What is the biparietal diameter and above which is more likely to be a boy? When pregnant women undergo prenatal check-ups, a very important indicator is the biparietal diameter of the fetus. So, what is the biparietal diameter and above which are the chances of having a boy? This is a question that many expectant mothers are very concerned about. Below we will elaborate on it from the following four aspects. 1. What is biparietal diameter? Biparietal diameter refers to the length of the transverse diameter of the fetal head, that is, it is determined by measuring the width between the two sides of the fetal skull during an ultrasound. This indicator is used to measure fetal development, estimate fetal weight, and