For those pregnancies that do continue, some 15 percent are lost before 20 weeks - and this figure increases with maternal age.

Advancing maternal age and a patient history of previous spontaneous abortions are the two leading risk factors.

Trisomy has been determined to be a function of maternal age.

Association was found, for instance, between increasing maternal age and the frequency of Down's syndrome.

Indeed, it is worth remembering that the effect of birth order may vary with maternal age.

Though maternal age and birth order have an independent effect on the viability of the fetus, that act together.

At 42 she is, in medical parlance, of "advanced maternal age."

By the 1970's, amniocentesis had become available to women of advanced maternal age.

But it is the first study to systematically examine the risk of 43 other common birth defects relative to maternal age.