Implantation Dips

If you are taking your basal body temperature each morning (BBT) you probably have heard about implantation dips. They are a small thermal drop in your chart during the luteal phase that last only one day. They usually occur during the window of implantation, or around 7-11 dpo. The idea is that when the blastocyst is implanting into the uterine lining, the body produces a surge of estrogen. Estrogen lowers temperature, progesterone raises temperature. So, the BBT will show that estrogen surge in a temperature dip.

A note: If you see a dip at 2-4 dpo, this is NOT an implantation dip. Implantation dips can only happen after the blastocyst has hatched from it's "shell", which occurs between 4-6dpo. I am an early hatcher, so I know mine hatch around 4 dpo. It can be as long as to the end of 6 days before you get an actual hatch, though.

On this chart, there is a small dip at 3 DPO. This is NOT an implantation dip.

 On this chart, there is a dip at 2 DPO. This is NOT an implantation dip. The 5 DPO dip COULD be an implantation dip, but it's not likely.

This chart shows an implantation dip at 7 DPO. This IS a pregnancy chart, but ends in a miscarriage. It is likely that the blastocyst implanted at 6 DPO (more on that later.)

This is my current chart. It COULD be an implantation dip, as it occurs at 7 dpo (6/8). That does not guarantee that this is a pregnancy chart or that I will get a positive test. If I do get pregnant this cycle, it is likely that I had a blastocyst implant at 6 DPO (5/7). (Again, more on that later.)

They are a THEORY, not a fact. Some women will never get an implantation dip and they are pregnant. Others will always get a dip around that time and they are not pregnant.

Now my theory about implantation dips: I believe if you see a dip then the estrogen surge and implantation has already happened. Just like with determining ovulation, where the rise means that ovulation occurred on the last day of low temperatures, an implantation dip means that the estrogen surge relating to the dip occurred the day before the dip and can only be reflected the next day.

So if you see a dip at 7 DPO, it is likely that the dip is reflecting a hormonal shift from the previous 12-24 hours. So it is likely implantation occured at 6 DPO. If a dip is seen at 9 DPO, it is more likely that the actual implant and estrogen surge began at 8 DPO and is only being reflected in the chart the day after.

Make sense? Remember, it's just a theory, and it's just something I've been musing over.