2ND-TRIMESTER SONOGRAPHIC PREDICTION OF FETAL GENDER

Objective: Fetal gender may affect the sonographic determination of ge netic risks for some conditions. The use of gender-specific informatio n depends on the ability to accurately predict gender. This study was undertaken to evaluate factors affecting second trimester sonographic prediction of fetal gender. Methods: Prospective sonographic determina tion of fetal gender was attempted transabdominally in all patients pr esenting for second trimester aminocentesis over an 8-month period dur ing routine preamniocentesis fetal ultrasound evaluation. True gender for each fetus was determined by karyotype. The effects of gender, ges tational age, and presentation on gender prediction were evaluated wit h descriptive statistics, contingency tables, and ANOVA. Results: Two hundred and sixty-one patients between 13 and 22.6 weeks gestational a ge had karyotype confirmation of fetal gender. The mean gestational ag e was 16.5 +/- 1.4 weeks, Gender was assigned sonographically in 73% ( 191/261) and was correct in 96% (183/191). Of the fetuses with sonogra phically unknown gender, 59% (41/70) were female and 41% (29/70) were male (P = NS), A clinically small difference in gestational age was se en in fetuses with sonographically unknown gender (16.2 +/- 1.4 weeks) compared with sonographically predicted gender (16.7 +/- 1.4 weeks) ( P = 0.04). However, neither gestational age categorized by week nor pr esentation significantly affected unknown or error rates. Conclusions: (1) Fetal gender is sonographically identifiable at the time of secon d trimester aminocentesis in 73% of cases during routine preamniocente sis ultrasound examination. (2) Fetal gender prediction is 96% accurat e for males and females.