Having gone through IVF with my wife for our two kids I find some of the comments in this thread very disturbing. That people compare having kids with a "lifestyle choice" is extremely weird to me. We're not talking about cars, or even pets, here, people, but by far the main reason 2 people chose to live together, and the way life works. Adoption is not an option for everyone, or in every country, by the way. It is extremely tough to adopt a kid in some parts of the world. Also, not everyone's made for it. Again, this is not a car, but a very important choice that could end up breaking a couple very badly. It's perfectly understandable to me that people would try everything they can to make it happen.
Furthermore, the cost of IVF is an order of magnitude higher than the costs of diapers, child care and raising kids in general. It's not covered by health insurance for the most part, takes months, sometimes years, with unguaranteed results. Telling people "wow, you can't afford an IVF but you think you'll be able to afford child care" seems just completely ignorant to me. We spent more on IVF in 18 months than we've spent on our kids in total for the past 5 years. As a matter of fact, the only time in my life that my wealth hasn't increased was when we had to pay for IVF. That time of my life is visible to me every time I look at my retirement target and graphs.
As others have mentioned, time doesn't play in your favor with these things either. It's not a thing you can save for, as the longer you wait, the smaller your chances get.