Revolutionary paradigm.(The Master Class)

It is well known that as maternal age increases, so does the incidence of aneuploidy.

Thus, it made mathematical sense years ago to establish a rather arbitrary threshold of 35 years as the age at which the risk of pregnancy loss caused by routine amniocentesis roughly equaled the likelihood of delivering an infant with Down syndrome.

Although some women younger than age 35 years have requested amniocentesis, our advice has been to reserve this expensive and somewhat risky procedure for those at highest risk. To perform routine amniocentesis on younger women would not only have added to screening costs, but would also have tilted the risk-benefit balance, since more pregnancies would be lost than aneuploidies detected.

Nonetheless, a troubling conundrum has always existed within our screening guidelines.

Since fewer women over 35 become pregnant, 80% of babies born with Down syndrome today are born to women under 35. Their absolute risk of aneuploidy is lower, but the higher frequency of pregnancies among young mothers adds up to a dilemma for those trying to establish screening guidelines that are both practical and meaningful.

Fortunately, the efforts of people such as Dr. Ronald J. Wapner, professor and chairman of the department of ob.gyn., ...