Spontaneous abortion is a common outcome of pregnancy, especially in the first trimester of pregnancy. Defined as delivery prior to 20 weeks of gestation, spontaneous abortion is often an unexpected and traumatic experience for the patient and her family. Spontaneous abortion is discussed in detail in Chap. 9. Briefly, abortion can be considered to fall into one of two categories: complete abortion, which is defined as delivery of all products of conception prior to 20 weeks’ gestation, or incomplete abortion, defined as delivery of some but not all products of conception prior to 20 weeks’ gestation.

In addition to these two categories, first-trimester bleeding can also indicate a possible impending abortion. Uterine bleeding prior to 20 weeks’ gestation without delivery of any products of conception is considered a threatened abortion. Uterine bleeding prior to 20 weeks with cervical dilation but without delivery of products of conception is referred to as an inevitable abortion.

Although spontaneous abortion is common, recurrent pregnancy loss (three or more consecutive abortions prior to 20 weeks’ delivery) is considerably less common, affecting approximately 1 % of all women of childbearing age. In addition to the evaluation and management considerations that pertain to a single episode of spontaneous abortion, recurrent spontaneous abortions require further evaluation and more significant management considerations (see Table 11.1).