When is the best time to check a pregnancy test if you have regular cycles and are trying to get pregnant? Is it true the earlier the test turns positive the less likely it is to have a miscarriage? " Anon

Many women who are trying to conceive want to learn when ovulation and implantation occur and what are usual miscarriage or pregnancy loss rates. Quite often the numbers women are given are based on averages, theoretical numbers and sometimes just plain guesses because it is such a difficult topic to scientifically investigate. New data comes available periodically but it is not always promptly and widely disseminated even on the Net. When does implantation take place?

One such relatively recent study tells us that implantation does not always take place on day 7 after ovulation. In fact it very rarely does. This study accurately determined the day of implantation by very sensitive pregnancy test (HCG) measurement compared to ovulation.

HCG hormone starts being produced when the pregnancy implants into the uterine lining. The findings in normal women trying to conceive included:

• first appearance of HCG (implantation) occurred 6-12 days after ovulation

• 84% of the pregnancies implanted on days 8-10 after ovulation

• early pregnancy loss increased with later implantation - implantation early pregnancy loss rate o 13% by day 9,
  o 26% on day 10,
  o 52% on day 11 &
  o 86% on day 12 or more

Overall the total pregnancy loss up to 6 weeks was 25%. Now that seems very high to most people but keep in mind many of these pregnancy losses occurred so early that women often were not aware they were even pregnant. The normal early pregnancy loss rate that most women know about is 15-18% of clinically recognized pregnancies so almost 40% of all pregnancy loss is unrecognized.