Is recurrent miscarriage genetic?

Often, though usually not in the way people assume. The most common genetic cause is a chromosome error in the pregnancy itself — a random event, not inherited from either parent. ASRM (2026) states that approximately 50 to 60% of first-trimester miscarriages are due to embryonic aneuploidy, and the rate rises with maternal age: around 50% of tested miscarriages in women under 35, and 75% in women over 40. These are almost always sporadic. They do not recur because of anything either parent carries. A less common cause is an inherited structural rearrangement, such as a balanced translocation in one partner. This accounts for a small percentage of couples with recurrent loss. Something counter-intuitive but important: compared with women who have had an isolated miscarriage, women with recurrent loss have a HIGHER likelihood of euploid miscarriage — that is, losses where the chromosomes were normal — and that likelihood increases with the number of losses. So repeated miscarriage tends to select for losses that are not explained by chromosome errors, which is precisely why testing the miscarriage tissue is informative. ASRM now recommends array-based chromosome analysis of miscarriage tissue as the first step in evaluation, offered at the second miscarriage. If the loss was aneuploid, that explains it and avoids an expensive workup. If it shows an unbalanced rearrangement, parental karyotyping follows. And the most important thing to hear: 50 to 80% of couples with unexplained recurrent loss have a successful subsequent pregnancy with no specific treatment.