Fetal outcome in pregnancies defined as post-term according to the last menstrual period estimate, but not according to the ultrasound estimate

Objective To study the risk of adverse fetal outcome in fetuses that were p ost-term according to the last menstrual period estimate but not according to the ultrasound estimate. Design A total of 11 510 women with singleton pregnancies, reliable last me nstrual period and delivery after 37 weeks were divided into four groups: w omen who delivered at term, i.e. within 259-295 days according to both the ultrasound and the last menstrual period estimate; women who delivered post -term according so the last menstrual period estimate but not according to the ultrasound estimate; women who delivered post-term according to the ult rasound estimate but not according to the last menstrual period estimate; a nd women who delivered post-term according to both the ultrasound and the l ast menstrual period estimates. Stepwise logistic regression was used to te st whether the risk of Apgar score of < 7 after 5 min and transfer to the n eonatal intensive care unit increased in any of the post-term groups. Results There runs no significant difference in mortality between the term group and the three study groups. There was no significant increase in the risk for Apgar score of < 7 after 5 min or transfer to the neonatal intensi ve care unit for pregnancies that were defined as posr-term according to th e last menstrual period estimate but not according to the ultrasound estima te. There was, however, nit increased risk for Apgar score of < 7 after 5 m in in the group that was post-term according to the ultrasound estimate but not according to the last menstrual period estimate. There Ir,ns also an i ncreased risk for transfer to the neonatal intensive care unit in the group that was post-term according to both estimates. Conclusion The effect of ultrasound in changing the estimated day of delive ry to a later elate leaning to pregnancies becoming post-term according to the last menstrual period estimate brit not according to the ultrasound est imate does not have any adverse consequences for the fetal outcome. However , there seems to be nit increased risk for adverse consequences for pregnan cies that are post-tents according to the ultrasound estimate.