The sex of a baby can be determined in several ways during pregnancy:
- The most common and reliable method is through an anatomy scan ultrasound, which is typically performed around 18-22 weeks of pregnancy, with 20 weeks being optimal for viewing the baby's genitalia to tell the sex. At this scan, the sonographer can often identify the baby's sex if the baby is positioned well and the genitalia are visible.
- Ultrasound can sometimes identify sex earlier using the "nub theory" from about 11 weeks onwards, but accuracy increases with time: roughly 70% accurate at 11 weeks, nearly 99% at 12 weeks, and almost 100% at 13 weeks.
- Blood tests such as noninvasive prenatal testing (NIPT), which analyzes fetal DNA in the mother's blood, can also indicate the baby's sex as early as 9-10 weeks, with some private labs offering early sex prediction tests from 6-7 weeks, though these are less accurate at very early stages and generally more reliable after 20 weeks.
- Invasive genetic tests like chorionic villus sampling (CVS) and amniocentesis can determine sex earlier (CVS from 11-14 weeks, amniocentesis from 15-18 weeks), but these carry miscarriage risks and are usually done for genetic screening rather than sex determination.
In summary, a typical, safe, and common time to find out the sex of a baby is during the mid-pregnancy anatomy ultrasound at around 18-22 weeks, with earlier options available through blood tests or ultrasound but with varying accuracy and sometimes added costs or risks.
