[Ultrasonic detection of fetal vernix in amniotic fluid as and index to fetal maturity].

The relationship between ultrasonographic detection of fetal vernix and visual assessment of amniotic fluid (AF) and fetal pulmonary maturity evaluated by the "shake test" was studied in 73 high-risk patients undergoing amniocentesis for obstetrical indications. The AF was classified as type I, type II, and type III, depending on the subjective amount of vernix detected. Ultrasound predicted correctly 7 out of 11 cases of type I AF (64%), 14 out of 22 cases of type II AF (64%), and 38 out of 40 cases of type III AF (95%). When ultrasonography detected type I AF the "shake test" was negative in all cases, whereas if type II or type III were found, the "shake test" was positive in 40% and 86%, respectively. Our results suggest that sonographic detection of type I AF is associated with immaturity, thus amniocentesis should be avoided in such cases. Conversely, if a type III AF is detected a mature fetus is found in almost 90% of the cases. The observation of AF detecting fetal vernix during third trimester sonography is a simple manoeuver that can help to avoid the use of amniocentesis, an invasive procedure associated with some serious fetal and maternal complications.