I asked him if there was any way of knowing how fertile I am or how many eggs I have left. He said that although we could do blood tests, the best way of knowing is by charting my cycle and if it becomes irregular/shorter that's a warning sign. Does that sound right? Part of me would like to have a blood test as an added bit of information but my obstetrician has been absolutely fantastic and I would trust him with my life.

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Yep that is right. Fertility kind of "drops off" gradually - so if that's happening and you're charting you will start seeing occasional anovulatory cycles, and some that are longer or shorter than usual and more irregular. Charting gives so much information if you know what you're looking for.

Good luck with it I know how you feel with the clock ticking - I'm nearly 35 and not ready for another child anywhere in the near future but I'm not sure I'm completely finished yet...so I feel the pressure too.