The majority of fetuses are in a breech presentation early in pregnancy. By week 38th week of gestation, however, the fetus normally turns to a cephalic presentation. Although the fetal head is the widest single diameter, the fetus’s buttocks [ breech], plus the lower extremities, actually takes up more space.
The fundus, being the largest part of the uterus, probably accounts for the fact that in approximately 97% of all pregnancies, the fetus turns so that the buttocks and lower extremities are in the fundus.
Vaginal delivery of a breech presentation requires great skill if the fetus is not to be damaged. With the low rate of vaginal breech deliveries in the developed world, experience is being lost. 6% of women with breech presentation still have a vaginal breech delivery as they present too late - so units need to retain a high level of preparedness.
Types of breech presentation:
I. Complete breech [ flexed breech]: The fetal attitude is one of complete flexion, with hips and knees both flexed and the feet tucked in beside the buttocks. The presenting part consists of two buttocks, external genitalia and two feet. It is commonly present in multiparae.
II. Incomplete breech: This is due to varying degrees of extension of thighs or legs at podalic pole. Three varieties are possible;
- Breech with extended legs [ frank breech ]: The breech presents with the hips flexed and legs extended on the abdomen. 70% of breech presentations are of this type and it is particularly common in primigravidae whose good uterine muscle tone inhibits flexion of the legs and free turning of the fetus.
- Footling breech: This is rare. One or both feet present because neither hips nor knees are fully flexed. The feet are lower than the buttocks, which distinguishes it from the complete breech.
- Knee presentation: This is very rare. Thighs are extended but the knees are flexed, bringing the knees down to present at the brim.