please help.

Maisa
Hi girls 
So my doctor called me today to set up other ultrasound , I did one last Tuesday at 18th weeks and I was very happy because we found out we are having a girl, and we already have a boy... well the doctor told me they found a little bit  of calcium deposited in the baby's intestines, I don't know what does that mean, she said they need to check again to make sure things were okay. 
Anyone has ever experience that with any pregnancy. 
Thank you