JLC circa 70s
>>76534641
Old mother -> mostly problems for the physical carrying of the baby and birth (like miscarriages, poor nutrient transfer, premature, needing c-sections due to poor pelvic strength, etc.), but also heightened risk of diabetes and heart/blood psi issues, anemia and other deficiencies etc.
Old father -> mostly problems for the child's life. Aging increases mutation frequency in sperm. so more likely to get genetic and mental disorders + congenital defects. mainly autism, which we are certainly encountering more of.
Women's bodies are very picky and sensitive and discard the majority of successful implantations, and not necessarily for good reasons, like even despite good gametes and environment. Just 'cause. So when most sperm is extra shiddy, yeah there's way less chance of a baby and when it does get past screening it's a dunce.