Amniotic fluid beta 2-microglobulin (beta 2-m) as an index of fetal maturity.

Amniotic fluid beta 2 microglobulin (beta 2-m) levels were measured by radioimmunoassay in 78 pregnant women between the 14th and the 42nd week of gestation. 62 were healthy subjects, while eight were affected by EPH gestosis, seven by diabetes (cl. B-F) associated with Rh immunization in one case, one by hydramnios. There was no significant correlation either between beta 2-m and creatinine (n = 18), or between beta 2-m and lecithin sphingomyelin ratio (L/S) (n = 16), although low concentrations of beta 2-m were usually observed after the 35th week of gestation. It is noteworthy that only in one case out of seven with amniotic levels less than 5 microgram/ml L/S ratio was less than 2.