Miscarriage rates following IVF are similar compared to pregnancies from natural conception. The chance of embryo loss after a positive pregnancy test is 15-17% of biochemical pregnancies, as compared to 12-15% after natural conception. In 65-70% of cases early pregnancy loss is a result of chromosome abnormalities of the embryo.
Increased age of the woman is another important factor, among others, responsible for this unfortunate result. Miscarriages can happen in the 1st or 2nd semester before the 24th week and can be attributed to the fetus, the mother, and more rarely the father. Maternal reasons include age, infections, systemic diseases, endocrine disorders and immunological factors, as well as lifestyle (smoking, alcohol, drugs). Also uterine abnormalities (congenital abnormalities, endometrial adhesions, fibroids) and insufficiency of the cervix.
Usually the causes are related to physical malfunctions or chromosomal abnormalities of the embryo, causes that are not possible to predict during the process of IVF. We remind you that the quality of embryos transferred is defined using only morphological criteria, which are not able to depict possible chromosomal abnormalities, with the exception of PGD (see previous section).
The chance of a clinical pregnancy not resulting in a live birth is small and statistically similar to natural conception. From the stage of ongoing pregnancy until birth the chance of embryo loss is estimated at around 1%.
The most common types of pregnancy loss are:
- Automatic extrusion
- Regression
- Ectopic pregnancy
- Premature labour with the birth of a live or dead infant.
However, with close monitoring, combined with technological advances of neonatal unitsm this percentage is now very low.
