outbreak estimated that about 1 in 100 births to women infected in the first trimester resulted in microcephaly a later study has suggested the risk may be much higheraccording to the who the cape verde islands have had three cases of microcephaly related to zika infection martinique has had three and panama has had four colombia has had only seven but the zika epidemic there which began last fall and peaked in february is the second biggest after brazils most babies infected in the early days of the colombian epidemic are due starting in june so the numbers may soon increase rapidly photo a human embryo at about eight weeks credit dr g moscososcience source 3 the virus crosses the placenta and can reach the fetus zika virus has been found in amniotic fluid surrounding microcephalic babies and autopsies have found it in the brains of fetuses that died in the womb the virus was discovered in the brain of a microcephalic baby aborted at 32 weeks six months after the mother recovered from the disease a study released march 29 described the fetus of a pregnant woman who appeared to have contracted the virus on a trip to guatemala the fetal brain appeared normal in three ultrasounds but then stopped growing after the woman aborted the pregnancy zika virus was found in her blood and in the fetal brain photo neural progenitor cells exposed to zika virus the virus is shown in green and cell death is shown in red credit sarah c ogdenjohns hopkins medicine 4 it also attacks brain cells studies in cell cultures and in mice have shown that the virus is neurotropic that is it targets nerve cells including the ones that eventually become the babys brain in a study in cell stem cell researchers exposed fetal stem cells to the virus and found that it particularly attacked cortical neural progenitor cells which ultimately form the brains cortex the region responsible for many higher functions a study in immunedeficient mice found that the virus entered brain cells and caused tremors it killed very young mice but did not kill any older ones that echoed the observations in humans the infection causes grievous damage in newborns but not in adults another study released march 29 found that the same receptor that the zika virus uses to enter skin cells when causing rashes a protein called axl lies on the surfaces of three types of fetal brain cells photo eritania maria at six months pregnant in front of her house in recife brazil in february credit ueslei marcelinoreuters 5 a small study found a big difference in birth defects a small study of 42 pregnant brazilian women published march 4 found that 29 percent of those who had been infected with zika virus experienced grave outcomes to their pregnancies while none of the uninfected women did those outcomes included fetal death tiny heads shrunken placentas and fetal nerve damage that suggested blindness the most shocking finding was