I really don't think making a joke out of it is the right approach. It can be so tough to get things back to normal when babies and children come along, because you tend to be absolutely knackered a lot of the time. We've had dry spells, but the main thing I want from my partner during those times is affection without the expectation that it will lead to sex. LOTS of affection and telling me how wonderful I am (works both ways of course and I do the same for him) I'm a tactile and affectionate person, but obviously after having a baby your body changes and the way you feel about yourself changes too. I need my partner now more than ever to show me that he loves me, values me, appreciates me and finds me physically attractive. Lots of the time the affection does lead further, but we have both made a conscious effort to be more loving and touchy-feely in general. Also, some sexual stuff has changed for me. I don't really like my boobs being touched anymore (I'm sure this will change again when my breastfeeding days are a distant memory, but for now they are a no-go). Communication is key. Talk to your partner about what turns her on now. Things might have changed in that respect. They have for me and it's so important that my partner understands that. We have amazing sex, it's just very different to how it was, and it took me several months to relax and fully enjoy it (even though I really wanted to) just because I was so anxious about the changes that had happened to my body. I think a better approach would be to sensitively ask if there's anything bothering her about your sex life or anything you need to understand about how things might be different now you have a child.
You do sound like you completely respect your partner and are being incredibly patient, which is great, but most people in relationships want a sexual relationship, otherwise we would just all have lodgers, wouldn't we? So I get why you want to rebuild that element of your relationship. Do you do nice things for your partner? Bunch of flowers or other little gestures that are meaningful to her? Do you do your fair share around the house? There are very few things more unattractive than a man who can't be arsed to stack the dishwasher or put a load of laundry in. You might not see any link between that and your sex life, but if she's running round cleaning up after you and your child constantly without any time to relax, there's every chance she's feeling resentful and highly unlikely to be feeling up for it. Ask yourself if you could be doing more to make her life easier so she has the energy for hanky-panky. I'm only saying this because I have friends whose partners are like big kids who won't lift a finger and they wonder why their sex life isn't what it used to be. I'm NOT saying you are like this, because obviously I don't know you, just throwing it out there so you have another perspective in case it's something you can work on.