Let's Incorporate First-Trimester Screening Into Obstetric Practice

Nuchal translucency measurement will not be a procedure that everyone does in his or her own office. I see more of a “centers of excellence” model or process evolving, in which a patient who is 9–10 weeks pregnant has blood drawn in her obstetrician's office and then goes to another specialized center for the NT measurement. There, the specialist retrieves the lab results electronically, plugs the NT measurement and lab results into the algorithm, and then—on the spot—tells the patient what her risk is. If the patient decides she wants CVS, the procedure could even be done that day.

As in many other parts of health care, patients in rural areas can be at a disadvantage. To physicians in remote areas, I would say, rely on the biochemistry as a first step.

“Accept and Respect”

As a geneticist, I tell all patients that we try to provide information only, and that what they choose to do with that information is their decision. Faced with screening information and the fact that it adjusts odds and does not provide definitive answers, many patients will decide they are happy with an odds adjustment. Others will say, “I don't care what the risk is, I want a definitive answer.”

Both decisions have to be equally respected. With prenatal screening undergoing such significant change, it is all the more important that we accept the fact that intelligent and reasonable people will look at the same data and reach opposing conclusions. We have to accept and respect this diversity.

During my 25 years in the field, I have found that what patients actually do when they are faced with information is often diametrically the opposite—in both directions—of what they thought they would do if confronted with a problem. That's why I believe that one of the most important things we can do is to reassure patients that everything—any decision—is fine.

A trisomy 18 fetus with enlarged nuchal translucency is seen on ultrasound. Courtesy Dr. Mark I. Evans

Prenatal Screening

There was a time when pregnancy and its outcome were clouded in mystery, when fetal outcome was known only at birth. Over many years, that mystery has dissipated as an evolution of technological developments occurred, eventually leading to the discipline of prenatal diagnosis.

In the 1800s, fetal assessment using the Pinard stethoscope was introduced. This was followed by the introduction and use of more refined instruments that similarly focused on assessment of fetal movement and the fetal heart rate. In 1958, Dr. E.H. Hon introduced electronic fetal monitoring—a technology that enabled us to attempt to assess fetal well-being by attributing illness or lack of health to significant changes in the heart rate. After Dr. Ian Donald of the United Kingdom introduced obstetric ultrasound in the late 1950s and early 1960s, we began using more sophisticated technology to assess the global appearance of the in utero environment.

As this succession of technological innovations occurred, the desire of parents and families to know about the well-being of the fetus grew. Parents welcomed the development of more sophisticated ultrasound and their new ability to scrutinize the fetus in even greater detail, assessing not only its anatomical development but also its behavioral and functional states.

Other methods of fetal assessment were introduced, including biochemical analysis of the maternal and fetal blood. We soon reached the point at which we could use an algorithm that incorporated the biophysical findings of ultrasound and the biochemical assessment of maternal blood to gain significant insight about fetal status very early in gestation.

The culmination of this technological evolution has been the development of first-trimester fetal screening. Using various algorithms, we are now able to gain a significant amount of information on fetal development and outcomes early on.

Our guest professor for Master Class this month, Dr. Mark I. Evans, will elucidate the application of first-trimester prenatal diagnosis. Dr. Evans is professor of obstetrics and gynecology at the Mount Sinai School of Medicine, New York, and president of the Fetal Medicine Foundation of America. He is a national leader in prenatal diagnosis and genetics.