1. Maternal age and risk of stillbirth: a systematic review;L Huang;CMAJ,2008
2. Mathews T, Hamilton B (2002.) Mean age of mother, 1970–2000. National Vital Statistics Reports vol 50 no. 1. Hyattsville, Maryland: National Center for Health Statistics.
3. Martin J, Hamilton B, Sutton P, Ventura S, Menacker F, et al.. (2009) Births: Final data for 2006. National Vital Statistics Reports vol 57 no. 7. Hyattsville, Maryland: National Center for Health Statistics.
4. Martin J, Hamilton B, Ventura S, Osterman M, Kirmeyer S, et al.. (2011) Births: Final Data for 2009. National Vital Statistics Reports vol 60 no. 1. Hyattsville, Maryland: National Center for Health Statistics.
5. European Commission: eurostat. Fertility statistics (http://epp.eurostat.ec.europa.eu/statistics_explained/index.php/Fertility_statistics, accessed on 20/01/2013).