What Causes Pre-Implantation Pregnancy Loss in IVF?
Why Is the Pregnancy Lost?
In vitro fertilization is a blessing for many couples who are unable to conceive a pregnancy without assistance. However, even when the embryo is established prior to implantation, often a pregnancy is lost. The unfortunate aspect of IVF is that there are no guarantees of having a baby, even if pregnancy is conceived. The emotional and physical toll on a couple can be disheartening and difficult at best.
There are really only two reasons for pre-implantation pregnancy in IVF - either there is something wrong with the embryo itself that does not allow it to implant, or there is something in the environment of the uterus that doesn't allow the embryo to implant.
What Causes the Problems with the Embryo?
When the problem is with the embryo it is commonly due to abnormal chromosome numbers, called aneuploidy. In 30 to 90 percent of embryos with chromosomal abnormalities, the problem (depending upon the age of the mother) is with the egg. The reason the egg is complicit most of the time is because it is the egg that has the job of accepting the DNA from the sperm then mixing the genes to create a new and unique person. The age of the egg determines in large part how chromosomally normal it will be. For women under the age of 30, normal ranges are about 50 percent. However, by the age of 45, the normal range for eggs drops to five percent. Fragmented DNA from the sperm has also been associated with poor embryo quality and failure to implant.
How Do Uterine Problems Affect Loss?
Uterine problems take the form of structural, hormonal or immunological difficulties.
· Structural or anatomical abnormalities within the uterus can make it mechanically impossible for implantation to occur. They act like an IUD by prohibiting the implantation of an embryo and take the form of:
a) Endometrial polyps, which are benign growths in the uterine lining that protrude into the uterine cavity.
b) Submucous fibroids, which are also benign tumors in the uterine wall that protrude into the uterine cavity.
c) Uterine adhesions inside the uterine cavity.
· Hormonal difficulties can be problematic. Since the levels of estrogen and progesterone are very carefully controlled during IVF procedures, it is unusual for hormones to be a reason for recurrent pregnancy loss within IVF. However, mutations that affect the progesterone receptors have been connected to recurrent implantation failure.
· Immunological problems are definitely causes of recurrent failed implantation and pre-implantation pregnancy loss. It is necessary for the uterus to accept and tolerate the implanted embryo. Both the embryo and the maternal uterine environment communicate with each other through proteins found in the cells of the uterine lining (cytokines). If there is not correct communication to the embryo from the cytokines in the uterus or if the uterus does not recognize the signals of the embryo, then there will likely be a problem with adhesion and implantation.
Diagnosing the Problems
In order to treat this condition effectively, it is important that a correct diagnosis is established. Since pre-implantation pregnancy loss occurs after the egg is fertilized and before it is implanted, it can be the result of problems with the egg or with the sperm. If it is the egg, the problem can be diminished ovarian reserve or premature ovarian failure. Diagnostic testing for these conditions includes follicle stimulating hormone (FSH) testing and testing for antiovarian antibodies (AOA).
When there are sperm problems that haven't been detected with standard semen analysis, then other, more extensive testing can be done.
· Sperm DNA Integrity assay (SDIa) measures DNA damage in sperm. Standard semen analysis which includes sperm concentration, motility or morphology, does not include the markers of sperm quality used to predict pregnancy outcome in their parameters. An SDIa is the test used to get those results.
· Y chromosome microdeletion assay discovers the genetic condition of microdeletions in the Y chromosome that results in no sperm or very low sperm counts. The importance in identifying men with Y chromosome deletions is because the deletions can be transmitted by ICSI injections.
Post a comment