Fetal phallic growth and penile standards for newborn male infants.

No appreciable difference in size of the fetal clitoris versus the fetal penis was noted until 14 weeks' gestation, which is after the period of masculine differentiation of the external genitals. However, significant differences in the rate of penile and clitoral growth were evident in second trimester fetuses. The majority of the prenatal growth of the penis occurs after 14 weeks gestation at an almost linear rate. The penile stretched length of the full-term infant was 3.5 cm plus or minus 0.7 cm and the diameter was 1.1 cm plus or minus 0.2 cm.