Outstanding Questions: Zika’s Impact on Maternal and Child Health

The emerging Zika virus poses some unique challenges to patients, doctors, and public health practitioners that aren’t generally a focal point of emergency response efforts. The link to congenital birth defects – including, but not limited to, microcephaly – and Guillain-Barre Syndrome has generated a great deal of concern. As of March 7th, 2016 the CDC has identified 37 countries, mostly in Latin America and the Caribbean, which have active Zika virus transmission. The numbers of reported cases continues to climb as the arbovirus spreads to new locations.

Concerned about the implications for expectant mothers and their unborn children, the World Health Organization (WHO) declared the Zika virus and its yet-to-be-proven association with severe birth defects a Public Health Emergency of International Concern (PHEIC) on February 1st. As a result, basic research, public education, and public health surveillance of the virus has increased dramatically.  Government agencies and organizations all over the world have released guidelines for expectant mothers, travelers, laboratory workers, and clinicians. In the US, the CDC has advised that expectant mothers not travel to effected countries, and that men who may have been exposed to the virus use appropriate protection to avoid sexual transmission. For women living in effected nations, there is an unavoidable risk for infection which cannot be minimized by travel recommendations. To lower the risk for Zika-related fetal development complications, local governments have gone so far as to advise delaying pregnancy. Here are some examples:

  • Brazil’s Ministry of Health (MOH) advised women in the northeastern region of the country, where the Zika virus is most prevalent, to delay pregnancy.
  • Columbia, with the second highest incidence of Zika virus infection, has advised waiting eight months to get pregnant.
  • El Salvador’s MOH suggested the biggest delay on conception, advising deferred pregnancy for two years, until 2018.
  • Jamaica’s MOH has recommended that women delay their pregnancies for the upcoming six to twelve months.
  • Ecuador has recommended delayed pregnancy, but has not specified a timeline.

The unprecedented nature of these recommendations, and their temporal variability (ranging from 6-24 months), indicates that there’s still a significant amount we do not yet understand about the impact of Zika virus infection on mothers and their unborn children.

On February 29th, the Institute of Medicine released their Workshop brief outlining some of the potential research priorities for Zika going forward, including priorities related to understanding more about Zika and pregnancy. As part of the workshop, Dr. Sonja Rasmussen, an expert on pregnancy and birth defects related to infectious diseases, and a member of the Zika response team at CDC, provided a list of outstanding questions related to Zika and pregnancy, including:

  • How often does transmission of Zika virus from mother to fetus occur (what percentage of cases of infected pregnant mothers)?
  • How often does fetal infection result in congenital defects?
  • What other defects are related to congenital Zika infection?
  • What is the best way to diagnose Zika related problems in utero?

Researchers are beginning to work on finding answers to those important questions, but in the meantime, we also need to determine what protective actions women can take now.

The answer to this question will likely differ depending on the population and geographic location. In South and Central America and the Caribbean, where Zika is expected to spread rapidly, experts hope that herd immunity, which can be protective for more vulnerable populations, will develop quickly. In these areas with widespread disease, it is also the hope that women who are infected before pregnancy will develop immunity that will be protective in later pregnancies.

Given these epidemiologic assumptions for areas with widespread disease, public health recommendations for women to delay pregnancy for some period of time may make sense biologically. However, it is important that we continue to gather data about the incidence and prevalence of disease in countries where Zika is widespread to have an idea of how long women should delay pregnancy. In addition, it will be essential to understand more about immunity, whether initial infection really does confer immunity against future infection and if so, how long that immunity lasts.

That being said, recommendations to delay pregnancy for extended periods of time must be considered in the context of other important factors. Many Latin American nations do not have sufficient sexual education or affordable birth control options to adequately support the new demand that Zika has caused. This problem is compounded by the ongoing occurrence of sexual assault and deep cultural ties to Catholicism, which traditionally prohibits the use of birth control. Without readily available and affordable contraceptives, more women are expected to turn to unsafe and illegal abortions. New campaigns for extended access to medically attended abortions in Latin American nations have quickly arisen as more cases of microcephaly appear. Additional investment in public health education, family planning resources, and pre-natal care will be absolutely necessary.

In the US, Zika will likely not be as widespread as it is in the Caribbean, Central and South America. Sporadic local outbreaks are likely to occur, particularly in the southern US, where temperature is favorable and Aedes aegypti mosquitoes are plentiful, but outbreaks will probably not reach the point where herd immunity is achieved. In addition, most women in the US will not be exposed before they are pregnant and thus won’t have the same immunologic protection as women in endemic areas.

So, in the US, carefully crafted and targeted recommendations about pregnancy will be necessary. In the event that limited transmission of Zika does occurs in the US, it is conceivable that women of child bearing age in effected regions may be advised to avoid pregnancy until transmission is interrupted. Alternatively, CDC could opt to leave the decision up to the mother, her partner, and their healthcare provider while continuing to provide guidance and information. In addition, continued refinement of guidance regarding sexual transmission is crucial. Giving couples some idea of how long after infection that sexual transmission can occur will be necessary in order to improve compliance with recommended protective measures.

For the time being, public health messaging and reinvigorated mosquito control efforts are the best tools to prevent Zika infection. Public health officials will need to be careful and thoughtful about these recommendations, and mindful of second order impacts when telling women to delay pregnancy. But, with the information we have now, it seems that these recommendations are not unwarranted or overly cautious.