Final answer:
The number of pregnancies ending in therapeutic or spontaneous abortion before 20 weeks of gestation varies. Miscarriage is a spontaneous termination of pregnancy, while abortion is a voluntary termination of pregnancy. The reasons for both can vary.
Step-by-step explanation:
The number of pregnancies ending in a therapeutic or spontaneous abortion (miscarriage) before 20 weeks of gestation varies. Spontaneous termination of pregnancy, also known as a miscarriage, typically occurs very early in the pregnancy, usually within the first few weeks, when the fetus cannot develop properly. On the other hand, voluntary termination of pregnancy, known as an abortion, can be performed for various reasons, including medical necessity or personal choice.