A sensitivity analysis was performed in the crude model and in models 1–3 after exclusion of SGA and LGA births.Numbers of events, event rates, risk differences (the difference in event rate between large discrepancy and reference categories), and numbers needed to treat (NNT = 1/risk difference) were calculated for the two large discrepancy categories in relation to the reference category.According to the International Society of Ultrasound in Obstetrics and Gynecology, clinical decisions should preferably be based on the EDD by US, and based on first trimester ultrasound, if performed.The most frequently used formula for pregnancy dating in Sweden today is based on fetal biparietal measurements during the second trimester US scan, and this formula can be used to predict the day of delivery with a standard deviation (SD) of 8 days.The fetus was therefore larger than expected when dated by US, and the EDD was changed to an earlier date.A large discrepancy was defined as below the 10 percentile (large positive discrepancy) in the discrepancy distribution.In model 3, a diagnosis of diabetes mellitus or preeclampsia recorded during the current pregnancy was added as a covariate to those included in model 2.
Multiple logistic regression analyses were used to calculate crude and adjusted odds ratios (ORs) and their 95% confidence intervals (95% CIs) in a crude model and in four adjusted models (models 1–4).
The aim of this large population-based Swedish register study was to assess whether the discrepancy between LMP-based and US-based EDD is associated with a series of adverse pregnancy, delivery, and neonatal outcomes.
This register-based cohort study included all singleton births, live or stillborn, in Sweden, from 1995 to 2010, with valid documentation of the EDD based on both LMP and US, and a discrepancy between estimates of 20 days or less.
Although the US-based method is superior to the LMP-based method in most pregnancies, some maternal and fetal characteristics, such as the sex of the fetus, may influence the precision of the US-based estimate, and this lack of precision may be associated with adverse perinatal outcomes.
The discrepancy between dating methods and its association with pregnancy-related outcomes has been investigated in a few studies, but these have included a small study size or a limited number of perinatal outcomes.
During the study period, US scanning was offered to all pregnant women and was accepted by .