"Eco" obviously is ultrasound.

This one is an educated guess based on limited context and page 5 here:
https://portal.medicinafetalbarcelona.org/protocolos/es/pato...

The other two references mention "líquido amniótico normal". I often see LA for líquido amniótico, so it's not a huge stretch to think that the N is normal (líquido amniótico normal). If they're concerned about the baby's urinary system, it would make sense that they're looking at the amniotic fluid, since this is composed primarily of fetal urine, so the quantity of amniotic fluid is a good indicator of fetal renal and urogenital function.

You'll need to look at the rest of your context and see if this fits. Good luck!