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Miscarriage is devastating for expectant parents, and understanding the prognostic factors that are associated with recurrent miscarriage is vital for counseling patients as well as uncovering underlying pathophysiology. History of a firstborn male child has been proposed as a risk factor for secondary recurrent miscarriage. In a new study, investigators analyzed data from two cohorts of women referred to the Danish recurrent miscarriage clinic. Data were collected retrospectively from a cohort of 175 women and prospectively from a later, separate cohort of 130 women; both cohorts were combined for this analysis. All women had histories of at least three consecutive intrauterine pregnancy losses before 22 weeks’ gestation, with previous live births.
The two cohorts had similar median maternal ages and overall live-birth rates (62% vs. 71%; P=0.13). In the combined cohorts, significantly more women had firstborn boys (60%) than firstborn girls (40%). Regression analysis of the 240 women who conceived after referral showed that having delivered firstborn males negatively affected the likelihood of having subsequent successful deliveries (odds ratio, 0.37; 95% confidence interval, 0.2–0.7). Higher numbers of prior miscarriages also predicted lower likelihood of successful delivery (OR, 0.71; 95% CI, 0.6–0.9, compared with women with histories of 1 fewer previous miscarriage). Maternal age and history of intravenous immunoglobulin treatment or of changing sexual partners between pregnancies were not significant predictors of miscarriage.
Nielsen HS et al. A firstborn boy is suggestive of a strong prognostic factor in secondary recurrent miscarriage: A confirmatory study. Fertil Steril 2008 Apr; 89:907.
Comment
The difficult clinical circumstances of miscarriage, especially for women who suffer repeated episodes, require a better understanding of why these episodes occur. The authors posit that maternal immunization against male-specific minor histocompatibility antigens in a first pregnancy might play a role; also, they correctly suggest that laboratory studies must complement clinical observational studies to elucidate the pathology of secondary recurrent miscarriage.