Ultrasound dating at 12-14 weeks of gestation. A prospective cross-validation of established dating formulae in in-vitro fertilized pregnancies.
Objectives To determine the accuracy of established ultrasound dating formulae when used at 12-14 weeks of gestation. Methods One-hundred and sixty-seven singleton pregnancies conceived after in-vitro fertilization (IVF) underwent a dating scan at 12-14 weeks of gestation. Gestational age at the dating scan was calculated by adding 14 days to the number of days between the date of oocyte retrieva