Other primates also have a wider and straighter birth canal that allows a fetus to pass through more effectively. Modern human’s shorter upper extremities and evolution of bipedal locomotion may have placed a premium on assistance during labor. For this reason, researchers argue that assisted labor may have evolved with bipedalism. Obstructed labor has been documented as a complication of childbirth since the field of obstetrics originated. For over 1,000 years obstetricians have had to forcibly remove obstructed labor fetuses to prevent the death of the mother.Prior to the existence of the cesarean section, fetuses that were obstructed had a low survival rate. Even in the 21st century, if obstructed labor is left untreated, it could result in mother and infant death. Although surgical removal of the fetus is the preferred method of managing obstructed labor, manual removal using medical tools is also common.Obstructed labor is unique to humans compared to other primates. The evolution of humans to become obligate bipedal and increase in brain size create the problems associated with obstructed labor. In order for bipedal locomotion to be possible, many changes had to occur to the skeletal structure of humans, especially in the pelvis. Both the shape and orientation of the pelvis changed. Other primates have straighter and wider pelvises compared to humans. A narrow pelvis is better for bipedal locomotion but makes childbirth more difficult. The pelvis is sexually dimorphic, with females having a wider pelvis to be better suited for childbirth.
In Africa and Asia obstructed labor affects between two and five percent of deliveries. In 2015 about 6.5 million cases of obstructed labour or uterine rupture occurred. This resulted in 23,000 maternal deaths down from 29,000 deaths in 1990 (about 8% of all deaths related to pregnancy). It is also one of the leading causes of stillbirth. Most deaths due to this condition occur in the developing world. Cause
The main causes of obstructed labour include: a large or abnormally positioned baby, a small pelvis, and problems with the birth canal. Both the size and the position of the fetus can lead to obstructed labor. Abnormal positioning includes shoulder dystocia where the anterior shoulder does not pass easily below the pubic bone. A small pelvis of the mother can be a result of many factors. Risk factors for a small pelvis include malnutrition and a lack of exposure to sunlight causing vitamin D deficiency. A deficiency in calcium can also result in a small pelvis as the structures of the pelvic bones will be weak due to the lack of calcium. A relationship between maternal height and pelvis size is present and can be used to predict the possibility of obstructed labor. This relationship is a result of the mothers nutritional health throughout her life leading up to childbirth. Younger mothers are also at more risk for obstructed labor due to growth of the pelvis not being completed.