I have read a lot in the press recently about how having a scan at 36 weeks can reduce the number of stillbirths. Is this true?
There are two possible advantages in a late scan and at least one possible disadvantage
Firstly, it will determine which way up the baby is lying (the Presentation). At this stage 95% of babies are head down (cephalic), leaving 5%, or 1 in 20 in a breech position. With the current practice of examining the abdomen with our hands and a tape measure, it is obvious that many breech babies are not discovered until advanced labour when the bottom is felt, instead of the head. This situation arises in almost a third of all breech presentations, and usually leads to an unplanned emergency Caesarean Section in a woman who is unprepared for major surgery and quite reasonably expecting a normal vaginal birth. If the labour has advanced to the second stage of labour (pushing), it may be safest for a carefully conducted assisted vaginal breech delivery. This is obviously, not without some extra risk to the baby, and frightening for the mother.
A scan after 36 weeks will reduce the undiagnosed breech presentation and unplanned breech deliveries.
Secondly, a late scan should be able to pick up babies that are not growing well in the womb, in spite of the mother being classified as “low risk”. At the moment the baby’s growth is checked by examination and a tape measure, and only referred by the midwife for extra care if there is a significant reduction in growth. However, as you might imagine the measurements will depend on many other factors beside the baby’s size, eg bowel, bladder, fat, placenta, amniotic fluid, fibroids, which way the baby is lying and of course consistent technique. Some are hawks with the tape measure, and some are doves!
Picking up these growth restricted babies is important as these babies may be at risk in labour and if the pregnancy proceeds past the “best before date”. Sadly, they represent the group of women who have the highest prevalence of late stillbirth. Some of these babies may be saved with extra care and attention and appropriate intervention. It is now very unusual to lose a baby when risk factors have been identified and acted on.
The problem is that late scans also pick up babies that are sometimes larger than average. There is very little hard evidence on the best way to deal with these reports. Early induction and lots of often unnecessary caesareans may result with little advantage to mother or baby.
At the moment, therefore, routine scans are not normally available on the NHS. Further research is needed to define the actual benefits and risks and of course, the cost!
The Doctor and Daughter’s Guide to Pregnancy