Does Late Implantation Cause Miscarriage?

The timing of when a fertilized egg implants in the uterus affects the chances of whether it can develop successfully or there could be a miscarriage. Implanting too early or too late may mean the uterine lining and the levels of hormones are not the best for supporting the embryo. While late implantation can be a factor in pregnancy loss, it is one over which you have no control.

Ovulation and Implantation Window

When you ovulate, halfway through your menstrual cycle an egg is released from your ovary into a fallopian tube. The egg, on average, has 24 hours to be fertilized before it is no longer viable. During conception, the egg is fertilized in the fallopian tube and then travels along the fallopian tube to make its way into the uterus. Once in the uterus, the egg implants itself into the lining (endometrium) of the uterus. From start to finish, implantation takes about 48 hours.

The journey from conception to implantation can take anywhere from six to 12 days. Implantation that occurs on the late end of the spectrum is known as late implantation.

The spot where the embryo attaches itself inside of the endometrium can disrupt some blood vessels, which may cause some light bleeding anywhere from five to 10 days after conception, but before your period would typically occur. However, not everyone bleeds. Lack of bleeding doesn't mean you aren't pregnant or that you don't have late implantation.

Late Implantation and the Risk of Miscarriage

Several studies have found a higher risk of miscarriage in pregnancies where implantation occurs more than eight to 10 days after ovulation. A classic study published in the New England Journal of Medicine (NEJM) found that the likelihood of miscarriage increased significantly with every day of late implantation after day nine. On the ninth day, the likelihood of miscarriage was 13 percent, on day 10 it was 26 percent, and on day 11 the rate was 52 percent. Any later than 11 days and the risk of miscarriage increased to 82 percent. What exactly these findings mean, however, is debatable.

Late implantation, by itself, is unlikely to be a direct cause of miscarriage. Embryos with chromosomal abnormalities, like trisomies or translocations, are more likely to miscarry. If an embryo has a chromosomal anomaly, the abnormal genetic material may also cause the embryo to implant later than usual. Another theory is that some factor in the uterine lining could cause problems during implantation and that this could lead to miscarriage, but researchers are still studying the matter.

Causes of Late Implantation

A study of late implantation found that current smoking was a risk factor for late implantation. If you are trying to become pregnant, this is one of many reasons to quit smoking. But other than that, the timing of implantation isn't under anyone's control. Beyond having an in vitro fertilization procedure that would place the fertilized egg directly in your uterus, there is no way to speed up an egg's trip down the fallopian tubes into the uterus. And once the egg is in the uterus, there is no way to force it to embed in the uterine lining.

If you have had several miscarriages, it is unlikely that late implantation is the sole cause.

There is no evidence that late implantation by itself causes miscarriage. However, the later the egg implants the more likely miscarriage is to occur. If you have menstrual irregularities or if you have been struggling to conceive, talk to your doctor to see if there are any problems potentially interfering with your ability to get pregnant. Further testing may uncover the reason your embryos are implanting later than what is considered normal.

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