No, having an ultrasound won’t affect your baby. Ultrasound sends sound waves through your womb (uterus), which bounce off your baby’s body. The echoes are turned into an image on a screen, so your sonographer can see your baby’s position and movements. The frequency or length of the sound waves depends on how far along your pregnancy is and the type of scan being carried out. During an ultrasound scan, the equipment generates a small amount of heat which is absorbed by the part of the body that’s being scanned. Antenatal scans produce less than one degree C. This means they’re fine for you and your baby. It’s only if the temperature of the scanned body tissue rises by four degrees C that harm may be caused.