Zika and microcephaly: Microcephaly is a birth defect where a baby’s head is smaller than expected when compared to babies of the same sex and age. Babies with microcephaly often have smaller brains that might not have developed properly.
Zika virus infection during pregnancy is a cause of microcephaly. During pregnancy, a baby’s head grows because the baby’s brain grows. Microcephaly can occur because a baby’s brain has not developed properly during pregnancy or has stopped growing after birth.
Congenital Zika syndrome is a pattern of birth defects found among fetuses and babies infected with Zika virus during pregnancy. Congenital Zika syndrome is described by the following five features:
Not all babies born with congenital Zika infection will have all of these problems. Some infants with congenital Zika virus infection who do not have microcephaly at birth may later experience slowed head growth and develop postnatal microcephaly. Scientists continue to study how Zika virus affects mothers and their children to better understand the full range of potential health problems that Zika virus infection during pregnancy may cause.
Based on the available evidence, we think that Zika virus infection in a woman who is not pregnant would not pose a risk for birth defects in future pregnancies after the virus has cleared from her blood. From what we know about similar infections, once a person has been infected with Zika virus, he or she is likely to be protected from a future Zika infection.