Risk factors for spontaneous abortion in early symptomatic first-trimester pregnancies.

OBJECTIVE: To evaluate the association of an ultimate diagnosis of miscarriage with various clinical symptoms and historical factors in a cohort of women presenting with pain, bleeding, or both in the first trimester of pregnancy.

METHODS: This was a case-control study from a population of women presenting for care with pelvic pain or vaginal bleeding in the first trimester of pregnancy whose diagnoses were not definite upon initial evaluation. Analyses were performed in 2 ways. In one instance cases were defined as women ultimately definitively diagnosed with a miscarriage and controls were defined as women with a pregnancy that did not result in miscarriage (ectopic pregnancy or ongoing intrauterine pregnancy). The second analysis compared women with a miscarriage only to women who had an ongoing intrauterine pregnancy.

RESULTS: A total of 2,026 women were evaluated, with 1,192 ultimately diagnosed with a spontaneous abortion, 367 with ectopic pregnancy, and 467 with a viable intrauterine pregnancy. Although many risk factors were individually associated with miscarriage in preliminary analysis, in the final analysis only extremes in age (< 25 and > 35) and the complaint of bleeding (odds ratio [OR] 7.35, 95% confidence interval[CI] 5.74-9.41) were associated with miscarriage. The complaint of pain (OR 0.72, 95% CI 0.57-0.92), human chorionic gonadotropin (hCG) value greater than 500 (hCG < or = 500 IU/mL compared with hCG 501-2000: OR 0.52, 95% CI 0.39-0.69) and concurrent cervical infection (OR 0.69, 95% CI 0.55-0.88) were negatively associated with miscarriage.

CONCLUSION: Few factors predict miscarriage in women who present with a symptomatic first trimester pregnancy of unknown location. Heavy bleeding was most strongly associated with miscarriage. Concurrent cervical infections should not be overlooked as a cause of bleeding in early pregnancy and were not associated with miscarriage.

LEVEL OF EVIDENCE: II-2.