Validity of a selection of pregnancy complications in the Medical Birth Registry of Norway

Abstract

Introduction The validity of information on pregnancy complications in the Medical Birth Registry of Norway (MBRN) is insufficiently studied. The objective was to examine the validity of information on gestational age, birthweight, medically initiated delivery, and gestational hypertension in the MBRN. Material and methods We randomly sampled MBRN records among women who participated in the population-based HUNT Study in Nord-Trøndelag county and who gave birth during 1967-2012. We estimated the sensitivity, specificity, positive predictive value (PPV) and negative predictive value of information in the MBRN, using hospital records as the reference standard. Results Hospital records were available for 786 out of 797 sampled MBRN records. The PPVs of preterm (<37 weeks of gestation) and early preterm birth (<34 weeks of gestation) were approximately 90%, and the PPVs of low (<2500 g) and high (>4500 g) birthweight were 100%. For medically initiated delivery, the PPV was 28% during 1967-85, but 80% during 1986-2012 and higher among preterm (76%) than among term (51%) births. For gestational hypertension, the PPV was 68%, but 88% of women labeled with gestational hypertension in the MBRN had evidence of gestational hypertension or preeclampsia in hospital records. Conclusions The validity of information on gestational age and birthweight in the MBRN was very good. For medically initiated delivery, the validity was poor before 1985 and satisfactory thereafter. For gestational hypertension, lack of information in hospital records made the evaluation difficult, but our results suggest that most women labeled with gestational hypertension in the MBRN did have a hypertensive disorder of pregnancy.