At around 19 weeks it can be possible to tell the sex of the baby at this scan, but it is not always. The baby may not be in a favourable position to determine the gender. However, if you would like to know the gender of your baby please inform your sonographer at the beginning of your ultrasound. Determining the sex of the baby is not always an easy job as we are depending on the baby to be in a position that allows us to visualise the genital area and the baby does not always oblige.