A Gynecologist Explains Exactly When to Test for Pregnancy

Original illustration by Stephanie DeAngelis

Although I'm nowhere near having kids myself, I had dinner with a few married couples recently-I was seventh-wheeling as usual-and the topic of fertility came up. What I learned during this conversation that I hadn't realized before was just how scientific the whole process of conception is and that there is actually a specific time period for when to test for pregnancy, too. Through our talk, I realized just how little I knew about ovulation, missed periods, and taking a pregnancy test (and that it's not always the type of test you use but when you take it that can lead to a false negative).
Since I know I'm not the only one out there with questions, I decided to tap Anate Brauer, MD, a board-certified reproductive endocrinologist and ob-gyn, to ask some of the most important questions about when to test for pregnancy (you can thank me later). Brauer says that if you experience a missed period, nausea, mood changes, enlarged breasts or breast tenderness, fatigue, increased urination, cramping, bloating, constipation, heartburn, an increased sense of smell, congestion, changes in food cravings, or dizziness, you may be pregnant. But these signs alone won't confirm your feeling, which is why we've asked Brauer to give us the lowdown on when to test for pregnancy. Keep reading for the details.

What is a pregnancy test actually testing?

“Basically, the basis of all pregnancy tests-blood or urine-is the detection of human chorionic gonadotropin (hCG),” says Brauer. This hormone is secreted into the maternal bloodstream after implantation. FYI: Implantation usually occurs about six to 12 days post-ovulation.

What are my testing options?

You can take a urine pregnancy (or at-home) test or take a blood test in the doctor's office. When it comes to an at-home test, there are fibers on the “stick” that contain chemicals that react when hCG is present. If there is a reaction, it produces a line, which indicates you're pregnant. And you guessed it: No line indicates you are not expecting.

As for the second option, “blood pregnancy tests can detect the hormone of pregnancy much sooner than urine tests,” says Brauer. And they can actually detect much more than that-including whether you're having a healthy pregnancy. Brauer says when she is working with patients who are trying to conceive, she tests their hCG level every two to three days upon having a missed period since an elevated level is a positive indication. “We generally expect to see a doubling of hCG values every two to three days in normal pregnancies,” she says. “A slow rise may indicate that the pregnancy is abnormal and may even detect the possibility of an eptopic pregnancy.”

What is the best at-home test?

“The bottom line is if you want the most sensitive and reliable pregnancy test as early as possible, a quantitative hCG test with your doctor is likely the way to go,” says Brauer. That being said, there are certain situations when it might not be possible to visit your doctor right away (or maybe you're impatient). According to a 2011 study, Brauer said that that the First Response manual and First Response Gold digital devices were the most effective of those that were tested-they actually detected more than 97% of pregnancies by the first day of a missed period.

What is the “sweet spot” for taking the test?

In general, Brauer says that pregnancy tests should be taken 10 to 14 days after ovulation. “It should be noted that some women ovulate late in their cycle,” the doctor says. “So testing for pregnancy on 'day 28' of a cycle may be too soon for someone who ovulates on day 22 (which can occur in women with irregular or absent periods).” You can download an ovulation app like Glow or Kindara, or consult a reproductive endocrinologist who can provide a customized timeline for when to have intercourse as well as when to test.

What are my chances of a false positive or false negative?

A false negative is possible if you take the test too early (see the details on ovulation and testing above). You should also try to avoid making errors when you perform an at-home test. “Read the instruction manual carefully before proceeding,” says Brauer. Sometimes during a blood test, there are human antibodies that will turn the test positive (although these usually won't affect a urine test). “hCG can be produced by entities other than pregnancy such as a tumor,” says Brauer. “While this is rare, all positive hCG tests should be confirmed with the visualization of a pregnancy on ultrasound.” Also worth noting, some fertility treatment medications may contain hCG-if you test too soon after taking the medication, you can have a false positive.