The chances of an error with ultrasound are up to 5 percent, says Schaffir. An ultrasound can be between 95 to 99 percent accurate in determining sex, depending on when it's done, how skilled the sonographer is and whether baby is in a position that shows the area between their legs. Mistakes can also be made.

Is it possible for a sonogram to be wrong?

By the midpoint of pregnancy, an ultrasound can give you a pretty good prediction of your baby's sex (if you want to know). But it is possible for the ultrasound prediction to be incorrect, and you've probably heard stories about people who have prepared for the boy they saw on ultrasound who was actually a girl.

Why are ultrasounds inaccurate?

The estimated weight that is calculated is just an estimate based upon the size (or mass) of the baby. But since those extra factors (bone density, etc.) cannot be evaluated with ultrasound, the TRUE weight of the baby cannot be measured with 100% accuracy.