The fetus was therefore smaller than expected when dated by US, and the EDD was postponed.
Positive discrepancy was defined as the EDD by LMP later than the EDD by US, which corresponded to a less advanced GA estimated by LMP than by US.
The reference category was defined as a discrepancy within 2 days of the median. Delivery outcomes were included if adverse outcomes were expected to be more frequent among large infants at birth because a larger fetal size may be apparent at the time of the dating scan: prolonged second stage of labor (6622, O63.1), delivery by forceps or vacuum extractor (6695, O81), delivery by cesarean section (6697, O82), shoulder dystocia (6604, O66.0), postpartum hemorrhage (666, O72), and perineal laceration: third or fourth degree (6642, 6643, O70.2, O70.3) (Supplementary Table 1).
The remaining pregnancies were defined as a small negative or small positive discrepancy (Fig. To check for any association with the discrepancy between dating methods to infant size at birth, we included small for gestational age (SGA) and large for gestational age (LGA).
In model 1, we adjusted for body mass index (BMI, weight (kg)/height (m30 years, smoking or snuff use, living without a partner, and not being employed.
Initially, the estimated date of delivery (EDD) is generally calculated based on the first day of the last menstrual period (LMP) and may later be modified when an ultrasound (US) scan is performed.
During the study period, US scanning was offered to all pregnant women and was accepted by .