Yes, it is indeed possible for a miscarriage to occur even when the embryo has been identified as euploid, meaning it possesses the correct number of chromosomes.
While preimplantation genetic testing for aneuploidy (PGT-A) is a powerful tool to screen embryos for chromosomal abnormalities before implantation, a euploid result does not guarantee a successful pregnancy or prevent all miscarriages.
Why Euploid Embryos Can Still Miscarry
The misconception that a euploid embryo ensures a live birth is common, but several factors can lead to miscarriage despite a normal chromosomal count:
- Undetected Chromosomal Abnormalities (Mosaicism and Polyploidy):
- Further investigation of euploid embryos that unfortunately resulted in miscarriage has revealed that a notable portion—31.6%—exhibited mosaicism (containing a mix of normal and chromosomally abnormal cells).
- Additionally, 5.2% were found to be polyploid (having extra complete sets of chromosomes, such as three or four sets instead of the usual two).
- This suggests that some chromosomal irregularities might not be detectable during initial screening, especially if the abnormal cells are not sampled during the biopsy process.
- Overall, the presence of chromosomal abnormalities is significantly higher in embryos that miscarry (36.8%) compared to those that lead to live births (15.8%), highlighting that even subtle or previously undetected genetic issues can contribute to pregnancy loss.
- Limitations of PGT-A Biopsy: PGT-A typically involves biopsying a few cells from the trophectoderm (the outer layer of the embryo that will form the placenta). While generally accurate, this small sample might not always perfectly represent the genetic makeup of the entire embryo, particularly the inner cell mass that develops into the fetus.
- Non-Embryonic Factors: Miscarriage can also be caused by issues unrelated to the embryo's genetics. These include, but are not limited to:
- Uterine Abnormalities: Structural problems with the uterus, such as polyps, fibroids, or a septate uterus, can interfere with implantation or embryo development.
- Hormonal Imbalances: Insufficient levels of hormones crucial for sustaining pregnancy, such as progesterone, can lead to miscarriage.
- Immunological Issues: In some cases, the mother's immune system may mistakenly attack the pregnancy.
- Blood Clotting Disorders: Conditions that increase blood clotting can disrupt blood flow to the placenta.
- Infections: Certain infections can pose a risk to the pregnancy.
- Maternal Health Conditions: Uncontrolled chronic conditions like diabetes or thyroid disorders can increase miscarriage risk.
Understanding that a euploid embryo miscarriage can occur helps manage expectations and encourages a comprehensive evaluation of potential contributing factors beyond embryonic chromosomal health.
For more information on the causes of miscarriage, visit reputable health resources like the Mayo Clinic.
