Which hormone coordinates uterine contraction after delivery?

IGIMS Staff Nurse - 2018

Obstetrics & Gynaecology

Easy

Appeared in: IGIMS Staff Nurse - 2018

Explanation

Oxytocin, a hormone released by the posterior pituitary gland, is the principal agent that stimulates strong, rhythmic contractions of the uterine muscle after delivery.
These contractions are crucial for compressing the blood vessels at the placental implantation site, which prevents postpartum hemorrhage.
Oxytocin also facilitates uterine involution, the process by which the uterus returns to its non-pregnant size.
The act of suckling during breastfeeding triggers a neurogenic reflex that increases oxytocin secretion, thereby enhancing uterine contractions and promoting the milk ejection (let-down) reflex.

Option A: Progesterone's primary role during pregnancy is to relax the uterine smooth muscle, thereby preventing contractions and maintaining the pregnancy. Its levels fall sharply after delivery, which is a prerequisite for contractions to begin.
Option C: Prolactin is the key hormone for stimulating milk production (lactogenesis) in the breast alveoli. It does not have a direct role in causing uterine contractions.
Option D: Estrogen's role is to promote the growth of the uterus during pregnancy and to increase the number of oxytocin receptors on the myometrium, which sensitizes the uterus to oxytocin. However, it is not the primary trigger for postpartum contractions.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain This question tests knowledge of the hormonal control of the uterus in the immediate postpartum period, specifically focusing on the mechanism of uterine contraction and involution as background academic context rather than a clinical decision trigger.
Nurses frequently administer synthetic oxytocin (Pitocin) intravenously after delivery to augment uterine contractions and prevent or treat postpartum hemorrhage from uterine atony.
A critical postpartum nursing assessment is checking the uterine fundus. A firm fundus indicates effective contraction, while a boggy (soft) uterus signifies atony and requires immediate fundal massage to prevent hemorrhage.
Encouraging early and frequent breastfeeding is a vital nursing intervention, as the suckling stimulus promotes natural oxytocin release, which aids uterine involution and reduces bleeding.

How to Approach the Question

First, identify the key phrase in the question: 'coordinates uterine contraction after delivery'.
Next, review the functions of the hormones listed in the options in the context of pregnancy and the postpartum period.
Recall that Progesterone is the 'pro-gestation' hormone that keeps the uterus relaxed.
Remember that Prolactin is for 'pro-lactation', meaning milk production.
Consider Estrogen's role in uterine growth and preparing the uterus for labor by increasing receptors, but not as the primary contractile agent.
Finally, associate Oxytocin with its well-known role in causing contractions during labor and after birth, as well as the milk let-down reflex. This makes it the correct choice.

Concept Tested & Keywords

Concept Tested: This question tests knowledge of the hormonal control of the uterus in the immediate postpartum period, specifically focusing on the mechanism of uterine contraction and involution.
Stem keywords: hormone, uterine contraction, after delivery
Lead-in keywords: Which
Negative lead-in flag: false

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E6 Physiology Guyton 4SAE Part 3 p. 65-67

E6 Obstetrics Williams p. 48-68