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Fetal position during pregnancy
Fetal position during pregnancy
As a fetus grows, it starts filling up the available space inside the uterus. Most fetuses spend some time lying sideways in the uterus. At 28 weeks' gestation, one in five of every fetuses are in the breech position (head up, buttocks down). Eventually, however - normally at around 36 weeks - the majority of babies finally settle with their head down toward the mother's vagina. When childbirth begins, the baby's head is first to emerge from the birth canal, followed by the rest of the body.
In a few cases, the fetus is not facing this way. This might lead to a complicated birth process and may pose risks to the baby and mother. In these cases, a caesarean section (C-section) may be considered to help deliver the baby.
If your baby has not settled into a headfirst position by week 32, follow-up is recommended. Around week 36, an ultrasound scan can check the fetal position and your doctor or midwife will explain the options for the final weeks of your pregnancy.
The chance of incorrect fetal positioning at birth may be increased in certain circumstances, including:
Methods for diagnosis
In more than 95% of births, the fetus's head is facing downward towards the mother's vagina. However, this can occur in several ways.
Occiput anterior (OA)
This is the most common and favourable birth position. The baby's head is down near the mother's vagina, with the face directed towards the mother's rear. Its head is also bent down, so the chin is resting against the chest and the feet are crossed.
Occiput posterior (OP)
The baby's head is down near the mother's vagina, but the face is directed towards the mother's front. In the weeks leading up to birth, 10-15% of fetuses are in this position, but most of them rotate their body shortly before birth and only 5-6% are born while in this position.    The OP position - also known as 'face up' or 'sunny-side up' - may cause a longer and more difficult labour.
Occiput transverse (OT)
The baby's head is down near the mother's vagina, with the face towards the mother's side. This is an uncommon position. Forceps or vacuum extraction can be used to rotate to assist birth, if required. A caesarean section may be performed in certain circumstances.
Face and brow presentations
In these rare presentations, the baby is in the normal OA position, but the baby's face is first to enter the birth canal rather than the top of the head. This is due to the chin pointing out rather than resting against the baby's chest. These presentations are usually discovered only once labour has started.
In the face presentation, which occurs once in every 800-900 births, the baby's entire face is first to enter the birth canal.      A vaginal examination at the start of labour will reveal this, as your doctor of midwife can feel the features of the face with their fingers. A baby in face presentation can be delivered normally, although there may be difficulties that may raise the need for a C-section. A baby born in face presentation can sometimes sustain bruises to the face, but these generally disappear shortly after birth.
In the brow presentation, which occurs once in every 750-1700 births, it is the baby's forehead that is first to enter the birth canal.        This can sometimes make for a more difficult labour and in some cases a C-section may be required.
Compound (or complex) presentation occurs less than once in every 400-1200 births.   In this presentation, a limb (usually an arm or hand) is lying near the birth canal alongside the head. This presentation requires extra care during labour, but the limb will usually slide back during the birth process.
About 3-4% of babies are in the breech position when labour starts.     The baby's buttocks are positioned down near the mother's vagina, while baby's head is facing upwards. There are several variations of the breech position:
- Frank breech - with legs straight up, feet near baby's face;
- Complete breech - with legs bent at the knees and crossed, and;
- Footling (Incomplete) breech - one or both of baby's feet are facing down, and will be the first to emerge from the birth canal.
Transverse (shoulder presentation)
In this position, the baby is lying sideways with its shoulder resting against the mother's pelvis. As noted above, most fetuses will lie sideways in the uterus at some point in the pregnancy. A fetus who maintains this position up to birth is a rare case, occurring only once in every 200-400 births.   
A baby in the transverse position at labour cannot be born by vaginal delivery; a C-section must be performed.
Umbilical cord presentation and cord prolapse
In uncommon cases (once every few hundred births), the umbilical cord may be the first to enter the birth canal, below the body (head or buttocks) of the baby. This can be a cause for concern, as the umbilical cord is the baby's lifeline. If the cord is under pressure and is blocked during delivery (normally by the baby's head passing through the birth canal), the baby could be in danger.
The difference between cord presentation and cord prolapse is in relation to when the waters break (when fetal membranes rupture). Cord presentation is when the cord enters the birth canal before the waters break. This gives your doctor time to plan for delivery. Cord prolapse is after the waters break and it is considered an emergency due to the risks to your baby. Most cord prolapses will require an urgent C-section.
Types of treatment
If your baby is still incorrectly positioned by the third trimester, some things can be done to guide them into the correct position. Some of these methods will only be performed by a medical professional, others you can try yourself, but it is highly advisable that you consult with your doctor beforehand.
Methods can include:
External cephalic version
External cephalic version (ECV) is a medical procedure and can be attempted between 32-37 weeks of pregnancy. Your doctor will place their hands over your abdomen, with one hand over your baby's head and the other on its buttocks, and coax the baby's body toward the correct position. Your doctor will monitor the baby's heart rate using a fetal heart rate monitor, and will often use ultrasound to get a clear picture of the fetal position, the uterus and the amount of amniotic fluid in it.
If the baby is still in a non-optimal position when labour starts, there are several options your doctor or midwife can consider:
- Internal version - during labour, the birth canal expands and makes the uterus more accessible. Your doctor can then reach inside and attempt to reposition the baby headfirst;
- Breech birth - this can be a safe procedure under certain conditions. If the baby is healthy and full-term, the mother's pelvis is wide and the labour normal, breech birth can be considered, and;
- Caesarean section - if the baby is still maintaining an incorrect posture and breech birth is not recommended, a caesarean section will most often be performed.