Many families first notice 3q29 microdeletion syndrome when a baby has feeding difficulties, poor weight gain, or low muscle tone that makes the body feel floppy. As toddlers, the first signs of 3q29 microdeletion syndrome often include speech and developmental delays, challenges with coordination, and sometimes distinctive facial features that prompt a genetics referral. In some children, learning differences, social or behavioral concerns, or an unexpected result on chromosomal microarray testing during an evaluation for delays is how 3q29 microdeletion syndrome is first noticed.