Association between mannan binding protein deficiency and recurrent miscarriage.

The distribution of mannan binding protein (MBP) in blood donor sera was determined by enzyme-linked immunosorbent assay to establish normal concentrations. Abnormally low MBP concentrations were found in 16% (21 out of 135) of female partners and 14% (15 out of 108) of male partners of couples experiencing recurrent miscarriage, compared with < 5% of obstetrically normal controls (P < 0.005). This relationship was even stronger (9.5 versus 1.0%) and more significant (P < 0.002) when only subjects presumed to be homozygous for the mutant allele responsible for MBP deficiency were considered. By immunohistochemistry, MBP could be demonstrated in first trimester placenta. We suggest that low concentrations of MBP within the feto-placental unit increase susceptibility to fetal loss, possibly via an infection-induced placental cytokine imbalance.