Fetal outcome when the ultrasound estimate of the day of delivery is more than 14 days later than the last menstrual period estimate

Abstract

Objective. To evaluate the effect on fetal outcome of changing the estimated day of delivery as calculated according to ultrasound measurements more than 14 days later than the day estimated according to the last menstrual period. Design. A non-selected population comprising 15,241 women was evaluated. A study group (the day of delivery based on the ultrasound estimate being changed to more than 14 days later than the estimate based on the last menstrual period) and a control group (the two estimates being within 7 days of each other) were compared regarding various parameters concerning fetal outcome. Results. Changing the estimated day of delivery, based on the ultrasound evaluation, to a date 14 days later than the day of delivery as estimated according to the last menstrual period did not influence the risk of abortion, perinatal death or transferral to the neonatal intensive care unit. There was a difference of 3 days in the accuracy of the prediction of day of delivery between the two groups. There was a greater number of infants with a birth weight below 2500 g in the study group, but no difference was found between the groups in the number of infants with a birth weight < 2 SD from the mean according to the ultrasound estimate. Conclusion. There was no indication of any adverse consequence of the routine scan and change of estimated day of delivery among 15,000 pregnancies in a non-selected population.