Implantation Timing

[Jaimee]

The more I hang out around this forum the more curious I have become about implantation- timing, symptoms, etc.  I keep reading and reiterating in my posts that implantation occurs between 6 and 12 DPO.  But there are always a few women that say they had earlier implantation b/c of the symptoms they experienced (e.g. cramping, bleeding/spotting, etc.).  I was beginning to wonder if my information was totally accurate or if implantation earlier than 6 days is even biologically possible.  If the latter is in fact true, it would suggest that spotting/bleeding earlier than 6 DPO (assuming ovulation was confirmed correctly and the possible 3 day ovulation window was account for) would need to have a different cause- like general hormonal fluctuations or fluctuations associated with ovulation, irritated cervix, etc. 

So I did a bit of PubMed digging and found this article: http://www.ncbi.nlm.nih.gov/pubmed/10362823 stating once again that implantation occurs between 6 and 12 DPO and 84% of the time occurs between 8 and 10 DPO.  It also has some interesting stats about early pregnancy loss based on implantation timing.

At any rate, I am wondering if any of you have other articles or further information you could share about implantation timing and symptoms.

[Jaimee]

Here's the full text link to the full article posted above: http://www.nejm.org/doi/full/10.1056/NEJM199906103402304#t=articleTop

It has further information about their methods and previous implantation studies. The researchers concluded that error in their measurements would result in a narrower window of implantation timing, not wider.  Previous studies indicated windows of 6 or 7-13 DPO and 8-14 DPO.  But these studies involved women undergoing infertility treatments and unhealthy zygotes tend to develop slower and have slower implantation, which more often results in early m/c.   Even so, you can see that the results did not indicate earlier implantation was possible, only later.

[ISISandOSIRIS]

Interesting article, thanks for the info.  I have to say, I personally think some women who claim to have pregnancy symptoms almost immediately may simply be hypersensitive to their bodily functions and a confirmation bias occurs in that they believe that if they are actually pregnant, that those were, in fact, early pregnancy symptoms.  I think this because there were SO MANY times I thought I was pregnant early on because I felt like I was peeing a lot, had random cramping, a spot of blood (which was probably an irritated cervix), felt a dizzy spell, etc... only to NOT be pregnant.  If I WERE actually pregnant, I would have looked back on those symptoms and have thought, "yup, I had very early pregnancy symptoms," when in reality, I was simply hypersensitive to normal things and read deeper into symptoms that had nothing to do with pregnancy. 

[Jaimee]

I agree.  So when I give advice to people I feel like I want to give accurate facts and "likelihoods" (from an article like this for example) instead of, as you said, "confirmation-biased-symptoms" that I was definitely paying more attention to when actively TTC vs. when I had my two oops pregnancies and didn't know until three weeks later.  I also think that when you get a large group of women together that are TTC you're going to get more stories of super rare occurrences and a lot more throwing around of commonly heard TTC terms like implantation spotting, implantation dip, triphasic chart, etc. even though they really aren't that common.

[MunchiesMom]

Interesting! Is this saying tha in 221 women, 199 got pregnant in the 6 month timeframe? If I'm reading it right those are great odds!

[MunchiesMom]

"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."

It is sad to think about how often women miscarry and never even know it. I was several days late last month but always had a BFN and I'm still convinced a little bean attached but couldn't hold on long enough for any measureable HcG.

"Among the pregnancies that lasted 6 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)."

Does later implantation have any correlation to lower HcG levels and one not being able to detect a pregnancy well after the missed AF date? Could one make any connection between viable pregnancies and later BFPs?

Interesting stuff!

[RavenStar]

Thanks for sharing this article, Jaimee.  I've been pondering these same things recently.  I really do think that a lot of the "early signs" are due to post ovulation.  ISISandOSIRIS, I have been in that situation many times as well.  Where I'm looking at all of my "signs", thinking I'm pregnant, when I'm not.  Or as you say, MunchiesMom, maybe sometimes we are pregnant and have an early loss.

This is why I'm trying hard not to test this cycle and just wait to see if my period comes.  It's such a bummer when I test and it's negative.  I'm trying to wait until farther into next week to test.  We'll see!

[ISISandOSIRIS]

I always set a date in my mind that I'll test, which is a day or so past the last possible day I could get AF.  I don't see the point of testing sooner because if it's a BFN I'd trick myself into thinking I tested too early and if it's a BFP I'll find out soon enough! Good luck Raven, I hope you get your BFP soon.

I agree munchie, those were great odds and it got me a little depressed to read!  I suppose the researchers really made sure they found couples with absolutely no fertility problems.  221 isn't that large of a sample, so they probably had pretty strict guidelines.

[TenzinsMama]

IandO, I am completely on the same page as you on the testing part... It really wasn't until I found this forum a couple of months ago that I realized that people were testing so many days before AF is due, and that there were cheap HPTs to get so it doesn't run you into too much money doing it.  I have been tempted to test early sometimes, but I always remember that our fertility clinic advises that after an IUI you should wait until 17 days afterwards to test... so I've always had it in my mind that implantation could happen on the later side, and I've not wanted to have the disappointment of seeing a bfn.  Also, I think I would be so, so difficult for me to get a bfp early on, only it to turn out to be a chemical.  Right now, where my head is at, I would rather not know this and be spared the grief-- getting AF is bad enough.  Although I know some people would be say that the one good thing coming out of it is that they know they can conceive at all.  But for me, it seems there are so many things that factor into it after implantation, that I would feel better about getting a bfp once AF was good and late-- it seems that it is another hurdle that I would have gotten over, and I can allow myself to feel more hopeful then.  I guess what I am saying is that if I was going to have a chemical, the consolation in it for me would be far outweighed by the grief I would experience. 

Raven, I hope you receive your good news next week!

[MunchiesMom]

I was surprised such a lage portion of the sample got pregnant in 6 months. From what I understand there's only a 20% chance you'll get pregnant in a given cycle (% depending on age and other factors). You see the same ladies on message boards with BFNs month after month... it is hard to conceive when you're trying!

If the 20% is correct, statisicall should it take about four cycles of trying to conceive?

With DS I fell into the minority... it took us a year to conceive and the RE was already calling it unexplained infertility. Knowing the stress just four months can bring, I'm hoping to conceive quickly this time around.

[TenzinsMama]

MunchiesMom, not sure in answer to your pondering... however, when I posed the same kind of question to my DH awhile back, he told me that the % isn't cumulative.  It's the same each month.  I 'got it' when he explained it to me, and I believe that what he was saying makes sense, but it's hard to repeat back the same way he explained it to me.  The reason it came up for us, this discussion, was that we were talking about possibly having to do Clomid and IUI-- and he said that we had the same % chance each time (of course, taking into account my age, our fertility diagnosis, and the overeall average success rate of that procedure at our clinic-- our chance is much less than that), and each consecutive IUI didn't increase the % but rather each one gave us more opportunity to 'roll the die'.  So if you apply that to regular BD'ing, I would guess that just means the more months you try, it's bound to happen that you will eventually conceive, barring any major issues of course.  Some are fortunate that they fall into the 'sooner' rather than 'later' category.  It frustrates me to no end, though, that a person can have 'perfect' O, clockwork cycles, excellent timing with BDing, etc and not achieve a pregnancy-- and be told they have unexplained infertility-- science has come along way, but they can't pinpoint everything about conception... in the end, maybe a person needs a little luck on their side, too.  I don't know if I'm putting correct info down here, so it would be interesting if others join in the discussion...

[MOMMYSINCE2008]

I REALLY LOVED READING THIS! THANKS FOR THE INFO! I LOVED IT! THANKS SO MUCH!

[Jaimee]

Originally Posted by MunchiesMom 

Does later implantation have any correlation to lower HcG levels and one not being able to detect a pregnancy well after the missed AF date? Could one make any connection between viable pregnancies and later BFPs?
 

The embryo does not start producing hCG until it implants.  So the later implantation occurs, the less time there is for hCG levels to rise and signal the corpus luteum to remain before it starts to disintegrate, progesterone plummets, and the uterine lining is shed.  If levels are lower, you may not get a BFP- especially on a less sensitive test- prior to the time of expected AF.  But if the latest implantion is about 12 DPO (though 13 and 14 DPO have been recorded in previous studies) then measureable hCG should build up high enough within a couple of days of that... say 15-17 DPO.  Would you consider that "well after" missed AF?  I guess I wouldn't.  It seems more likely in cases of viable pregnancy and delayed BFP that the woman may not metabolize the hCG into her urine as quickly as others. There was also a brief mention in the article that less viable embryos may produce less hCG and take longer to implant:

Pregnancies with late-implanting conceptuses may fail for several reasons. The receptivity of the endometrium decreases during the late luteal phase,1,2 and the corpus luteum is less responsive to chorionic gonadotropin by 11 or 12 days after ovulation.30 Factors intrinsic to the zygote could also be at work. Unhealthy zygotes may develop more slowly, or implantation may be abnormal,31 resulting in later and weaker production of chorionic gonadotropin.32 To the degree that imperfect embryos develop or are implanted more slowly, a limited window of receptivity may provide a gating mechanism that helps screen out impaired embryos.

Originally Posted by TenzinsMama 

... he told me that the % isn't cumulative.  It's the same each month. 

I was going to say this as well.  Each month you have the same probability of conceiving- based on statistics.  However, each cycle is not identical.  A woman can have more fertile and less fertile cycles.  Her chance of conceiving (assuming equally well timed BD) would be higher during those more fertile cycles.  Higher fertility could include more fertile cervical fluid, better timed fertile CF with O, a slightly longer LP, etc. 

Furthermore, when talking statistics there is a difference between your chance that particular cycle and your chances over several cycles.  For example, your chance your first child is a boy is 50%.  Your chance that your second child is a boy is also 50%.  But if you were to calculate your chances ahead of time of having two boys it would be 25% (0.5 x 0.5).  Likewise (assuming the 20% statisitic is correct) your chance of not conceiving your first cycle is 80%.  Same with your second cycle.  But if you were to calculate your chances of NOT conceiving the first two cycles ahead of time it would be 64% (0.8 x 0.8).   Three cycles in a row: 51.2%.  Six cycles in a row: 26.2%.  But this only works when calculating ahead of time.   Each time you don't conceive, that cycle becomes a 100% chance of not conceiving and that means you're back to 80% chance of not conceiving the next cycle.  At least that's what I remember from my statistics class...