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Outcomes of Pregnancies with Laboratory Evidence of Possible Zika Virus Infection, 2015-2018

The following numbers represent completed pregnancies, liveborn infants with birth defects, and pregnancy losses with birth defects that have been associated with possible Zika virus infection. These outcomes include women who completed their pregnancies from December 1, 2015 to March 31, 2018.

Outcomes for US States and the District of Columbia

Completed pregnancies with or without Zika-associated birth defects

2,360

Liveborn infants with Zika-associated birth defects

116

Pregnancy losses with Zika-associated birth defects

9

As of May 15, 2018, a total of 32 additional completed pregnancies with or without Zika-associated birth defects in the US States and the District of Columbia have been included since the last reporting date, April 17, 2018.

Outcomes for US Territories and Freely Associated States

Completed pregnancies with or without Zika-associated birth defects

4,354

Liveborn infants with Zika-associated birth defects

167

Pregnancy losses with Zika-associated birth defects

8

As of May 15, 2018, a total of 55 additional completed pregnancies with or without Zika-associated birth defects in the US territories and freely associated states have been included since the last reporting date, April 17, 2018.

What these numbers show

The number of completed pregnancies with or without birth defects associated with possible Zika virus infection includes live births, miscarriages, stillbirths, and terminations. Researchers use the standard CDC Zika birth defect surveillance case definition for the US Zika Pregnancy and Infant Registry to determine the liveborn infants with birth defects and pregnancy losses with birth defects. All of these numbers may increase or decrease as new cases are added, or information on existing cases is clarified.

The numbers are separated into two categories:

  1. The 50 US States and the District of Columbia, and
  2. The US territories and freely associated states.

The birth defects reported in these numbers are possibly linked to Zika virus infection during pregnancy. These include

  • Microcephaly,
  • Calcium deposits in the brain indicating possible brain damage,
  • Excess fluid in the brain cavities and surrounding the brain,
  • Absent or poorly formed brain structures,
  • Abnormal eye development,
  • Confirmed hearing loss,
  • Or other problems from damage to the
    • Brain that affects nerves, and
    • Muscles and bones, such as clubfoot or inflexible joints.
What these new numbers do not show

These numbers reflect the outcomes of pregnancies with laboratory evidence of possible Zika virus infection reported to the US Zika Pregnancy and Infant Registry. There may be delays in reporting of pregnancy outcomes, and the numbers will be updated monthly.

These pregnancy outcomes include adverse outcomes from women who completed their pregnancies from December 1, 2015 to March 31, 2018. Pregnancies with possible Zika virus infection that are ongoing after March 31, 2018, will not be included in these numbers. However, state, tribal, local, and territorial health departments may continue to securely send this medical information to the US Zika Pregnancy and Infant Registry. There may be delays in the reporting of pregnancy outcomes, and the numbers will be updated monthly.

All birth defects reported have laboratory evidence of possible Zika virus infection. However, we cannot determine if individual defects were caused by Zika virus infection or other factors.

These numbers do not necessarily indicate recent transmission of Zika virus. The numbers are based on positive laboratory tests at the time of testing or report. Some of these laboratory tests can produce a positive result weeks after Zika virus infection has occurred. For more information about these laboratory tests see the laboratory website.

Where do these numbers come from?

These numbers reflect pregnancies reported to the US Zika Pregnancy and Infant Registry. The Registry cover all US jurisdictions including the 50 US States, District of Columbia, and the US territories and freely associated states.

These systems were established in collaboration with state, tribal, local, and territorial health departments for comprehensive monitoring of pregnancies and infant outcomes of pregnancies with any laboratory evidence of possible Zika virus infection.

The US Zika Pregnancy and Infant Registry is protected by an Assurance of Confidentiality. Under the Assurance CDC is not reporting individual state, tribal, local, territorial, or jurisdictional data to protect the privacy of the women and infants affected by Zika virus.

How are these numbers used?

The data collected through the US Zika Pregnancy and Infant Registry will be used to update recommendations for clinical care, to plan for services and support for pregnant women and families affected by Zika virus, and to improve prevention of Zika virus infection during pregnancy regardless of when the infection occurs.

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