Understanding the Implantation Dip on Body Basal Temperature Charts

What Is an Implantation Dip? And Can It Help You Detect Early Pregnancy?

Basal body temperature chart with ovulation and implantation dip
On this chart, ovulation occurred on Day 15, and the implantation dip is on Day 23 (which is eight days past ovulation.). Rachel Gurevich

An implantation dip is a one-day drop in your basal body temperature (BBT) that occurs about 7 to 10 days after ovulation. This drop is seen on pregnancy charts more often than non-pregnancy charts.

But whether you get one or not, it’s no guarantee that you’re pregnant (or not!).

Here’s how to recognize an implantation dip on your BBT chart, what your actual odds are of being pregnant if you do get a dip, and what may cause it.

What Is an Implantation Dip?

If you’re looking up information on implantation dips, then I can probably assume you know the basics of basal body temperature charting.

However, just in case, here’s a very brief reminder of how basal body temperature charting works.

Your basal body temperature is your body’s temperature at rest. Your basal temperature changes based on a number of factors, including:

  • how much sleep you’ve gotten
  • the temperature of your bedroom
  • whether you’re fighting an illness
  • your hormones

We are most interested in the effect hormones have on your basal body temp.

Your basal temperature goes up a few tenths of a degree higher after you ovulate. The hormone progesterone – which increases after ovulation – causes the temperature jump.

An implantation dip is a one-day drop in temperature on a basal body temperature chart that occurs about one week after ovulation.

You wouldn’t expect a temperature drop at this time.

Usually, a dropping temperature is a sign that your period is coming or has even already arrived.

But with an implantation dip, your temp will rise right back up the next day. It lasts just one day.

The dip may just be slightly lower than the rest of your post-ovulation temperatures. Or, it may dip below the coverline on your fertility chart.

(The coverline is an imaginary horizontal line separating where your temperatures on average were before ovulation as opposed to where, on average, they are after ovulation.)

The dip appears during the luteal phase, the time between ovulation and your expected period.

Implantation of the embryo usually occurs between days 7 and 11 of the luteal phase. This is why some people attribute this sudden one-day dip in temperature to implantation.

(More why this may happen below.)

Does an Implantation Dip Mean You Are Pregnant?

FertilityFriend.com, a free fertility charting online software company, did an informal analysis of the BBT charts on their site, to see if an implantation dip might indicate pregnancy.

You can’t consider their analysis a scientific study. But the results are still interesting to consider.

They did a statistical analysis of just over 100,000 BBT charts, of both pregnant and non-pregnant women.

They looked for...

  • charts that detected ovulation
  • a dip in temperature of at least 0.3 F occurring after ovulation
  • with that drop showing up between days 5 and 12 of the luteal phase

On non-pregnancy charts that detected ovulation, 11% had an implantation dip.

On the other hand, 23% of pregnancy-positive charts had an implantation dip.

Looking at their statistics, twice as many of the pregnancy charts showed an implantation dip.

What if your chart doesn’t have a dip? Is that a bad sign?

Not at all! Approximately 75% of pregnancy BBT charts did not have the dip.

If you have the dip, does it mean you’re pregnant?

Nope. The dip did appear on non-pregnancy charts.

So while you're more likely to see a dip when you're pregnant, it is not a definitive sign of being pregnant.

I get a small "dip" on my chart almost every month, on day 7 or 8 post-ovulation. I know other women who also show "implantation dips" on their charts month after month – but they are not pregnant.

The funniest thing? On a month I was charting and got pregnant, I didn’t get an implantation dip.

What Causes an Implantation Dip?

Despite its name, we don’t know if embryo implantation causes the temporary drop in temperature.

Given that the dip is seen on non-pregnancy charts, it can’t be exclusive to pregnancy. So that probably isn’t it.

One theory is that the hormone estrogen causes the dip.

Estrogen peaks twice during your cycle.

The first (and biggest) surge occurs just before ovulation. This is what leads to fertile cervical mucus and the boost in sexual desire.

There is a second surge about midway through the luteal phase. (The luteal phase is after ovulation and before your next expected period.) This surge isn’t as high as the first, but it is still significant.

Remember that progesterone raises your body temperature?

Well, estrogen has a counter effect – it lowers your temperature.

That second surge in estrogen may be why some women have implantation dips.

Estrogen levels are also higher in women who are pregnant. This could explain why the dip is seen more frequently on pregnancy charts.

However, even non-pregnant women get the secondary estrogen surge during the luteal phase.

This explains why the dip appears on non-pregnancy charts.

(As an aside, some women notice a dip in temperature the day before they ovulate. This is also probably due to estrogen. In this case, the drop is caused by the primary surge that comes just before ovulation.)

So, Am I Pregnant… or Not??

Having an implantation dip is more likely when you are pregnant, but it is not a reliable sign of pregnancy.

You can still have fun looking for an "implantation dip" - but there's no reason to get your hopes up if you have one or feel disappointed if you don't.

More on pregnancy signs:


Is There a Such Thing as an Implantation Dip? FertilityFriend.com. Accessed on January 1, 2009. http://www.fertilityfriend.com/Faqs/Implantation-dip-study.html

Continue Reading