During pregnancy, there are lots of confusions regarding ultrasound in many health/medical centres. All medical centres perform ultrasound in the first trimester of pregnancy for determining the delivery date of the woman. But some health centres perform one ultrasound every 3 to 4 weeks during the third trimester. Even, some medical centres are performing ultrasounds every 2 weeks. Ultrasound is not harmful in any condition for the baby and mother.