Penile tumescence in the human fetus at term--a preliminary report

The aim of this study is to reveal whether the penis per se actually becomes tumescent and flaccid, in time sequence, in the human fetus at term. We observed the fetal penis with real-time ultrasonography in 50 male human fetuses at 36-39 weeks' gestation and measured the penile length once at a given time per 1-min epoch for each case during the 60-min window of examination. Thirty-eight were excluded due to a lack of continuous ultrasound visualization of the penis. Penile length changes were statistically analyzed for the remaining 12 fetuses using the 'least median of squares regression'. Penile length was seen to be significantly stratified into two groups: 22.5% at tumescence (group median = 20.8 mm) and 77.5% at flaccidity (group median = 16.0 mm). Penile tumescence was found to occur at the following frequency during the given observation period: once in 41.7%, twice in 50.0% and three times in 8.3% with durations ranging from 5 to 17 min. These findings indicate penile tumescence exists in the term fetus. The frequency and duration of penile tumescence are in good correlation with neonates.