I recently had amniocentesis which was normal why was it also sent for a micro arry?

Microdeletions: Microarray is a powerful tool to look for many problems with chromosomes. Aside from traditional chromosome counts, microarray can show subtle deletions and duplications in the dna and predict certain types of birth defects. These are new techniques with many established and emerging applications.

More specific: A routine amnio looks for numeric and structural abnormalities of chromosomes. A microarray can detect specific sites on a chromosome that might be abnormal and a routine amnio would not detect (i.e. Microdeletions or duplications) to name a couple.