CDC Reports New System for Monitoring Cases of Zika in US Pregnant Women

— -- The Centers for Disease Control and Prevention (CDC) announced today that there have been a few significant changes in the way it will be monitoring the number of women with Zika virus infections in the United States and U.S. territories.

Beginning now, the CDC will report the number of pregnant women with Zika virus infection from two new surveillance systems: the U.S. Zika Pregnancy Registry and the Puerto Rico Zika Active Pregnancy Surveillance System. Already, the case count of pregnant women with Zika virus has increased significantly under these new monitoring systems - but what does it really mean?

Here's what you need to know:

What are the new numbers?

As of May 12, 2016, two Zika virus infection surveillance systems are monitoring: 157 pregnant women in U.S. states with laboratory evidence of possible Zika virus infection, and 122 pregnant women in U.S. territories with laboratory evidence of possible Zika virus infection.

Why are these so much higher than the numbers we have been seeing?

Until today, the totals noted only 48 cases of pregnant women with Zika in U.S. states, and 65 such cases in U.S. territories. These numbers came from CDC reports that used a case definition established in consultation with the Council for State and Territorial Epidemiologists, which included only individuals who had laboratory test results and symptoms or pregnancy complications consistent with Zika.

However, recently published reports indicate that some pregnant women with laboratory evidence of a recent Zika infection without symptoms have delivered infants with microcephaly and other serious brain defects. Therefore, starting today, the CDC will report numbers of pregnant women with Zika from the U.S. Zika Pregnancy Registry and the Puerto Rico Zika Active Pregnancy Surveillance System, two systems designed to collect information about pregnancies and birth outcomes among women with any laboratory evidence of possible Zika virus infection, with or without symptoms.

When asked about the big jump in these numbers, the CDC stated: “We have been monitoring pregnant women with asymptomatic and symptomatic Zika infection since February. This is not a change in who we have been monitoring; the change is that we are now publicly reporting the number.”

Are all of these women still pregnant?

They are not, though the CDC notes that the majority of these cases are ongoing pregnancies. The CDC could not provide an exact number, however, on how many of these 279 women were still pregnant and how many were no longer pregnant for any reason.

How many adverse outcomes of pregnancy have been reported?

The CDC says it is not yet reporting the exact number of adverse outcomes (such as microcephaly, other birth defects and miscarriages) “out of concern for the privacy of those families.” The agency did mention that it was “aware of less than a dozen adverse outcomes [related to Zika]."

Is the CDC releasing the specific number of cases of microcephaly and other birth defects associated with Zika?

The agency has not at this point in time but it did not rule out the possibility that it would report these numbers in the future.

Dr. Allison Edwards is the chief resident in family medicine at the University of Colorado. She is a resident in the ABC News Medical Unit.