How to determine male or female fetus genitalia in an ultrasound

Updated November 21, 2016

One of the most exciting moments for expectant parents can be finding out their baby-to-be's gender. Ultrasound technology has made it easier to determine a foetus' gender earlier in the pregnancy, but even then, it's impossible for medical staff to be 100 per cent accurate every time. Certain signs, however, can be excellent indicators that the foetus is either male or female.

Go in for an ultrasound at 16 weeks gestation, which is the earliest point at which gender can be determined.

Look for signs in the genital area that may indicate a female foetus. The labia, or outer rim of the vagina, is generally the most noticeable genital sign on an ultrasound. In the genital area, it is indicated by three small lines in a row.

Look for signs in the genital area that may indicate a male foetus. You might see a small protrusion that resembles the head of a snail, indicating the scrotum and penis.

Return for an ultasound, if unsuccessful, at 16 weeks, and again at 20 weeks, and look for these signs. You may just need more time. By 16 weeks gestation, gender can be determined about 85 per cent of the time, according to obstetrician Dr. Michael Applebaum.


Even if you don't notice the presence of either of these known signs, the absence of them could also be an indicator that the foetus belongs to the opposite gender, although you can never be completely certain. Don't fret if you don't see either of these indicators right away. According to Applebaum, it's not only the ultrasound but the foetus itself that makes gender difficult to determine, even for medical professionals. Sometimes the foetus is in a position that makes it difficult to see the genitals. In some cases, gender is unknown until the moment of birth.


In the past, the absence of a penis was taken to indicate a female. This is no longer the case, since the foetus can be positioned a number of different ways. Always be sure to check for the "three lines" of the labia before deciding for sure.

Things You'll Need

  • Ultrasound machine
  • Medical professional to supervise
  • Sample photos of what to look for
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