How many ultra-sounds are safe during pregnancy?

There is no proved data that ultrasounds are hazardous to fetus. However, in routine practice, three ultrasounds are done one in each trimester of pregnancy. These are considered totally safe by all the gynaecologists. Some ladies might have to undergo through more ultrasounds if some fetus anomaly is suspected. There is no evidence that these ultrasounds were harmful to fetus. So ultrasound during pregnancy is totally safe. The number of ultrasounds required are decided by the gynaecologists.