Older pregnant women are at higher risks of:
b) chromosomal abnormalities e.g. Down syndrome
c) stillbirth at term
d) having pre-existing medical conditions (e.g. high blood pressure and diabetes mellitus) that may increase risks during the pregnancy
Graph (from Wikipedia) showing increased risk of spontaneous miscarriages with increased age of the mother.
Graph from Newberger D, Am Family Physician 2000 showing that the risk of Down syndrome fetuses in live births increases with mother's age.
Graph from Uma M, American Journal of Obstetrics and Gynaecology 2006 that shows the risk of stillbirth increases from 39 weeks and increases with mother's age.
Proper discussions of the strategies to detect chromosomal abnormalities (if parents desire) and stillbirth at term should be done. Delivery at 39 weeks is a strategy to reduce the risk of stillbirth for older mothers.
Graph from Selma Idring et al, International Journal of Epidemiology 2014 showing increased risk of autism spectrum disorders among the children of older mothers and fathers. Autism of children cannot be detected during pregnancy.