vomiting suggests that it helps protect a woman’s fetus during her first trimester (or first 12 weeks).
This “disease-threat” model goes something like this: Anything that looks or smells or feels or tastes funny is more likely to gross out a pregnant woman, thus protecting her developing baby from toxic and potentially infectious things while her immune system is partially weakened.
A study in 2007 took that idea a step further, asking if pregnant women are more likely to instinctively avoid foreigners, strangers, and other “outgroups.” It found some preliminary though inconclusive evidence in a group of 206 pregnant women, suggesting they may perceive “outgroups” more negatively during the first trimester.
Sources: “Origins: How the Nine Months Before Birth Shape the Rest of Our Lives“, Philosophical Transactions of the Royal Society B, The American Naturalist, American Pregnancy Association, Evolution and Human Behavior
Babies swim in and drink their own pee for about 25 weeks.
Babies start to pee inside the amniotic sac around week eight, though urine production really picks up between weeks 13 and 16 (when kidney development is more complete).
They can start drinking this mix of pee and amniotic fluid around week 10 or 11, or when a layer of cells blocking their mouths — called the buccopharyngeal membrane — ruptures, allowing the baby to swallow. By week 20 most of the amniotic fluid is urine.
Cheers,