The term implantation dip is often used to refer to a luteal phase dip that occurs around the time of expected implantation (7-10 days past ovulation). While this pattern does not always result in pregnancy, the term is often used because of the timing of the dip and because this pattern appears with greater frequency on pregnancy charts than non-pregnancy charts. There are a couple of factors that may help to explain why this pattern appears with greater frequency on pregnancy charts.
Research on implantation dips-
11% of charts that showed ovulation but did not result in a pregnancy displayed this pattern.
23% of charts that showed ovulation and did result in a pregnancy showed this pattern.
Of the pregnancy charts that showed this pattern, the most likely days for the dip to occur were between 7 and 8 days past ovulation.
The data suggest that this pattern is indeed more likely to result in a pregnancy.
Remember, though, if you have this pattern, it does not necessarily mean that you are pregnant. It is just increasing your probability.
No matter your chart pattern, you can still be pregnant as long
The above information is from http://www.fertilityfriend.com/Faqs/Implantation_dip_study.html