[Squalene-cholesterol ratio in the amniotic fluid and gestational age: changes in the threshold in relation to the preparation of the sample].

The squalene/cholesterol ratio in pellets prepared from amniotic fluid is closely correlated to the gestation age and shows a marked increase in the 39th week of pregnancy. However, the absolute value of the squalene/cholesterol ratio may very considerably in relation to the process used to prepare the sample. The washing of the sedimentary cells seems to be critical point in this procedure; therefore, if it is not correctly standardized, erroneous result may be obtained.