Since they said it with a smile on their faces, it means they were probably just joking, and it's fine to express your understanding and reliance on your in-laws. You can say that they have worked hard all their lives and it's time for them to take a break, so you don't have to worry about bringing up the kids.
More filial piety to the in-laws is deserved, although they did not raise you, but she raised your husband, so since you love your husband, you have to understand the son's feelings towards his mother, you have to honor his mother with him.
You also have parents, if your husband and your parents talk back and ignore, you will be happy? So give your mother-in-law more smiles and talk to her more. If you are good to his mom, he will naturally be good to yours.
The more you expect from your mother-in-law, the greater the disappointment. It's not realistic to expect your mother-in-law to call you to ask for help or to prepare something for your child, because she hasn't been with your daughter-in-law for very long and doesn't have a lot of affection for her, and the kids haven't even met yet, so there's no way to talk about affection.
Expecting your mother-in-law to take care of you or your child is even more of a hassle, as your mother-in-law is never a mom, and you can't work or offer your daughter-in-law anything during the month of her pregnancy, but instead you have to serve her, and your mother-in-law will not be too happy about it.
After all, in-laws are elders, and it's best for daughters-in-law not to argue with them. Daughters-in-law can let their in-laws know their own positions through practical actions, so that she knows that she's not right, so that she will respect you and look at your relationship in a friendly way.