1. Delayed childbearing: more women are having their first child later in life;Matthews;NCHS Data Brief,2009
2. Pregnancy at very advanced maternal age: a UK population-based cohort study;Fitzpatrick;Bjog,2017
3. Annual summary of vital statistics–2003;Martin;Pediatrics,2005
4. Childbearing among older women–the message is cautiously optimistic;Cunningham;N Engl J Med,1995
5. Pregnancy in the older gravida: how old is old?;Hollander;Obstet Gynecol Surv,1990