Abstract：Objective To investigate the gender difference of the distance between anus and external genitalia (“anal distance” for short) and its correlation with gestational age. Methods A total of 1488 fetuses with gestational age ≥20 weeks were selected from Daxing Hospital Affiliated to Capital Medical University from January to September 2019. According to gender, they were divided into male fetus group (933 cases) and female fetus group (555 cases). According to gestational age, they were divided into 20-24 weeks group (390 cases) and 24+-28 weeks group (240 cases), 28+-32 week group (296 cases), 32+-36 week group (216 cases) and >36 week group (346 cases). The anal distance of different gender fetuses group in the same gestational age and the anal distance of different gestational age fetuses group in the same gender were compared; and correlation between gestational age and anal distance of different gender fetuses were analyzed. Results The anal distance of male fetuses group in the same gestational age was higher than that of female fetuses group, and the difference was statistically significant (P < 0.05). There was statistically significant difference in the anal distance between different gestational ages group in the same gender fetuses (P < 0.05). Anal distance of male and female fetuses were positively correlated with gestational age (r = 0.872, 0.820, P < 0.01). The regression equation between anal distance and gestational age of male fetuses was Y = 0.103X-1.213. The regression equation between anal distance and gestational age of female fetuses was Y = 0.056X-0.623. Conclusion Gestational age and gender of fetus should be considered in clinical evaluation of anal distance.
2021, Vol. 18 
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