When should my baby's head engage? If it engages early does that mean I am going to give birth early?

The BabyCentre Editorial Team answers:

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As your baby grows towards the end of pregnancy, the shape of your uterus, your liver and intestines encourage your baby's presenting part (usually head, but sometimes bottom) to dip down into the pelvic cavity. This can occur as early as 33 or 34 weeks, but may not happen before labour starts. If the baby engages in the pelvis early this does not mean that you will give birth early. Usually the baby will engage in the pelvis by 37 to 38 weeks, but this process can also be affected by lots of other things:

• If you are very sporty and have well-toned abdominal muscles this may mean that your tummy is held in tighter, which changes the angle of the baby's body and presenting part to the pelvic brim. In this position it is harder for your baby to engage in the pelvis. To encourage your baby's head to engage you need to relax your tummy muscles and "dangle your belly" out at the front.

• If you spend a lot of time sitting down at work, in a car, or in soft easy chairs to watch TV, your baby is likely to be lying in a posterior position - that is with its back to your back. In this position it is harder for your baby to enter your pelvis. This baby position is not the best position for an efficient labour, partly because the presenting part remains high for so long. Take care to sit leaning forward whenever you sit down, with your knees below your hips, which will help your baby turn its back towards your front and to move down. A kneeling chair is ideal for this.

• If you have had several babies before, your tummy muscles may be loose, which makes it easy for the baby to move and change position a lot. Sometimes your baby may not lie up and down (longitudinal), but across your tummy (transverse) or at an angle (oblique). Positions like these make it less likely that your baby will engage in the pelvis before the start of labour.

• Your baby may be a large one, in which case it may not descend into the pelvis until contractions start.

• The shape of your pelvis may also be relevant. Sometimes the pelvic inlet is narrow. In these cases it may take a long time for the baby's presenting part to enter the pelvis, but once it is in, birth is usually rapid, because the pelvic outlet in these cases tends to be roomy.