In 2004, the Idaho birth certificate was revised for the question on prenatal care. Prior to 2004, the question on prenatal care was based on the month prenatal care began; beginning in 2004, Idaho prenatal care data are based on date of first prenatal care visit. There is a break in the Idaho trend line between 2003 and 2004.
Not all states have revised their birth certificate to the 2003 US Standard Certificate. Prenatal care data based on the 2003 revision of the US Certificate are not comparable with data based on the 1989 US Certificate.