Methods
This retrospective cohort study was conducted using prospectively collected
perinatal data. Data during pregnancy and at the time of delivery
were entered by trained research nurses. The study population comprised
all singleton pregnancies from 1990 to 2009 that were subject to an
anatomy scan between 16 and 23 weeks of gestation, comprising 97% of
the eligible study population. Any missing key data were obtained from
the maternity care provider. The number of stillbirths per 10 000 ongoing
pregnancies is reported for each week of gestation, as is the cumulative
risk for each individual woman throughout the remainder of pregnancy.