Abortion

The most common complication of pregnancy is spontaneous abortion, which is estimated to occur in 10-15% of pregnancies. Spontaneous abortion can be classified as threatened, inevitable, incomplete, complete, or missed. Spontaneous abortions can further be categorized as sporadic or recurrent (>3 occurrences). By definition, a complete abortion is the expulsion of all products of conception before the 20th week of gestation.

Pathophysiology

Pathophysiology of a spontaneous abortion may be suggested by the timing of miscarriage. Chromosomal defects commonly are seen in spontaneous abortions, especially those that occur during 4-8 weeks' gestation. Genetic etiologies are common in early first-trimester loss but may be seen throughout gestation. Trisomy chromosomes are the most common chromosomal anomaly. Insufficient or excessive hormonal levels usually result in spontaneous abortion before 10 weeks' gestation. Infectious, immunologic, and environmental factors generally are seen in first-trimester pregnancy loss. Anatomic factors usually are associated with second-trimester loss. Factor XIII deficiency and a complete or partial deficiency of fibrinogen are associated with recurrent spontaneous abortions. more