The data of the Finnish Medical Birth Registry (MBR) were linked with birth and death certificates in order to investigate discrepancies between the new perinatal database and population and cause-of-death registration. Fifteen percent of the stillbirths were missing from MBR, and there was slight over-representation of stillborns of low weight and short duration of pregnancy among the unrecorded data. Five percent of early neonatal deaths were missed and 14 percent misclassified as surviving newborns. Excluding the first two months, the non-recording rate of liveborn, surviving babies was 1.1 percent with over-representation of plural births among the unrecorded cases. Evidence on missing death certificates for stillborn babies was found. Assessment of rate of non-recording and selection patterns associated with non-recording, and adding of missing cases and missing data on deaths improved the usability of MBR data substantially.