Immunoglobulin G antisperm antibodies and prediction of spontaneous pregnancy.

To investigate the predictive capacity of immunoglobulin G ASA (direct MAR test) for spontaneous ongoing pregnancy in subfertile couples.Prospective cohort study.Nine fertility centers in The Netherlands.Consecutive ovulatory subfertile couples.A basic fertility workup, including a mixed agglutination reaction test for IgG (MAR test) at first semen analysis.Spontaneous conception resulting in ongoing pregnancy.We included 1,794 couples, of which 283 (16%) had a spontaneous ongoing pregnancy within 1 year. When a threshold 50% was used for an abnormal test result, the MAR test was positive in 3% of the couples. In the univariable analysis, a positive MAR test >or=50% reduced, albeit not statistically significant, the probability of spontaneous pregnancy (hazard ratio [HR] 0.76, 95% confidence interval [CI] 0.34 to 1.7). In the multivariable analysis, a positive MAR test >or=50% had no contribution in the prediction of spontaneous pregnancy (HR 0.99, 95% CI 0.40 to 2.4).This large cohort study shows that the MAR test is not able to predict spontaneous pregnancy chances. Its routine use in the basic fertility workup for identification of couples with low spontaneous pregnancy chances is not justified.