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The US Zika Pregnancy Registry: A Preliminary Analysis Provides Important Insight

By Amesh A. Adalja, MD, FACP, FACEP, FIDSA, December 16, 2016

The World Health Organization’s (WHO) declaration of a Public Health Emergency of International Concern (PHEIC) regarding Zika—which is no longer in force—was narrowly issued to help determine what role the virus plays in the development of congenital abnormalities such as microcephaly. The causal link between the virus and microcephaly has been definitively established; however, the frequency with which this occurs, cofactors, and any other questions are actively being researched. Modeling studies have given a rate of occurrence of microcephaly of approximately 1% in 1st trimester infections. A new paper, published in JAMA, provides a detailed look at the US Zika Pregnancy Registry (USZPR) to date and offers much insight into the impact of Zika.


USZPR: Collaboration Between State and Local Health Departments and CDC

In this study, Honein and colleagues looked at women with exposure to Zika who had completed their pregnancies between December 2015 and September 22, 2015, via reports made through the USZPR, a collaborative surveillance system established by the Centers for Disease Control and Prevention (CDC). A completed pregnancy included those that resulted in abortion, spontaneous abortion, stillbirth, or live birth.


6% with Defects: All 1st Trimester Infections

This study included 442 pregnant women, with a median age of 28 years. Most of the women (61%) were asymptomatic, and all cases included were travel-related or related to sexual contact with a traveler.

Birth defects were noted in 6% of the pregnancies. Defects were noted in the 21 infants that were born live and in 5 fetuses from pregnancy losses. Brain abnormalities and/or microcephaly were present in 85%. In those without brain abnormalities or microcephaly, encephalocele, hearing abnormalities, and eye abnormalities were present. Importantly, maternal symptoms were equally present in those with and without defects, and no birth defects were found in those women exposed in the 2nd or 3rd trimesters of pregnancy.


Improved Patient Counseling with Data

This study is very important because it gives clinicians a greater sense of the full scope of Zika-related fetal manifestations and their frequency. The robustness of the data contained in the USZPR allows clinicians to have some data at hand with which to counsel patients. The most important counseling topics that can be significantly improved by incorporating the data contained in this paper are the danger of asymptomatic infection to a pregnancy and the lack of Zika impact on pregnancies that have progressed to the 2nd trimester. As the data in the USZPR grows, it will be essential to update these findings and determine whether these early trends—especially 2nd and 3rd trimester infection outcomes—are sustained.



1.Honein MA, Dawson AL, Peterson EE, et al. Birth defects among fetuses and infants of US women with evidence of possible Zika virus infection during pregnancy. JAMA 2016. Accessed December 14, 2016.