My sis and her husband started trying for kids when she was 33. They thought they had plenty of time. After a year they were a little disappointed, but kept trying. They just thought if they had sex more often then it would happen. When she was 35, they went to a fertility specialist and did some preliminary testing. Nothing came back abnormal, so they tried for another year. Finally at 36, they really got to the root of her problem (her Fallopian Tubes). The specialist told her that the egg would never get down her tubes. He told her the only way to get pregnant would be through IVF. They waited a few more months and finally did it.
She is 37 and gave birth last week to TWINS! She got pregnant on her first round of IVF. She only wishes she wouldn't have waited so long to figure out she had a problem. She will be 38 soon and feels she is too old to have more children. They are very happy with the two they have, but she wishes they wouldn't have waited so long.
So, long story short...don't wait!!!!