[Measurement of fluorescent polarisation in the amniotic fluid to assess fetal lung maturity (author's transl)].

A new method for determining fetal lung maturity is discussed. Molecular mobility can be determined spectrophotometrically by measuring the fluorescent polarisation (FP) in lipid solutions. This method of determining the microviscosity in lipid solutions can now be applied also in the amniotic fluid. Measurement of FP by means of an electro-optical microviscosimeter is proportional to the lipid concentration in the amniotic fluid and is in good correlation with fetal lung maturity. FP was measured between the 17th and 41st weeks of gestation in 147 amniotic fluid samples. During pregnancy the FP value drops significantly from 0.350 to 0.200. A FP value of 0.290 was fixed as the limit value beyond which RDS may be expected to occur. With a limit value of 0.290, the RDS identification probability was calculated at 94%, whereas the calculated probability of RDS was 81% and the exclusion probability of RDS 97%. At the same time, the probabilities, calculated on the parallel determination of the L/S ratio, yielded a slightly more unfavourable result. The drop in the FP level correlates significantly with the increase of the L/S ratio in the investigated amniotic fluid samples (correlation coefficient 0.77). The method, which requires very special equipment, offers many advantages: it is very accurate, simple, well reproducible and can be performed within half an hour at relatively low laboratory cost.