Under-reporting of live births in Ontario: 1991-1997.

To examine unregistered births in Ontario and consider related factors, including adoption of administrative fees for birth registration.Documents from both the parents and the attending physician are required for births to be entered into Ontario's live birth database. Our study used data from the Ontario Registrar General to look at the prevalence and characteristics of unregistered births, and a survey of municipal clerks to identify municipalities charging fees for parental documentation.The percentage of births going unrecorded increased threefold from 1991 to 1997. The odds of an unregistered birth were higher for teenage mothers, low birthweight babies, and mothers residing in a municipality that charged birth registration fees.The introduction of registration fees by some municipalities appears to account for an increase in unregistered births. It is recommended that the Ontario Registrar General work to remove financial and administrative barriers that compromise birth statistics.