[Information on parity in the medical registry of births of the National Board of Health. Validation with the help of a new fertility database in Danish Statistics].

Information on parity from the Medical Register of Births kept by The Danish National Board of Health was compared with a parity value calculated with the aid of a new, individual-based Fertility Database compiled by the Danmarks Statistik. The parity information contained in the Medical Register of Births is recorded by the midwife at each birth, where the woman's number of previous live-births is noted. The Register on Population Statistics records live-born infants with reference to their mother, and parity is calculated in the Fertility Database on the basis of these records. The results show a very high degree of accordance between the two measures of parity. More than 99.5% of women with parity one who have given birth since 1978 are classified as such by both systems. Due to an ambiguity in the midwife's birth notification form there has previously been uncertainty regarding the classification of first-time mothers based on the information contained in the Medical Register of Births. This evaluation shows that this information can be regarded as valid.