THE IMPACT OF FETAL, MATERNAL AND EXTERNAL FACTORS ON PREDICTION OF THE DAY OF DELIVERY BY THE USE OF ULTRASOUND

In a non-selected population comprising 15 241 women, an evaluation wa s performed of tile impact of fetal, maternal and external factors on the ultrasonic measurement of the biparietal diameter (BPD) and the da y of delivery. The 7824 women who constituted the study population had singleton pregnancies and reliable menstrual histories, and they deli vered spontaneously after 37 weeks. Multiple linear regression analysi s was used. There was a difference in the size of the BPD at the ultra sound scan related to the gender, parity, maternal age, gestational ag e according to the last menstrual period and the experience of the ope rators. There was a total difference of +/- 1 day in the day of delive ry as determined by ultrasound and the factors above. The effect on th e day of delivery is explained by the differences in the BPD. An effec t of gender on gestational length was present as well, which partly co mpensated for the difference in the BPD. In conclusion the accuracy of prediction of the day of delivery by ultrasound is influenced by the gender, parity, maternal age and the experience of tile operator but t hese differences are small and of no clinical importance.