American mothers in the 30-34 age range have the lowest rate of medical complications during labor and delivery (per table 4 here):

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4418963/

35-39 year olds have slightly higher rates of complications, but the rates are still lower than in teenage mothers. This rank ordering persists even after adjusting for demographics, type of birth, and comorbidities (table 5).