MODEL RELEASED. Ultrasound scan. Pregnant woman holding an ultrasound scan of her foetus in front of her swollen abdomen. A transducer placed over her abdomen produced high frequency sound waves, which were reflected back to the transducer by the foetus' tissues. On the scan, the foetus' head is at centre, and its body at centre right. Ultrasound allows the foetus' health to be assessed early on and enables the date of birth to be determined more accurately. This woman is eight months (32 weeks) pregnant.