WFWW-Implantation Question

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Questions from the reproductivepartners.com bulletin board

Q. When does implantation take place in IVF?

I have had IVF with blastocysts (5 day old embryos) implanted. When the blastocyst is placed in the uterus what stops it from falling out? And when would implantation occur? Immediately? Also, what criteria are used to judge the quality of blastocysts?

A. Embryos are sticky and can adhere to the surface of the uterine lining before they actually implant, which helps prevent them from “falling out.” In addition, we now use a substance in the fluid used to transfer the embryos to make it the same viscosity as fluid in the uterine lining, which prevents migration of the embryos in IVF. That’s so-called “embryo glue,” although it is not really a glue. Despite these measures, the embryos can float around somewhat, and that's why we want activity restricted for 48 hours after an IVF embryo transfer.

Implantation is defined as the process by which an embryo attaches to the uterine wall and penetrates the surface and the circulatory system of the mother. It starts between six to ten days after ovulation in natural conceptions, or egg retrieval in IVF, no matter how and when the embryos reach the uterus. Usually the degree of development of the embryo will determine when the process will actually begin. Most of the time, implantation occurs silently. There are no consistent signs or symptoms associated with it except that it occasionally can result in some vaginal spotting or bleeding which may be mistaken for the start of the next menstrual period.

In IVF, blastocysts are generally graded on the stage of their general development on a one to six scale, and the specific development of what will become the fetus and the placenta on A-B-C scales (A being best). Blastocysts graded at 3AA or higher would generally be considered good quality blastocysts, although this grading level is not required to create a healthy pregnancy. Many healthy babies have been born from embryos which have only reached the stage before blastocyst (morula) after five days of development. Of course none of this is known in a pregnancy conceived by conventional means as we have no idea of what was happening to that embryo, although they would be going through much the same process.

Arthur L. Wisot, M. D.
Reproductive Partners Medical Group, Inc.
Southern California