1. Australian Bureau of Statistics Births, Australia, 2006 http://www.ausstats.abs.gov.au/ausstats/subscriber.nsf/0/0C4C341C51104DC4CA2573800015C2DC/$File/33010_2006.pdf
2. Centre for Diseases Control and Prevention http://www.cdc.gov/nchs/data/databriefs/db21.htm
3. National Statistics U News release: for the first time women in early 30s have higher fertility rates than women in late 20s http://www.statistics.gov.uk/pdfdir/birthstats1205.pdf
4. New Zealand Health Information Service Report on maternity: maternal and newborn information 2004 http://www.nzhis.govt.nz/moh.nsf/pagesns/73