Fetal heartbeat at 122 bpm 14 weeks 3 days

We're said to be having a girl from the chromosomal test taken at 11 weeks. Her heartbeat that day was 168 bpm. We went in for another checkup at 14 weeks 3 days and her heartbeat is now 122 bpm. I feel like that may be a little slow? My doctor didn't seem to be worried about it at all, just curious what other moms think.