Via JAMA, an editorial: Preliminary Results From the US Zika Pregnancy Registry | Congenital Defects. Excerpt:
Human illness caused by Zika virus infection has been described for several decades, but this pathogen was in a sense better classified as an infectious diseases “trivia question” before reports of larger outbreaks appeared within the last 10 years. Nonspecific symptoms of viral infection, including fever, rash, arthralgia, and conjunctivitis, have been described for Zika infection, and asymptomatic infection is fairly common. However, now that strong and accumulating evidence has implicated Zika infection during pregnancy in severe central nervous system sequelae after infection of the fetus, there has been increased urgency in acquiring a greater understanding of the pathophysiology of Zika disease, and efforts to control the spread of this virus have escalated.
Among the many unanswered questions associated with Zika virus infection during pregnancy is whether the risk of congenital abnormalities is influenced by the gestational timing of maternal infection (early vs late). There is precedence with other congenital infections to anticipate that infection early in pregnancy will lead to greater risk of severe adverse neurodevelopmental outcomes.
Congenital rubella syndrome, characterized by a variety of clinical features, including central nervous system, ocular, auditory, and cardiac effects, is well described as having a substantially increased risk of fetal infection when maternal infection is acquired early in pregnancy, with few clinical manifestations when maternal infection occurs after 20 weeks’ gestation. For cytomegalovirus, primary maternal infection is less likely to transmit the virus to the fetus early in pregnancy.
However, if fetal infection does occur, the risk of severe, often neurologic birth defects is higher when transmission occurs earlier in pregnancy. Whether the timing of infection affects the risk of congenital abnormalities is critically important for families, physicians, and the development of public health approaches to screening.
The report from Honein et al. in this issue of JAMA provides important preliminary data from the US Zika Pregnancy Registry (USZPR), a surveillance system organized by the Centers for Disease Control and Prevention (CDC) to track pregnancy and fetal/infant outcomes after maternal exposure to Zika virus.
The authors report that among 442 completed pregnancies among women with laboratory evidence of possible recent Zika virus infection, birth defects potentially related to Zika virus were identified in 26 fetuses/infants, including 22 (85%) with brain abnormalities with or without microcephaly. Infants born to mothers in whom infection likely occurred in the periconceptional period or first trimester (9 cases) or in multiple trimesters including the first trimester (15 cases) had a higher risk of birth defects than in cases in which the exposure was later in pregnancy (11% vs 0%). None of the clinically examined anomalies were identified in infants born to mothers when evidence of Zika infection was only within the second or third trimesters of pregnancy.
These data are important because they represent the outcomes associated with maternal Zika infection among US women, although the exposures to the virus occurred in countries with active Zika transmission rather than in the United States.