Objective: To determine whether the frequency of soft sonographic aneuploidy markers varies by fetal sex.
Methods: We identified all singleton fetuses with known sex undergoing genetic sonography at 17 weeks' to 21 weeks 6 days' gestation in a single perinatal center from January 1, 2000, to December 31, 2003. Markers studied were biparietal diameter/femur length, transcerebellar diameter, ear length, echogenic bowel, femur length, humerus length, absent middle fifth phalanx, nuchal fold, renal pelvis dilatation, echogenic cardiac focus, and choroid plexus cysts. Additional information extracted from the prospectively ascertained database included maternal age, referral indications, and chromosomal analyses. Multiple gestations and fetuses with structural or chromosomal abnormalities were excluded. The study received exempt review status by the Institutional Review Board. Dichotomous variables were compared by the chi(2) or Fisher exact test; continuous variables were compared by the unpaired t test.
Results: In total, 4057 eligible fetuses, 2103 male and 1954 female, were examined at 18.9 +/- 0.9 weeks (mean +/- SD). Referral indications included maternal age of 35 years or older (n = 2983), abnormal second-trimester serum screen results (n = 610), soft marker on sonography (n = 583), prior aneuploid offspring (n = 24), and other (n = 125). More than 1 referral indication was possible for a given fetus. Overall, male fetuses exhibited echogenic fetal bowel (odds ratio, 1.76; 95% confidence interval [CI], 1.14-2.72; P = .009) and renal pelvis dilatation (odds ratio, 2.00; 95% CI, 1.30-3.09; P = .001) significantly more often than female fetuses. However, when fetuses were evaluated for single isolated markers, only male predominance of renal pelvis dilatation persisted (odds ratio, 2.32; 95% CI, 1.32-4.09; P = .003). No markers had increased frequency in female offspring.
Conclusions: Male fetuses exhibit a significantly increased frequency of renal pelvis dilatation compared with female fetuses. Sex-specific adjustment of sonographically derived aneuploidy risk does not appear to be indicated. However, a larger series of fetuses with trisomy 21 and pyelectasis is required to assess sex-specific risk adjustment for this marker.