Possibly, but I think this is a very tiny number; there are about 3,000 abortions on medical grounds per year (and bear in mind many of these would be non survivable conditions, rather than survivable-but-disabling like Down's Syndrome) whereas about 60,000 babies are born premature (which is about 10% of all births) so roughly 20 times more.
The last time I was on one of these threads, someone pointed out that there has been a shift in that diseases like Polio and Measles used to cause disabilities in children but because these have largely been eradicated by vaccination, those kinds of effects are seen less often and so this is a sort of shift away from physical towards cognitive impairments instead.
Also, it's not just neonatal mortality which has increased, child/youth mortality in general has improved (presumably healthcare, vaccines, improved safety and supervision) so that in 1970, 24 children out of every 1000 born did not survive to adulthood, with 21 of those not surviving to age 5, whereas in 2021 it is only 5 out of every 1000 children born who die before they reach adulthood, and 4 of these are under 1 year old (there is not enough of a difference in the data to report separate figures for 1-5 year olds). So there are more surviving children and statistically they are more likely to be from backgrounds where they will be disadvantaged, more likely to have delays, attention issues, behavioural issues etc. This doesn't sound like much because it's about 1.5%, but if an average secondary school has about 1000 pupils, that is 15 pupils throughout that school, a primary school has about 300 so 5 pupils in any primary school, who would not have been there in the 60s, 70s, 80s. These children are very vulnerable - so vulnerable that in previous generations they might actually not have survived.
And yes age of parents is relevant, I heard something the other day I think it was on a podcast, saying that the current estimate is that there is an increase of approximately 10% in rates of autism and ADHD due to age of parents. So that is quite a significant increase, although it's not like it's doubling (or more) which is what people seem to want to make it out to be. Apparently this is because the parts of the brain which are affected in these disorders are fairly "new" in terms of evolution - the genetic "templates" for them are less clear and so they can more easily be disrupted by gene mutations, which are fairly common - if a mutation is significant enough to disrupt foetal development massively, then it causes rejection of the fertilised egg, or if this happens at a slightly later stage of development then you would have a miscarriage, if a mutation is more minor that the foetus is allowed to develop, then it might not be clear unless genetic testing is done and then mutations such as those causing neurodevelopmental disorders are so subtle that we cannot yet reliably identify them. There is some research into genes which are involved in the development of ADHD and autism, but it is much more complicated, it's not like Cystic Fibrosis for example where you can have a clear marker and a test to see if you're a carrier for it, there are hundreds and maybe thousands of individual genes which can contribute to individual cases. It seems like we are a while off being able to understand the genetics of these things well.