Lupus anticoagulants, anticardiolipin antibodies, and fetal loss. A case-control study.

BACKGROUND: Lupus anticoagulants and anticardiolipin antibodies are antiphospholipid antibodies that have been associated with fetal loss, but they have not been shown unequivocally to be a risk factor for this event.
METHODS: To estimate the risk of fetal loss in association with these antibodies, we conducted a hospital-based case-control study of 331 women with spontaneous abortion or fetal death (case patients) and 993 controls. The subjects were included in the study only if they reported that they had had no previous spontaneous fetal loss. Each control was a pregnant woman who, in the same period of pregnancy as a case patient, had not had a fetal loss. Lupus anticoagulants were identified in blood samples through a series of coagulation tests, and IgG anticardiolipins by an enzyme-linked immunosorbent assay. Each subject was interviewed in person to obtain information on potential confounding variables, such as sociodemographic characteristics and medical conditions.
RESULTS: Lupus anticoagulants were found in blood from 17 case patients (5.1 percent) and 38 controls (3.8 percent). The crude odds ratio for the association between lupus anticoagulants and fetal loss was 1.36 (95 percent confidence interval, 0.75 to 2.43); the odds ratio adjusted for confounders was 1.42 (95 percent confidence interval, 0.72 to 2.80). An IgG anticardiolipin level of 5 units or more was found in 4 case patients (1.2 percent) and 15 controls (1.5 percent). The crude and adjusted odds ratios for fetal loss were 0.80 (95 percent confidence interval, 0.26 to 2.41) and 1.28 (95 percent confidence interval, 0.38 to 4.21), respectively.
CONCLUSIONS: There is not apparent justification for considering lupus anticoagulants or IgG anticardiolipins to be risk factors for fetal loss among women who present with spontaneous abortion or fetal death and have had no previous spontaneous fetal loss.