Excerpt:
I had my first child when I was 36 years old, which made me want to understand the risks of having children at different ages. Before looking into this, my impression was that the main biological problems with old-age parenthood had to do with not having the necessary health and vigor to care for young’uns, and I had heard that older women have trouble getting pregnant. While those are real issues, there are many others worthy of consideration.
My read of the evidence is that the risks of miscarriage and serious health problems for children, including autism and birth defects, increase significantly with parental (both paternal and maternal) age. The data I could find for most risks is not very fine-grained and not very precise, but I think this qualitative description matches the data: Risks start rising at around 30 years old for both mothers and fathers, rises gradually through about 35 for mothers and 40 for fathers, and then sharply after that.
The "sharp increase or risks" seems correct but is a bit misleading.
For paternal risks, there is indeed an big relative increase "14% higher odds of premature birth" (https://www.bmj.com/content/363/bmj.k4372). But in absolute terms, I would not think of the increase as huge: from ~6% ( based on quick googling) to ~6*1.14=6.84%.
IMO ~1% increase in risks is not something to be concerned about.
Not sure if you saw the full post at the link, but some absolute risks, such as for miscarriage, are much higher. And for me personally a 1% risk of having a child with a serious mental disability is really scary. Perhaps not for you.