Objective: To examine birthweight and preterm birth rates in couples with unexplained recurrent miscarriages.
Design: A case control study. Birth data of couples with recurrent miscarriages were obtained from midwife records. Time and sex-matched births from the same records served as controls.
Setting: A Regional Hospital in Denmark.
Subjects: 79 singleborn women with recurrent miscarriages and 60 of their male partners comprised the main study groups. Two control groups comprised 474 female and 360 male singleborn infants who survived day 7 postpartum.
Main outcome measures: Mean birthweight in the two main study groups and in subgroups with histories of 3, 4 and greater than or equal to 5 miscarriages.
Results: The mean birthweight of the women with recurrent miscarriages was 3265 g (SE 70) and in female controls 3414 g (SE 23) (P less than 0.025). The 17 women with five or more miscarriages had a mean birthweight of 2991 g (SD 140) (P less than 0.001 compared with controls). Of the women in the study group 10.8% were born preterm compared with 2.9% of the controls (P = 0.01). The mean birthweight of the male partners in the study group, 3470 g (SE 68), did not differ significantly from that of 3504 g (SE 31) in the male controls (P less than 0.5).
Conclusions: Women suffering unexplained recurrent miscarriages have on average had a significantly lower than normal birthweight themselves, whereas this was not observed in their male partners. This points towards the existence of a birthweight-reducing trait associated with recurrent miscarriages, the trait being manifest only in the woman.