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The second stage of labour may be delayed or lengthy due to poor or uncoordinated uterine action, an abnormal uterine position such as breech or shoulder dystocia, and cephalopelvic disproportion (a small pelvis or large infant). Prolonged labour may result in maternal exhaustion, fetal distress, and other complications including obstetric fistula.
These labour contractions are characterized by their rhythmic tightening and relaxation of the myometrium, the most prominent uterine muscle. Labour contractions primarily serve the purpose of opening and dilating the cervix , [ 7 ] which leads to the assisting of the passage of the baby through the vaginal canal during the first stage of labour.
An induced vaginal delivery is a delivery involving labor induction, where drugs or manual techniques are used to initiate labor. [11] Vaginal delivery can be either spontaneous or induced. An assisted vaginal delivery ( AVD ) or instrumental vaginal delivery occurs when a pregnant woman requires the use of special instruments such as forceps ...
As the fetal hypothalamus matures, the activation of the hypothalamic–pituitary–adrenal (HPA) axis initiates labor through two hormonal mechanisms. The end pathway of both mechanisms lead to contractions in the myometrium, a mechanical cause of placental separation, which is due to the sheer force and contractile and involutive changes that occur within the uterus, distorting the placentome.
Pregnancy itself is a factor of hypercoagulability (pregnancy-induced hypercoagulability), as a physiologically adaptive mechanism to prevent postpartum bleeding. [165] However, in combination with an underlying hypercoagulable state, the risk of thrombosis or embolism may become substantial.
This elaborate mechanism of labor, which requires a constant readjustment of the fetal head in relation to the bony pelvis (and which may vary somewhat depending on the shape of the pelvis in question), is completely different from the obstetrical mechanics of the other higher primates whose infants generally drop through the pelvis without any ...
These are normal physiological adaptations that cause changes in behavior, the functioning of the heart, blood vessels, and blood, metabolism including increases in blood sugar levels, kidney function, posture, and breathing. During pregnancy numerous hormones and proteins are secreted that also have a broad range of effects.
An illustration of normal head-first presentation by the obstetrician William Smellie from about 1792. The membranes have ruptured and the cervix is fully dilated. Humans usually produce a single offspring at a time. The mother's body is prepared for birth by hormones produced by the pituitary gland, the ovary and the placenta. [2]