https://www.newstatesman.com/comment/2022/07/why-the-birth-rate-is-falling
But there’s something more specific to the UK happening, too. For the last few years, the number of women who don’t have kids by their 30th birthday has climbed steadily. But the number who don’t have them by 45 — the point at which the ONS says, in a phrase unnervingly reminiscent of Kazuo Ishiguro’s Never Let Me Go, women “complete childbearing” — has remained fairly flat since the early 2000s. The obvious reading of this data is that women are leaving it later to have children; having fewer kids and a lower national fertility rate are the inevitable results.
Why would they be doing this? This is where we get to the easy question I mentioned: because having a child requires both money and stability, and for more than a decade now the entire world seems to have been conspiring to deny the under-40s either. Since 2007 this country and its economy has rolled from crisis to crisis: the crash, the recession, austerity, the next recession brought about by austerity, Brexit, the pandemic, another recession (a really big one this time) exacerbated by the war in Ukraine. Anyone under 35 has never known the good times.
What they have known, though, is an economy in which wages barely rise, a huge pile of debt if they’re a graduate and a housing market in which the only way to attain secure housing is to buy but the only way of buying is to inherit money, move a long way from the best jobs markets or, preferably, both. Throw in the cost of childcare, often compared to a second mortgage — which, given the size of mortgages these days, is no small deal — and the whole venture seems prohibitively, terrifyingly expensive.
Basically this ^^ and nothing will be done as it's too big and hard.
We're a decade older but got hit badly in 2007 and had been struggling before then due to getting on housing ladder by ourselves no inheritance and having kids relatively young DH was 30. We had our last just before and it was mainly dire and dangerous maternity care that put us off more a lack of job security and housing played a role as well.