Birthweight and Gestational age
Birthweight (measured in grams) was extracted from the MBRN and was treated as a continuous scale producing a mean value of 3,608 (SD 544.8). Gestational age (measured in days) was also treated as a continuous variable and the mean score was 39.5 (SD 1.72). All maternity units in Norway must notify the MBRN of all births and pregnancies terminating after week 12. The MBRN includes information on pre- and post-pregnancy variables including medication, birth complication, and maternal complications.