A review of 80,000 women in England, undertaken by Gordon Smith of the University of Cambridge has found that, for older moms, it’s safer to have the baby born at 40 weeks.
When first-time moms at the age of 35 or older were induced at 40 weeks, only 0.08% of their babies died. Amongst women who waited for labor to start naturally, or who were induced at 41 to 42 weeks, this rate increased to 0.26%.
The placenta plays a big role in this. As time passes, the placenta starts to deteriorate and will be insufficient in supporting the growing baby.
Read more about these findings in this New Scientist article: