As a peer alluded to, that's going to be for some ideal demographic in their twenties (probably early), hitting ovulation perfectly. Age changes things dramatically:
"Women younger than 30 have about a 20 percent chance of getting pregnant naturally each month. By age 40, the chance of pregnancy is about five percent each month." [1]
Things like IVF do not dramatically change the odds either. They're better of course, but it's far from guaranteed - it's still just a rather expensive roll of the dice.
Then on top of all of this, having children later greatly increases the chances of miscarriage, developmental issues (like Down syndrome) and so on.
Life's brutal here - you're in a race against time, yet the later you start the longer it takes, and the harder it becomes.