At what gestational age can the sex of the baby be determined through the appearance of external genitalia?

At around 12 weeks of gestation, the external genitalia of the fetus begin to visibly differentiate into male or female when assessed through ultrasound imaging. This is due to the development of the genital tubercle, which becomes more defined and can be identified as either a penis or clitoris.

Prior to 12 weeks, while the fetus is developing rapidly, the external genitalia are not yet sufficiently developed for accurate determination of sex. At 8 weeks, the sexual differentiation processes are just beginning, and at 10 weeks, the external features remain in an early stage where they cannot be reliably differentiated. By 14 weeks, the genitalia are more clearly defined but since the question asks for the earliest time at which sex determination can be made, 12 weeks is the correct answer.