The Israeli Maternal Perinatal Database: methods and preliminary evaluation.

The Israel Maternal Perinatal Database (IMPD) includes the 1980-92 birth cohorts and was created using deterministic linkage, based on a unique identity number. This number is assigned at birth for Israeli-born infants and upon acquiring permanent or temporary residential status for immigrants and is used widely. The IMPD includes approximately 1.3 million births and about 400,000 mothers with more than one birth, 40,000 mothers with more than three births and 20,000 grand multipara mothers with four births or more. The pretest-based estimates of incorrectly matched births are 2%. The expected percentage of underlinkage is 5-10% for births occurring before 1985. Since 1985, incorrect maternal underlinkages result only when a birth occurs out of Israel to an Israeli resident. One of the advantages of the IMPD is the ability to estimate linkage reliability, validity and censoring effects by comparison with an external data sources, the National Population Register, which groups each mother with all her living children under the age of 18 years. One of the potential analysis pitfalls is the effect of censoring at entry as a result of influx of immigrants from the former Soviet Union and Ethiopia.