Most babies are born occiput anterior (OA) — facing their mother's back. When a baby faces forward instead, this is called occiput posterior (OP) or 'sunny-side up' and it can make labour significantly harder.
What Occiput Posterior Means
In OA position, the baby's occiput (back of the head) faces forward toward the mother's pubic bone and the baby faces the mother's back. This is the ideal position because the widest part of the head is aligned with the widest part of the pelvis.
In OP position, the baby faces the mother's front. The back of the head presses against the mother's sacrum, and the presenting diameter — the part of the head that leads into the pelvis — is slightly larger. This is what causes the characteristic back pain.
How OP Affects Labour
| OP Effect | Why It Happens |
|---|---|
| Intense back pain (back labour) | Baby's skull presses on sacrum with every contraction |
| Longer active labour | Less efficient cervical dilation |
| More frequent need for augmentation | Labour may stall |
| Higher instrumental delivery rate | Forceps or vacuum often needed for delivery |
| Baby may rotate during labour | 50–70% of OP babies rotate to OA spontaneously |
How to Encourage Your Baby to Rotate
- Hands-and-knees position — takes baby's weight off sacrum and allows rotation
- Slow dancing and swaying during early labour
- Avoid semi-recumbent position (reclining in bed) — it encourages OP
- Lunge walks during contractions — opens pelvis asymmetrically
- Epidural can relax pelvic floor, sometimes allowing rotation
Delivery Options for OP Babies
Many OP babies rotate spontaneously to OA just before crowning. Others are born in the OP position — this is entirely possible vaginally but may require additional pushing and sometimes instrumental assistance. C-section is not automatically required for an OP baby.
Tip
If you are told your baby is OP in the third trimester, spending 20–30 minutes a day in hands-and-knees position may encourage rotation before labour even begins.