Ultrasound

It is customary in the UK for all pregnant women to have at least one scan during their pregnancy, usually at around 16 to 18 weeks, but sometimes earlier. This is usually done to confirm your dates, and in conjunction with blood tests for assessing any risk of Spina Bifida and Down's Syndrome; and is useful for diagnosis of multiple pregnancy. While it also plays a major role in reassuring mothers that all is well with their baby, it should not be forgotten that the scan is also a diagnostic tool and can sometimes reveal problems in the developing baby.

Ultrasound scans reflect high-pitched sound waves back from internal organs as echoes. These can be electronically reproduced on a screen as a recognizable image of your baby, and can also provide you with a picture you can keep. The ultrasound operator can then 'hold' an image on the screen and measure the length of the baby's thigh to confirm his or her maturity; it's also possible to check the major organs, number of fingers and toes, etc. An experienced operator could probably see what sex your baby is, especially on a scan done later in your pregnancy. He or she won't mention this or tell you unless you ask and he or she is sure. Some hospitals have a blanket policy of never revealing the sex of a baby to the parents at all.

The ultrasound scan is also extremely valuable in seeing where the placenta is placed. Antenatal diagnosis of placenta praevia has made an enormous difference in the safe managing of this type of pregnancy and delivery. If at 16 to 18 weeks the placenta is seen to be low-lying, a subsequent scan in the last three months can show whether or not it has 'moved up', as it often does.

Ultrasound scanning has also made the use of amniocentesis much safer. Being able to 'see' into the womb, and exactly where the baby and placenta are situated, is very helpful in a skilled procedure like this.

Although the long-term safety of ultrasound scanning has not been established, it has now been in routine use for 20 years, and its benefits seem to far outweigh any known negative effects.

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