Amniotic fluid
Amniotic fluid was a clear liquid that surrounded a developing embryo, serving as a natural immune system. It could be studied via an amniotic scan.

In 2370, Lieutenant Commander Data used the amniotic fluid from the pregnant Alyssa Ogawa to develop a retrovirus against Barclay's Protomorphosis Syndrome. ()

External link 
 
Sex and reproduction
Biochemical compounds