First-trimester determination of fetal gender by ultrasound: measurement of the ano-genital distance

Abstract

Abstract:Introduction: Early ultrasound fetal sex determination is of obvious interest, particularly in

Fetal anogenital distance using ultrasound

“…AGD measurements were taken on the tangential section of the fetal perineum, where the anal sphincter would first be observed. AGD was measured from the centre of the anus to the base of the scrotum in males and to the posterior convergence of the fourchette in females using electronic callipers, following the same procedure used in previous research measuring fetal AGD (Figures and ). For this measurement to be taken, the fetus' legs must be apart to accurately visualise the scrotum (in males) and fourchette (in females).…”

“…Sex assignment was performed by observation of sonographic landmarks such as labial lines or fetal scrotum, in line with the established gold standard, and was further confirmed at birth. As there was slight variability in AGD measurement due to placement of the fetus, several measurements (range 1‐3 freeze frame measurements) were taken and averaged for interobserver reliability purposes.…”

“…AGD is highly sexually dimorphic in both animal and human studies. The sexual dimorphism can be observed from as early as 11 to 13 weeks of fetal gestation in humans . AGD continues to increase after birth and is correlated with birth weight, and the differences observed in AGD prenatally are maintained across an individual's lifespan .…”

“…In rodents, AGD length has been experimentally shown to be influenced by prenatal androgen exposure during the prenatal “masculinization programming window” (MPW) . AGD is highly sexually dimorphic in both animal and human studies. The sexual dimorphism can be observed from as early as 11 to 13 weeks of fetal gestation in humans .…”

“…Measuring AGD in 2D ultrasound scans has been shown to be feasible and reliable . This suggests that this measure has the potential to aid in the early identifications or understanding of pathogenesis of genitalia development, PCOS, and anorectal and male genitalia malformation. However, there may be population‐specific differences in this measurement, with ethnicity or other regional factors affecting AGD centile charts and reference ranges .…”