Determining of gestational age and identification of term fetuses by Ultrasonic colon diameter measurement

Determining of gestational age is of great importance in prenatal care. Nowadays، sonography is accepted as the best method of calculation of gestational age. But as pregnancy enters into the third trimester، the accuracy of parameters determining the gestational age by ultrasound decreases. Therefore، there is a need to new ultrasonic parameters. This study was performed with the aim to evaluate the correlation between gestational age and fetal colon diameter; and finally establishing a normal range of colon diameter in Iranian fetuses. This cross-sectional study was performed on 100 pregnant women who had referred to the hospitals of Islamic Azad University of Mashhad for routine ultrasound assessment at third trimester in 2013-14. The patients underwent sonography. The maximum diameter of fetal descending colon was measured in transverse section، then its correlation with gestational age was assessed by Pearson correlation test. Data was analyzed by SPSS software (Version 16). From 100 screened fetuses، 60 fetuses aged 38 weeks or more، and 40 fetuses aged less than 38 weeks. The minimum and maximum of measured colon diameter in preterm fetuses were 10. 9، 13. 4، respectively and in term fetuses were 13. 5، 17. 9 millimeter، respectively. Statistical analysis showed a significant relationship between gestational age and colon diameter (P=0/98). there is a good linear relationship between gestational age and fetal colon diameter; therefore، it can be used as an independent biometry for determining of gestational age. Also، colon diameter seems to be a good marker for identifying term fetuses.