“…Spontaneous abortion was defined as any unplanned fetal loss before 20 weeks of gestation in 16 studies 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 22 weeks in 1 study (32), and 24 weeks in 1 study (33). Fetal death was defined as any unplanned fetal loss at or after 20 weeks of gestation in 16 studies 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 22 weeks in 1 study (32), and 24 weeks in 1 study (33). To avoid misclassification, we used the definition provided by each individual study.…”