Spontaneous Abortion

SPONTANEOUS ABORTION

Abortion is the expulsion of the fetus prior to 20 weeks ofgestation. Spontaneous abortion (miscarriage) occurs in the absence of intervention. An incidence of recognized spontaneous abortion of 15% to 25% is commonly cited, with approximately 80% occurring during the first 12 weeks of pregnancy. Approximately 50% of early spontaneous abortions are attributed to chromosomal abnormalities, most of which are trisomy.

Compared with first-trimester abortions, second-trimester abortions are less likely to be caused by chromo-somal abnormalities and more likely to be caused by ma-ternal systemic disease, abnormal placentation, or other anatomic considerations. This difference is clinically signif-icant, because these conditions often can be treated and re-current abortions can thereby potentially be prevented.