The earliest you can determine the gender of a baby is around 10 weeks into pregnancy using a Non-Invasive Prenatal Test (NIPT), which detects fetal DNA in the mother's blood with over 99% accuracy. Ultrasound can provide clues as early as 11 to 13 weeks using the "nub theory," but is more reliably accurate after 14 weeks, and most commonly around the 18 to 22-week anatomy scan, where accuracy exceeds 95%.
Timeline by Method
- NIPT Blood Test: Earliest and highly accurate; from about 10 weeks with 99% accuracy.
- Ultrasound "Nub Theory": From around 11 weeks but less certain; accuracy improves significantly after 13-14 weeks.
- Standard Ultrasound Anatomy Scan: Around 18-22 weeks, with about 95-98% accuracy.
- Invasive Tests (CVS, Amniocentesis): Can determine sex early (10-15 weeks) but mainly done for genetic conditions and carry some risk.
Other Notes
- Home gender blood test kits claim accuracy from 6-8 weeks but are not FDA-approved and risk contamination.
- Factors affecting ultrasound accuracy include baby’s position, technician skill, and maternal body type.
- Absolute certainty is only at birth, as false identifications can happen even with ultrasound.
Overall, for the earliest reliable gender determination, NIPT at 10 weeks is recommended, while ultrasound-based gender scans are more common after 14 weeks and especially around 20 weeks for high accuracy.
