And you also can't make assumptions that young mothers will be low risk.
Personally, I had my 1st at just-turned 36, in a low risk pregnancy, which unexpectedly resulted in early PE & a near-100 day NICU stay for DS, plus some ongoing health issues for him. We cost the NHS a fortune.
My 43-year old just had her 2nd; a textbook pregnancy & delivery.
I also work in a high-risk obstetric service; there are women of all ages attending.