When a fetus has no amniotic fluid, ultrasound visibility is severely impaired.
Amniotic fluid appears black in an ultrasound scan. The fetus shown in the image no longer has any black areas around its body. It gives the appearance of being “vacuum-packed” within the amniotic cavity. In such cases a fine needle can be used to infuse a replacement fluid into the amniotic cavity. Where we suspect that a leaking amniotic sac may be responsible for the absence of amniotic fluid, we also infuse a blue dye. If the amniotic sac is indeed ruptured, the dye will appear in the vagina.