This. ^ The fundamental and salient piece of information people are omitting, is that if you go full time, you will STILL be doing the vast majority of the grunt work, and domestic chores, and shopping, and washing, and cooking etc. HE won't do it, because men don't. Most men are lazy when it comes to domestic shit, and believe housework and general domestic stuff to be 'womens work.'
I have been part time for 30 years (Full time for the first 10-12,) and I will never go full time. I do 24 hours (WFH.) DH worked 38-40 hours a week til about 5 years ago (when he hit his early 50s,) but only does 32 hours now, so not THAT many more than me. And he does very little 'domestic duties/housework/life admit etc. I do 95% of it. So like fuck would I be upping MY hours. Never. Not a chance.
I am surprised by the reaction on here, and the YABU vote being so high. I can only surmise these women have been pushed out to full time work by their partners. 
The 'what if HE wanted to go part time' brigade are out in force! But as I said, that's different, because he would go part time and still do fuck all in the house. Thankfully, my DH has never nagged or goaded me into going full time. Even after the kids left home (8-9 years ago.) If he ever had done, I would look at him in a different light. No man should be nagging his wife into working more hours because he needs/wants more income. He should get a better job, and/or work more hours himself.
I have known quite a few women whose husband/partner has nagged and bullied her into going full time - sometimes when the kids were still in primary school, and she resented it deeply, and felt she was being taken away from her children. Caused a huge rift in the relationship with the husband/partner, and unsurprisingly, he did fuck-all around the house when she went full time. The relationships did not last. Mine would not have either, if my husband had bullied and nagged me into going full time - especially when the kids were still in primary school!
@Lazym YANBU. Tell him to get a better, more well-paid job if he wants more income!