The development of the fetal penis -: an in utero sonographic evaluation

Objective To establish a nomogram for fetal penile length during gestation. Design A prospective, cross-sectional study of normal singleton pregnancies. Subjects Four hundred and nineteen male fetuses between 14 and 38 weeks were studied. Methods Measurements of fetal penis length were performed by high resolution transvaginal ultrasonography between 14 and 17 weeks of gestation, and by transabdominal ultrasonography beyond 18 weeks of gestation. Results Adequate penile length measurements were obtained in all 419 fetuses. Penile length as a function of gestational age was expressed by the regression equation: (square root) penile length (mm) = 0.277 + 0.121 x gestational age (weeks). The correlation coefficient, r = 0.967 was found to be highly statistically significant (P < 0.0001). The normal mean and the 90% prediction limits were defined. During the study period, we identified three fetuses with abnormalities involving penile development. Using the above reference data range, it has been shown that their penile length was below the lower limit. Conclusions The present data provide a normal range of fetal penile length from early stages of gestation that may allow intrauterine assessment of the development of the male external genitalia.