What does ‘engagement’ of my baby’s head mean?
Your baby’s head is engaged when the widest diameter of your baby’s head is below the brim of your pelvis.
A pregnant woman will often know her baby “has dropped” (is engaged) because of a very intense feeling of fullness in her pelvis. She will also be aware that the height of her uterus is less and there is now a gap between the bottom of her rib cage and her uterus. As a consequence, she will be aware she has less indigestion and heartburn and that it is easier to eat and even to breath.
Sometimes a baby’s head can be engaged one day and not the next. It all has to do with the relationship between the size and position of your baby’s head, the size and shape of your pelvis, and how firm your uterus is in pushing your baby’s head into your pelvis.
In your second and subsequent pregnancies, the uterus is often “looser” and so there is often no reason for your baby’s head to be engaged before you are in labour.
When does engagement happen?
In your first ongoing pregnancy, I don’t worry whether or not your baby’s head is engaged until the end of pregnancy (36 weeks onwards). Engagement from 36 weeks is a positive sign that labour could start soon, and that you will have a good labour. Your baby’s head will usually remain engaged.
Before 36 weeks, the baby’s head can be engaged for a time and then not be engaged. This is because your baby is smaller so there is no reason why your baby’s head has to remain low in your pelvis.
Your baby’s head does not need to be engaged for you to go into labour. For the majority of women who have had a vaginal delivery, this is usually the case – the baby’s head is not engaged in the pelvis at the onset of labour.
If you are in your first ongoing pregnancy and your baby’s head remains high (not engaged) at 40 weeks, it is a concerning sign that you will go overdue and that your baby’s head may not fit easily through your birth canal during labour. It is suggestive of an occipito-posterior position (baby looking up rather than down) and a more difficult and prolonged labour. It also indicates you are at greater risk of an obstructed labour so, if it appears your baby will not fit through your birth canal, a Caesarean section may be needed.
Close application of the foetal head to the cervix will also help the cervix to ripen for the onset of labour. Alternatively, if the foetal head is high and not well applied to the cervix then it is more likely for a woman to go overdue with an unfavourable cervix.