Actually, age is really a big factor not only in fertility but also when you get pregnant na. As you may have read, the older the female/male, mas lalong at risk for congenital defects, and also miscarriage. At my/hubby's age, extra careful si OB in ordering tests and risk profiles kasi nga malaki ang chances for Down's at kung ano ano pa. In fact, nung pina trisonomy tests ako, based on my personal profile (age) mas mataas nga the risk, pero that risk was lowered after they considered the blood test and the ultrasound tests ni baby.
I have a friend who was in her late 30's and the husband was in his late 40's, early 50's. The girl had a child before, so has the guy (both were previously married to other people). Nung sila na ni friend, nahirapan na sila mag-conceive and the only way for them to conceive was to do IVF. And dahil nga may edad na si friend din, she didn't conceive successfully until she was 40. Now they have a beautiful boy + girl (twins).
Definitely, doable ang pagbubuntis nang late, meron nga hanggang 50's nagbubuntis pa rin. Pero the risk of not being able to conceive is high, the risk of losing the baby is high, and the risk of having congenital defects, illnesses at kung ano ano pa is high.