Presentation & Position of the Foetus

The foetus' presentation and position affect how the foetus passes through the vagina. Most normal births involve a combination of vertex presentation with anterior position.

1. Presentation refers to how the foetus is situated in the uterus, while the part of foetus that is closest to the cervix is termed the presenting part. There are a few different types of presentation:

• Vertex or cephalic presentation . The most common and safest birth position where the baby's head is the presenting part.
• Transverse lie or shoulder presentation . Here a caesarean section is always needed.
• Breech , where the baby's buttocks presents first. Accounting for about 3 to 4% of all deliveries, the breech birth often involves a longer labour due to the fact that the buttocks does not as easily open the cervix as the head. Various types of breech exist. These include: complete breech is which the baby sits cross legged at the bottom of your uterus; a frank breech, where the baby crosses its legs straight up with his feet near the face; and a footing breech, where one or both of the baby's feet present first; very uncommon form is the knee breech where the baby's knee presents before the foot.

A breech presentation may not be discovered until after labour has begun, but where there are no other complications (such as a prolapsed cord) a vaginal birth is possible. However forceps or a vacuum extractor may be required. Where a breech presentation or transverse lie position is discovered during pregnancy, it may be possible to rotate the baby to an upright or vertex position using a procedure called external version . Performed under the guidance of ultrasound , the physician manipulates the baby into a head-down position by applying gentle, but firm pressure to the baby's head and hip through your abdomen. This procedure is generally most successful if it's performed at 36 weeks due to the fact that after 37 weeks less amniotic fluid makes it tougher to rotate the baby. However, there are risks, including inducing labour , producing pain in the abdomen, and although very rare, the risk of shearing the placenta from the uterine wall also exists.

2. The position of the baby refers to the direction that the foetus is facing. Most commonly the baby's position is anterior , where the back of the head is touching the abdomen wall. The less common posterior position is where the back of the baby's head is against the spine. However, most posterior babies rotate to an interior position before the second stage of labour .

Where there is difficulty in delivery due to abnormal presentation and/or position, and the vaginal opening isn't stretching enough to let the baby emerge and a tear is likely, a doctor may perform an episiotomy .

The information in this page is presented in summarised form and has been taken from the following source(s):
1. Bayfront's Health Adventure, A Woman's Way to Health: http://www.bayfront.org/