What defines a spontaneous abortion?

A spontaneous abortion, often referred to as a miscarriage, is defined as the natural termination of a pregnancy before 20 weeks of gestation. This typically occurs without any medical intervention or intent. The majority of spontaneous abortions happen in the first trimester, and they can be caused by a variety of factors such as chromosomal abnormalities, hormonal imbalances, or anatomical issues with the uterus.

Termination of pregnancy after 20 weeks, as outlined in one of the other options, does not fall under the definition of spontaneous abortion; instead, it may be categorized as a stillbirth if the fetus has died after viability but before delivery. Likewise, a termination due to medical complications or an induced abortion involves either medical intervention or specific circumstances that do not align with the concept of a spontaneous abortion. Thus, the defining characteristic of a spontaneous abortion is its occurrence naturally before the 20-week mark.