Case Study Suggests Zika Virus Can Cause Stillbirths and Congenital Defects

A case study suggests Zika may cause stillbirths and congenital defects in infants of mothers who become infected with the virus. Nacho Doce/Reuters

As the Zika outbreak continues, evidence is mounting in support of the theory that the virus is the reason why than 4,000 infants in Brazil have been born in recent months with microcephaly, a condition in which a baby has an abnormally small skull and underdeveloped brain.

But a new paper, published Thursday in PLOS Neglected Tropical Diseases, suggests exposure to the virus can also result in other pregnancy complications: congenital defects and even stillbirth.

The paper recounts details of one pregnancy in Salvador, Brazil. After labor was induced in the 32nd week of her pregnancy, a 20-year-old woman delivered a stillborn in January. In an autopsy of the infant, physicians identified severe inflammation in the central nervous system and an absence of the cerebral cortex. The doctors detected the Zika virus in other regions of the brain, cerebrospinal fluid and amniotic fluid.

Study author Dr. Albert Ko of the Yale School of Public Health says the Zika virus appears to also cause hydrops fetalis, an abnormal accumulation of fluid in fetal compartments (which eventually develop into organs like abdomen, lungs and heart). Pregnancy complications from the virus, he says, can also result in hydranencephaly, which is a complete absence of brain tissue.

The woman profiled in the case study had a normal, healthy pregnancy up until her 18th week. But then an ultrasound revealed that the fetus' weight was far lower than it should have been at that point in the pregnancy. Throughout the duration of her pregnancy, the patient didn't report experiencing any symptoms of Zika, such as fever, rash or body aches. (Only about a quarter of all people who become infected with the virus actually have symptoms.)

However, since evidence of Zika was detected in tissue and fluid samples from the infant, physicians highly suspect the virus is the cause of the pregnancy complications and stillbirth.

This single case study can't tell us everything about every potential pregnancy outcome that involves exposure to the Zika virus. But it does reinforce how little is still known about Zika's potential impact on fetal development.

Ko and his team are now evaluating newborns who were born at three hospitals in Brazil and have microcephaly. In particular, they are studying the differences between babies who have microcephaly and those who do not. Ko is concerned the virus may be affecting fetal development in ways not as immediately recognizable as microcephaly. Babies that look healthy, he says, may turn out to have some central nervous system abnormalities. In scans of some infants exposed to the virus, Ko and his team have identified a number of abnormalities such as lesions in the brain and eyes.

Ko says a review of epidemiological data on the Zika virus in Brazil and cases of microcephaly suggest that women infected with the virus in the first trimester are at highest risk for an abnormal pregnancy.