When Are You Officially Pregnant? Here's How To Calculate

If you’re trying to conceive like I am, everything feels like a numbers game. When is your fertile period? What exact day are you ovulating? Are you sure? Which method of sex works best: every other day? Every day? The day of ovulation only? (How romantic.) Another question at the forefront of your mind is, when are you officially pregnant?

This is important information to have if you’re trying to ensure you’re not super pregnant during the summer months, especially if you live in the humid south, like me. I’ve heard southern summer pregnancies are terrible — being puffy, sticky, sweaty, and hot from the summer heat on top of having those symptoms from being pregnant? Yikes. And most importantly, it’s also good to know when you’re officially pregnant for when you’re trying to figure out the progress of your baby. There are ultrasounds to schedule, milestones to hit, progress to track, and birth plans to make.

Even Dr. Sarah Winward, who has a doctorate of naturopathy, is a birth doula and a founder of Your Downtown Doula in Toronto, says when you’re "officially pregnant" is a tricky question to answer.

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But the very short answer is this: "You are officially pregnant when a fertilized egg implants into the uterus, and this usually happens at around the third week of your cycle," Winward says in an email to Romper.

The average woman’s cycle ranges between 28 and 32 days, but some women’s cycles can be shorter or longer, noted the American Pregnancy Association (APA). And if you’re trying to conceive, you can calculate your ovulation day by "starting with the first day of your last period, and then calculating 12 to 16 days from your next expected period," according to the APA.

Winward says, "Fertilization happens around the second week of your cycle (day 14 on average), but it takes about a week for the fertilized egg to travel from the fallopian tubes to the uterus. The reason why we use the last menstrual period to track time from conception is because not all women ovulate on day 14, so not all conception happens at this time, [and] on top of that, women don’t always ovulate on the same day every cycle, so you may not even know what day it was."

But you definitely know when your last period was, so you can’t really miss that.

Therefore, technically, the amount of time between conception and birth is 38 weeks, "but we add on two more weeks because we start counting from the last menstrual period, giving you 40 weeks of pregnancy," Winward says. "Pregnancy tests work by measuring a hormone called hCG, which your body produces to help sustain a pregnancy early on."

Winward says most home pregnancy tests aren’t sensitive enough to pick up the small amount of hCG produced during implantation, when the fertilized egg "implants" itself into the uterus.

"Which means the earliest possible pregnancy test you could take would be three weeks into your cycle," she says. "For people undergoing fertility treatments, hCG is usually measured in a blood test, which can detect pregnancy a few days earlier than most urine tests. Doctors and midwives will almost always use the date of your last menstrual period to track how far along you are," Winward adds. "However, if your cycle is consistently long, they may assume that you ovulate a little later than day 14."

For some women, the day they turn a pregnancy test is the day they are "officially pregnant." But scientifically, it happens much sooner than even some women can detect. If you’re trying to conceive, ovulation predictor kits (OPKs) are a great tool to use while trying to calculate when you "do the deed" to make a baby. I’ve personally found that apps like the Ovia Fertility Tracker & Ovulation Calculator and Period Tracker: PMS & Ovulation Tracker are great tools to help navigate the world of conception.