Pregnancy and Biology 101

I originally titled this “Pregnancy 101 for Guys,” but given the state of sex education in the U.S., I suspect many of us need some additional learning regardless of gender. But I’m mostly looking at my fellow guys with this thing, especially with all of the recent debate and discussion. Some of this is information I wish I’d learned sooner. Hopefully it will be helpful to others.

This is a very incomplete list. Factual corrections are appreciated. And if you’ve encountered additional myths that need busting, feel free to add them to the comments. (I considered just turning comments off, but I’ll leave them open for now and we’ll see what happens.)

Periods can’t be turned on and off like a tap.

I don’t even know what to say to this one, which came from a Twitter thread. But, um…

  • Periods happen when the uterus sheds its lining, resulting in bleeding from the vagina.
  • Periods generally happen about once a month, and last for about 5 days. Neither of these numbers are exact.
  • For some people, periods are relatively regular and predictable. For others, not so much.
  • No, it’s not like peeing. You can’t just “hold it.” WTF is wrong with you, man?

Fertility is cyclical.

About halfway through the menstrual cycle, the ovary releases an egg into the fallopian tube. That egg lives about 12-24 hours after leaving the ovary. If it’s not fertilized, the egg dissolves, and the cycle continues.

This doesn’t mean there’s only a 12-24 hour window when sex can result in pregnancy. Sperm can survive up to five days in the fallopian tubes. If you and your partner have sex, and your partner ovulates two days later, that’s when sperm and egg would potentially meet. In other words, fertilization would occur two days after you had sex.

(This should also help explain why some emergency contraception works by preventing ovulation after sex.)

Conception isn’t instantaneous.

“It can take anything from 45 minutes to 12 hours for a sperm to reach your fallopian tubes, which is where conception usually happens.” (Source)

And once the sperm reaches the egg, “it takes about 24 hours for a sperm cell to fertilize an egg.” (Source)

“X Weeks Pregnant” isn’t the number of weeks from conception.

“Gestational age is the common term used during pregnancy to describe how far along the pregnancy is. It is measured in weeks, from the first day of the woman’s last menstrual cycle to the current date. A normal pregnancy can range from 38 to 42 weeks.” (Source)

In other words, someone who is “six weeks pregnant” has not actually been pregnant for six weeks.

Pregnancy tests don’t work instantly after conception.

“If you are pregnant, your body needs time to develop detectable levels of [human chorionic gonadotropin (HCG)]. This typically takes seven to 12 days after successful implantation of an egg.” (Source)

Healthline advises waiting until the week after your missed period for an accurate pregnancy test result.

If the average menstrual cycle is 28, and gestational age is measured from the first day of the last menstrual cycle, this means you’re already considered to be a minimum of five to six weeks pregnant by the time you get an accurate result from your pregnancy test.

Conception =/= Pregnant.

“Conception doesn’t always mean that a pregnancy will occur and be carried to full term.” (Source)

The American College of Obstetricians and Gynecologists notes, “Fertilization, the union of an egg and a sperm into a single cell, is the first step in a complex series of events that leads to pregnancy.” (Source, Emphasis added)

It takes around a week, give or take, for the fertilized egg to implant in the uterine lining.

Whether you agree or disagree — and I have no doubt people will continue to argue this one — the ACOG has stated that “pregnancy begins upon the implantation of a fertilized egg into the lining of a woman’s uterus. This typically takes place, if at all, between 5 and 9 days after fertilization of the egg – which itself can take place over the course of several days following sexual intercourse.”

What is ectopic pregnancy?

In some cases, the fertilized egg implants outside of the uterus, most often in the fallopian tube. “The fertilized egg can’t survive, and the growing tissue may cause life-threatening bleeding, if left untreated.” (Source)

The incidence of ectopic pregnancy is 1-2% in developed countries. (Source)

Ectopic pregnancy is treated with either medication or surgery to prevent the development of the fertilized, implanted egg, in essence terminating the pregnancy.

Pregnancy can be dangerous. Especially in the U.S.

“With an estimated 26.4 deaths for every 100,000 live births in 2015, America has the highest maternal mortality rate of all industrialized countries—by several times over.” (Source)

“African-American, Native American and Alaska Native women are about three times more likely to die from causes related to pregnancy, compared to white women.” (Source)

We have got to do better with health care, people…