Ultrasonographic Study Of Anogenital Distance Of Fetus At Different Pregnancy Weeks And Its Variation

ObjectiveThe anogenital distance(AGD)of normal male and female fetuses at 22-38 weeks of gestation was measured by coronal section of perineal ultrasound,and its reference range was established.The variation rule of anogenital distance at different gestational weeks was studied to guide clinical ultrasound examination and provide accurate fetal develop-ment data for prenatal screening of fetal reproductive system malformations.Method10400 pregnant women who came to our hospital for prenatal screening by ultrasound were selected randomly.After eliminating all kinds of abnormal conditions that might affect fetal development,a total of 9608 normal singleton fetuses were selected as the research objects.All fetuses were followed up after delivery,and special examination of external genitalia of newborns was carried out to observe whether there were abnormalities in external genitalia,including males.4458 cases of sex fetus and 5150 cases of female fetus,gestational age 22-38 weeks,average gestational age 26.53(±5.14)weeks,the age of pregnant women 19-45 years,average age 28.39(±4.97)years.Philips EPIQ7multifunc-tional color Doppler ultrasound diagnostic instrument,C5-1 convex array volume probe,probe frequency 1.0-5.0 M Hz.The pregnant women with suitable gestational age were examined by routine ultrasound first,then the AGD was evaluated on the perineal section.The distance between the central point of the anus to the posterior margin of the scrotum of the male fetus or the convergence point of the labial frenum of the female fetus was measured,and the data were analyzed statistically to establish the normal percentage of the AGD for the male and female fetuses at different gestational weeks.Mean value and standard deviation range.Regression analysis method was used to establish the regression model of anus-genital distance with gestational age,with gestational age as independent variable and anus-genital distance as dependent variable,and the goodness test was carried out on the basis of determining the regression equation.Univariate analysis of variance was used to evaluate the changes of anogenital distance in fetal hypospadias.Result9608 normal fetuses were divided into a group of gestational weeks.Statistical analysis of the measured AGD data showed that during the whole gestational period,the AGD of male and female fetuses increased with the increase of gestational weeks,showing a linear correlation(r~2=0.808).For male fetuses,the Y-anal-genital distance(cm)=-1.24+0.106 X(gestational weeks)was expressed by the following regression equation..For female fetuses,Y anal genital distance(cm)=-0.32+0.051X(gestational week).According to the normal distribution law,the normal reference range table of anal-genital distance between male and female fetuses at 22-38 weeks of gestation was established.The residual of the regression equation was in accordance with the normal distribution and the homogeneity of variance.Univariate analysis of variance of fetal AGD corrected by gestational age showed that the anogenital distance of fetus was different from that of normal fetus at gestational age in the condition of hypospadias deformity.ConclusionIt is feasible to measure the AGD of male and female fetuses on coronal section of perineum by ultrasound,which can be used as an index to evaluate the development of fetal genitalia.With the increase of gestational weeks,the AGD of normal fetuses increased gradually,and there was a linear correlation between them.The AGD of children with hypospadias deformity is less than that of normal fetuses.The reference values of different gestational weeks of fetuses’AGD are given in this paper.It is confirmed by clinical application that the reference values can be used as a basis for the diagnosis of hypospadias deformity and have high clinical application value.