There may not be a cliff, but if you look at http://www.advancedfertility.com/ivf-age.htm http://www.advancedfertility.com/ivf-age.htm you can see that the IVF

There may not be a cliff, but if you look at http://www.advancedfertility.com/ivf-age.htm http://www.advancedfertility.com/ivf-age.htm you can see that the IVF success rate is halved going from 30 years old to 40, and then halves twice more by age 44. If you are going to need help with fertility -- and lots of women do -- you are vastly better off discovering it at 30 than at 40. (Re: the article, the interesting question then becomes how much of that decline is due to reduced egg quality. If that's a major issue, then freezing eggs at 30 might be a huge win.)