Ultrasonagraphy provides a picture of a fetus by means of bouncing high-frequency sound waves off the baby. It is useful for dating the pregnancy, checking for major abnormalities, to see if there is more than one baby, locating the placenta and assessing the cause in cases of bleeding in pregnancy. It is routine in many hospitals at around 16 weeks of pregnancy, and you may be under pressure to accept a scan even if you are having your baby at home.
The actual procedure involves lying on your back on a narrow trolley while a blunt probe is scanned across your abdomen, which is lubricated with conductive gel. A sometimes blurred picture is built up on a nearby screen. It is possible to freeze the picture so that specific measurements of the baby can be made to assess the gestational age.
You might prefer not to have a routine scan if you are sure of your dates and would prefer not to know if the baby had an abnormality, or would not choose termination if it had. If you are having more than one baby the fact is almost certain to be detected by abdominal palpation at a later stage, but you might opt for a scan if you felt there was reason to suspect a multiple birth. This might be because you put on an unusual amount of weight, your girth was bigger than that of other women at the same stage of pregnancy, you felt a lot of movement, or were excessively nauseous or experienced a lot of vomiting. Some mothers expecting more than one baby find they get extra tired. It is important to know if you are having twins if you want a home birth.
The benefits of ultrasound can be considerable, however it may be too early to be certain that it is completely harmless. After all, X-raying unborn children was initially thought to be harmless, and subsequently turned out to cause malignancies in childhood. Questions are starting to be raised about its safety; if you have any doubts about it, look at the article by Marsden Wagner on ultrasound published in Midwifery Today (www.midwiferytoday.com).
AIMS can supply you with a sheet for your baby’s ultrasound record to be filled in by the operator. See www.aims.org.uk for information about how to obtain one.
Although undoubtedly very valuable in situations where there is some reason to be concerned about the pregnancy, there are instances where the routine use of ultrasound gives rise to anxiety and its accuracy is in question. Its value as a diagnostic tool is dependent on the skill of the operator: it is possible for major abnormalities such as exomphalos (where the gut develops outside the abdomen) to go undetected by relatively unskilled operators; its accuracy for dating and detecting babies that are not growing well are also questionable; and it may also pick up abnormalities that appear to be present in pregnancy but which are not there at birth. These situations are responsible for considerable distress and may have a lasting effect on a mother’s relationship with her child; clearly this cannot arise if you do not have ultrasound.