Single mom vs married-how will it affect my tax refund?

Last year when I filed taxes it was as a single mom with a 1 child who was head of household and had daycare expensed to claim. I received almost $4000 in taxes back. This year I got married and I was wondering how much that is going to affect how much I get back for taxes? We have to file married filing jointly> THanks so much for any help!