The more we learn about Zika, the more complex (and worrying) the virus seems — especially for expectant moms and babies. In addition to being linked to the birth defect microcephaly, the virus may also be linked to a severe joint condition that shows up at birth, new research suggests.The research , published today in the BMJ, comes from a team based in the Brazilian city of Recife, which is at the heart of the outbreak there. As of March, 104 children were under observation for what the researchers thought was Zika.Of those children, the researchers focused on seven who were also born with arthrogryposis , a severe condition in which the muscles around the joints don't develop properly, resulting in weak or stiff joints. After scanning five of the kids' brains, they found a particular pattern of calcification that suggested the condition was due to neurological issues rather than problems within the joints. Additionally, six of those children also had microcephaly Because this is a small observational study, it definitely doesn't prove a causal link, but this isn't the first time Zika has been (tenuously) associated with arthrogryposis. In fact, two studies published this January (one published in Ultrasound in Obstetrics & Gynecology and the other released by the CDC ) provided early evidence that the two issues may be linked. This new study is the most detailed look at the possibly Zika-related deformities. Other research has also linked the virus to Guillain-Barré syndrome , an autoimmune disorder that can lead to severe paralysis.