Yes, a 20-week pregnancy scan, also known as an anatomy scan, can often determine the gender of the baby. However, it is not always guaranteed and depends on various factors such as the position of the baby and the expertise of the sonographer. The accuracy rate for determining gender during this scan is generally around 80-90%. It is important to note that some healthcare providers may have policies against revealing the gender if it is requested by parents. Additionally, there are other non-invasive prenatal tests available that can provide more accurate results for determining fetal sex, such as cell-free DNA testing or amniocentesis.