A woman at 36 weeks gestation develops uterine contractions. Which of the following correctly describes the Ferguson reflex?
- A Cortisol from the fetal adrenal initiating parturition by suppressing progesterone production
- B Fetal head engagement compresses the maternal spinal cord, reflexly triggering uterine contractions
- C Prostaglandin release from the placenta in response to estrogen initiating the Ferguson reflex
- D Cervical and lower uterine segment distension activates stretch receptors → afferent neural signals to hypothalamus → neuroendocrine release of oxytocin from posterior pituitary → enhanced uterine contractions → more distension → positive feedback loop ✓
Explanation
The Ferguson reflex is a positive feedback neuroendocrine mechanism: mechanical distension of the cervix and lower uterine segment (by the presenting fetal part) activates mechanoreceptors that send afferent signals via pelvic nerves to the hypothalamus → stimulates oxytocin release from posterior pituitary → oxytocin causes stronger uterine contractions → more cervical dilation → more oxytocin release. This positive feedback amplifies labor. The reflex explains why oxytocin surges with crowning/delivery. Fetal cortisol contributes to initiation of labor (via CRH-driven processes), but that is a separate endocrine mechanism from the Ferguson reflex.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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Written and medically reviewed by the StethoPrep medical team.