From the Guidelines
Yes, it is typically possible to determine the gender of a fetus at 16 weeks gestation through ultrasound imaging. At this stage of pregnancy, the external genitalia of the fetus have usually developed enough to be visible on a high-quality ultrasound. The accuracy of gender determination at 16 weeks is generally quite high, around 95-99%, but it's not 100% guaranteed. Factors that can affect accuracy include the position of the fetus, the quality of the ultrasound equipment, and the skill of the technician 1.
Determining Fetal Sex
During the ultrasound, the technician will look for specific anatomical markers:
- For males: the penis and scrotum
- For females: the labia and absence of male genitalia It's worth noting that detection of discordant external genitalia (1 male and 1 female) in multiple gestations would indicate dizygotic, and therefore dichorionic, gestation 1.
Importance of Later Scans
While gender can often be determined at 16 weeks, many healthcare providers prefer to wait until the 18-20 week anatomy scan for a more definitive assessment. This later scan allows for better visualization of the fetal anatomy overall, including the assessment of chorionicity and amnionicity in multiple gestations, which is crucial for identifying potential complications such as vasa previa and velamentous cord insertion 1.
Primary Purpose of Ultrasounds
Patients should be aware that while early gender determination can be exciting, the primary purpose of prenatal ultrasounds is to assess fetal development and health, not just to determine gender. Regular ultrasounds, including the detailed anatomy scan recommended at 18 to 22 weeks’ gestation, are essential for evaluating congenital malformations and ensuring the best possible outcomes for both mother and baby 1.
From the Research
Fetal Sex Determination at 16 Weeks of Gestation
- Fetal sex can be determined at 16 weeks of gestation with a high degree of accuracy, as stated in the study by 2, which found that sonographic sex determination was feasible in 80.3% of cases and all these determinations proved to be correct.
- The study by 3 also supports this, as it found that between weeks 15 and 16, sex diagnosis was possible in 96.7% of pregnancies during the last 2 years of experience, with an accuracy rate for fetal male gender identification of 99.7% and for female gender identification of 100%.
- Another study by 4 mentions that after 13 weeks, sonographic fetal sex determination is accurate in 99% to 100% of cases without malformed external genitalia, which suggests that at 16 weeks, the accuracy would be similarly high.
- The use of ultrasound for fetal sex determination at 16 weeks is also supported by the study by 5, which found that predictions made after 14 weeks gestation were 100% accurate.
- Additionally, the study by 6 found that fetal sex can be diagnosed by ultrasound with a high level of accuracy, although it notes that cell-free fetal DNA (cffDNA) can determine fetal sex noninvasively during the first trimester, which may be an alternative option for some families.