A malposition is commonly considered a "bad" (mal, from the French) position. Personally, I don't think the position of the posterior baby deserves such an unyielding judgement. Yet, for some posterior babies, their position is what prevents their birth. And that is bad, in a way of speaking.
Malposition is a harsh word meaning the baby's head is, either not coming into the pelvis first, or, tipped or turned in a way that is not best for molding, or shaping itself, to fit the pelvis.
Malposition is a term used in medical literature to mean:
- Posterior presentation
- A deflexed or extended fetal head, called a "military"presentation
- Oblique lie
- Transverse lie
When the head is at a difficult angle, especially when mother’s muscles or pelvic tendons are tight, hours or even days can be added to the length of labor.
Why do I use the word "malposition?"
Basically, if the position of the baby or the baby's head makes labor so challenging that either the baby can't be born or is so hard on the mother or baby to need medical care or special efforts for birthing, I'll use the word "malposition." Sorry that it sounds so judgemental and harsh. It's a hard choice to use the word, but its the word used in the fields of obstetrics and midwifery.
Please remember, some of these babies who are labeled as “malpositioned” are born with little trouble and no interventions!
To take a positive view, if the baby fits, whether posterior or breech, or even deflexed, without compromising the woman or her baby, then its a fine position for that baby. Babies get into the best position they can given the room they have in the uterus. See more on this, under 3 Principles in Pregnancy.