Time of implantation of the conceptus and loss of pregnancy

BACKGROUND: Implantation of the conceptus is a key step in pregnancy, but little is known about the time of implantation or the relation between the time of implantation and the outcome of pregnancy.

METHODS: We collected daily urine samples for up to six months from 221 women attempting to conceive after ceasing to use contraception. Ovulation was identified on the basis of the ratio of urinary estrogen metabolites to progesterone metabolites, which changes rapidly with luteinization of the ovarian follicle. The time of implantation was defined by the appearance of chorionic gonadotropin in maternal urine.

RESULTS: There were 199 conceptions, for 95 percent of which (189) we had sufficient data for analysis. Of these 189 pregnancies, 141 (75 percent) lasted at least six weeks past the last menstrual period, and the remaining 48 pregnancies (25 percent) ended in early loss. Among the pregnancies that lasted six weeks or more, the first appearance of chorionic gonadotropin occurred 6 to 12 days after ovulation; 118 women (84 percent) had implantation on day 8, 9, or 10. The risk of early pregnancy loss increased with later implantation (P<0.001). Among the 102 conceptuses that implanted by the ninth day, 13 percent ended in early loss. This proportion rose to 26 percent with implantation on day 10, to 52 percent on day 11, and to 82 percent after day 11.

CONCLUSIONS: In most successful human pregnancies, the conceptus implants 8 to 10 days after ovulation. The risk of early pregnancy loss increases with later implantation.



Dr. Lessey suggested I look at this study and I find it to be particularly interesting.  It puts some scientific data behind something I have suspected.  You see, with each of my losses, I have had later implantations (gotten a positive pregnancy test anywhere from 10-13 days past ovulation.)  With Ethan I got a positive pregnancy test at 8 days past ovulation (and if I had used a sensitive enough test, would have gotten a positive result on day 7, since my betas were 79 the morning of 7DPO.)  More food for thought.


One thought on “Time of implantation of the conceptus and loss of pregnancy

  1. solymar says:

    One thing to keep in mind is that that study was looking at extremely low levels of HCG that can’t be picked up by a pee stick or normal blood test that most of us are familiar with. So even though they picked up HCG early, most women won’t show a positive line on a pee stick at 8 DPO. If you look at the stats for when a positive shows up for women that are later confirmed pregnant, 65% of women don’t even have a “very faint positive” at 8DPO. The methods used in this study were more sensitive than we have access to. However, it does clearly show that if you don’t get a positive test on the earlier side (a couple days?? before your missed period) you are more likely to have a miscarriage. They did not correlate their results with when a line showed up on a pee stick so it’s hard to say what day a BFP suggests a health/healthier pregnancy. I will say that I’ve had 3 chemical pregnancies now, all in a row the last 3 months, and only 1 of them was a delayed positive (14DPO). I’ve had 3 kids, my only pregnancies before these 3 chemicals, and I was always able to pick up those pregnancies by ~10-11DPO. I don’t think I ever tested earlier. 2/3 of these chemical pregnancies gave me very faint positive lines on 9 and 10 DPO, and the 3rd was on 14 DPO. So the first 2 listed I thought were viable. I used progesterone on my most recent cycle, where I got a very faint positive on 10DPO and although I got the highest initial HCG for the first test (60) on 13 DPO (the average for that day is 50 so 60 is good), the second was down to 55 2 days later so I am loosing it anyways.

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