Pixie are you planning to go into the pharma industry? Is it med chem or process development? I was a process development chemist in fine chems/pharma for about 10 years and I did a PhD and one postdoc.
First off I would note that the UK market for chemists has been a bit crap in the last few years owing to the downsizing in the pharma industry - Novartis closed their site in Horsham, GSK got rid of a couple of sites and has had redundancies in the ones it's kept. AZ have been getting rid of people off and on, and they keep relocating people all over the place. Pfizer is basically gone in the UK IIRC.
In light of all that, but I would have said it before anyway: don't go for the PhD if your main concern is employability in industry. Our department had a lot harder time recruiting good graduates than good PhDs, and there were plenty of PhDs working in "industrial postdocs"/short term contracts because they couldn't find anything else.
As above posters have said, you're usually expected to postdoc after a PhD, and that's a year or two or three, temporary contracts, in far flung places. Fun and interesting, but not great if you want to settle down.
If you go into the chemical industry as a graduate it may hold back your career progression a little but it's perfectly possible to get into management with a degree only, particularly if you're interested in moving sideways into regulatory or pilot plant or manufacturing.
Are you currently working in the chemical industry? As in, you have a permanent job? I would hang onto that like a limpet if I were you, because they are not all that easy to come by. If you're with a good employer, you'll get the year's maternity leave and you'll probably be able to go part time afterwards. I knew people who worked 3 days a week - that's still you spending the majority of your days with your DC.
Another factor against PhD (I'm assuming you're a lab based chemist) is that the safety standards won't be as good as they are in industry, IME. I was pregnant while working in the lab and I had no worries that I was going to get exposed to anything dodgy. In academia not so much care is taken.
If you want to PM me I'll tell you the whole details and what companies I worked for and stuff 