Are miscarriages related to an abnormal number of chromosomes in the embryo?

This study looked at whether couples who had repeated miscarriages or lack of implantation were more likely to have embryos with an unusual number of chromosomes (aneuploidy). It found that couples with repeated past miscarriages were more likely to have aneuploid embryos.

When eggs and sperm form, pairs of chromosomes are separated. Chromosomes carry the genetic information. Sometimes this process happens incorrectly, causing an unusual number of chromosomes (aneuploidy). In an aneuploid embryo, proteins are made in the wrong amounts and the embryo does not develop normally. Most aneuploidies cause death in infancy.

Implantation is the process when an embryo attaches to the womb. Over a third of fertilized embryos do not survive past when the woman expects her period. An abnormal embryo is less likely to successfully implant.

Recurrent early miscarriage can contribute to infertility. One treatment option for infertility is in vitro fertilization (IVF). This is where eggs are collected and fertilized in the lab. For couples with repeated miscarriage, preimplantation genetic testing for aneuploidies (PGT-A) is an option prior to IVF. It is unclear how PGT-A testing affects IVF treatment for couples with repeat lack of implantation or miscarriage.

This study included 792 couples with repeated early miscarriages or a lack of implantation during IVF. They underwent egg collection and fertilization using ISCI (intracytoplasmic sperm injection). The embryos were screened with PGT-A. 40.87% of embryos had aneuploidy.

More aneuploid embryos were associated with a higher likelihood of having 4 or more previous IVF failures (42.86% vs 33.05%). Couples with two or more previous pregnancy losses had a trend toward more aneuploid embryos (43.84% vs 33.05%). Couples with four or more early miscarriages were more likely to have an aneuploid embryo.

932 embryos were transferred. Past lack of implantation did not make implantation or live birth less likely. Women with a past late miscarriage were 3.16 times more likely to have a miscarriage.

This study found that women with previous lack of implantation and early miscarriage were more likely to have aneuploid embryos. When only normal embryos were implanted, couples with past lack of implantation did not have lower implantation rates.

There are multiple factors which may influence implantation and miscarriage. Aneuploidy is only one factor.