2 Answers

In the world or just in one particular country? 

According to the NVSS report for 2011, which was published June, 2013: 
Women aged 50 and over—In 2011, 585 births occurred to women aged 50 and over, compared with
571 in 2010 (Tables 2 and 6). The number of births to women in this age group has increased each year
since 1997 (144), when data for women aged 50 and over became available again. (From 1964 through
1996, age of mother was imputed if the reported age was under 10 or 50 or over; see Technical Notes.)
In 2011, the birth rate for women aged 50–54 was 0.5 births per 10,000 women, unchanged since 2006
(data not shown in tables). Because of the small number of births to women in this age group, the birth
rate for women aged 50–54 is expressed per 10,000 women. For rates shown elsewhere in this report,
births to women aged 50 and over are included with births to women aged 45–49 when computing birth
rates by age of mother (the denominator for the rate is women aged 45–49).

If was very difficult to find even this little bit of info, which relates solely to the USA