Literally every couple I know seems to have fallen into this trap after having children - everyone working full time, but somehow everything home and children is her ultimate responsibility.
I think maternity leave is particularly bad for creating this situation - as you are at home, so you end up doing everything and so end up with ownership of more and more tasks. This never changes when you go back to work.
Meanwhile your DH’s life continues as it ever was, contributing when asked but not taking any initiative. Able to spend 12 hours a day out the house, while you struggle to spend more than 5 minutes away from the baby. So the resentment is twofold.
I have had endless, endless rows with my DH about this. He also has accused me of nagging but I have made it clear that asking him to participate in his own home or family life is not ‘nagging’ and if he just bloody did x or y I wouldn’t need to keep reminding him.
What has worked? It’s still not perfect but I have scheduled days he has to cook etc, scheduled days for each to get a lie in, I have a written list of tasks so what needs doing is visible. I’m still ultimately running the show but at least some tasks are taken off me - and I flat out refuse to discuss or participate in his tasks ie no don’t ask what cloths the kids need or what you should cook - that’s not taking the job away from me.
Also - and specific to your being on Mat leave - are you getting any time alone? I found this was very good for my dynamic with DH as I felt I had some life outside of the baby and the house. And it makes them more confident with decision making and caring for the baby alone.
I assume this is the reason for most divorces - it truly blows my mind though that it’s such an endemic problem, every woman I know has told me some version of this story.