What are the pregnancy risks associated with being an older mom?

If >34 at delivery. There are risks for women who will be 35 at time of delivery; those odds rise with age: there are increased risks including difficulty conceiving, having a fetus with abnormal chromosomes, miscarrying (even if chromosomes are normal), developing diabetes or preeclampsia, bleeding, needing a cesarean birth, etc. But help is available, and midlife moms successfully have babies every day now.
Genetic and medical. Older (greater than 35) are at increased risk of fetal complications related to the aging of the maternal eggs. The risks increase with maternal age. Generally , pregnancy complications are related to the overall health of the mother. The likelyhood of acquired medical conditions also increase with age.
Several. The risk of having a genetic abnormality increase as the maternal age increases. The risk of age related diseases increase correspondingly, such as diabetes and chronic hypertension, with associated gestational hypertension.
These vary. It is very common to have children later in life. Most pregnancies in women above the age of 30-35 are healthy. Some risks depend on whether or not it is a first child. Others that increase with age include increased risk for cesarean birth, medical complications like high blood pressure and diabetes, and increasing risk of chromosomal/genetic abnormalities.