The real reason they didn't know they were pregnant

Last year a woman named Britt shared her experience on social media: she started to have stomach pain after work one evening, so she headed to the emergency room. Several hours later, she gave birth to a healthy daughter, not realizing that she’d been pregnant for the prior seven and a half months. Her diagnosis: cryptic pregnancy.

Most women who have been pregnant can't even imagine the condition passing notice. Those who gained 50 pounds, or swelled up like toads, or threw up every day for months find it hard to believe that pregnancy could be symptom-free. At the very least, they ask, wouldn't the woman have noticed her missing period? And here's the crux of these "cryptic pregnancy" stories: No, they didn't. And if you were in their bodies, you might not, either.

For one thing, women can continue to have monthly bleeding throughout their pregnancies. Yes! It's rare, but it happens. It happened, in fact, to a neighbor of my mom's. Every single month of her pregnancy this lady had period-like bleeding. It wasn't as heavy as a regular period, but it came regularly every month.

If you had no particular reason to think you were pregnant and weren't experiencing symptoms, you too might be reassured by the monthly bleeding. Still getting my period! Can't be pregnant!

Even women who notice missing periods may have good reasons to suspect something at work other than a baby. Many, many types of modern birth control, such as IUDs and different types of contraceptive pills, reduce monthly bleeding or allow women to have periods only a few times a year rather than every month. Stress, intense exercise, weight changes, being overweight, and many other conditions can cause a woman to miss periods. And some women aren't even that regular to begin with. That's me, in fact. I didn't realize I was pregnant until almost three months into my pregnancy, because I've always had irregular periods.

In addition, I took two pregnancy tests that came out negative before a positive result. Why? I didn't bother to read the instructions on the test package, and I took the first two tests in the afternoon, after I'd spent the day drinking tea and water. When I finally read the instructions and realized I had to use morning urine for the tests, bingo, there was my extra pink line!

But if I hadn't been a getting-older-every-day woman who was desperately trying to conceive before it was too late, would I have taken that third test? Even if I had, my own little fetus could have confounded me by not showing up on the tests.

Remember, the tests look for the presence of HCG, the human growth hormone. Research suggests that the incidence of "cryptic pregnancy" is higher than we suspect, about 1 in 475 pregnancies, and that part of the reason may be because some babies don't produce a lot of HCG. 

The reasons for babies not producing much HCGOpens a new window are varied and for now, speculative. But that theory goes a long way towards explaining cryptic pregnancy.

So the next time you hear an "I didn't know I was pregnant" story, give the mom in the tale an iota of credit. She may be no more clueless than you or me, just caught up in one of the enduring mysteries of the human body.