Mannan-binding lectin deficiency is associated with unexplained recurrent miscarriage

Mannan-binding lectin (MBL) is a plasma protein which, upon binding to micr obial carbohydrate structures, elicits activation of the complement system. The level of MBL is genetically determined. It has been reported that the frequency of low plasma levels of MBL is increased in patients with unexpla ined recurrent miscarriages (RM). In the present study plasma MBL levels we re determined in 146 Danish women with RM and 41 of their husbands together with 49 Scottish RM women and 41 of their husbands. In both countries MBL levels were also investigated in a total of 444 controls. Based on the cont rol data, a cut-off MBL level < 50 ng/ml was selected to define MBL deficie ncy. The typical odds ratio for MBL deficiency among female patients in the two populations was 1.68 (95% confidence limits 1.01-2.80, P<0.05) whereas it was 1.57 (95% confidence limits 0.72-3.42, not significant) for the mal e partners of the patients. There was a significant correlation between the frequency of MBL deficiency in RM women and the number of previous miscarr iages (P<0.01), whereas no such correlation was found in the husbands. The results indicate that maternal MBL deficiency is associated with RM. Matern al MBL deficiency might impair the immune defence against microorganisms at the fete-maternal inter-face.