I am considering to have another child. However, I think I am too old to have (I am late 30s). What is the age range that I should stop considering getting pregnant?

My friend gave birth to a very healthy 2nd child at 40 years of age. Fann Wong gave birth at 42. There are disadvantages of having children too late i.e. it's more tiring to look after them and there are increased risks of birth defects. On the bright side, there are studies which show that moms over 30 have a LOWER risk of having children with major congenital malformations which are not caused by chromosome abnormalities. http://www.webmd.com/baby/news/20140203/babies-born-to-moms-over-35-may-have-lower-risk-for-certain-birth-defects