The Ferguson reflex is a birth reflex triggered by receptors in the vagina and cervix. Once the fetus presses on the organs, the cells mediate a release of the hormone oxytocin, which induces labor. If there are lesions in the spinal cord, this reflex may be abolished or diminished.
What is the Ferguson reflex?
The Ferguson reflex is a birth reflex triggered by receptors in the vagina and cervix. The reflex induces labor through oxytocin release. Mechanoreceptors of the sense of touch register touch by binding to pressure and stretch stimuli. Mechanoreceptors and their subtype of stretch receptors are located in the skin, where they are responsible for exteroception of stimuli from the environment. The receptors can also perform interoceptive tasks and thus bind to stretch and pressure stimuli from their own bodies. For this reason, stretch receptors are located in many human organs. They are mainly found in organs where measurements of tissue tension are necessary, such as the blood vessels or the lungs. Stretch receptors are also found in the cervix and vagina of women. These sensory cells are particularly relevant to the process of childbirth. They trigger the so-called Ferguson reflex as soon as they register the pressure of the descending child inside. The reflex was first described by the Canadian Ferguson in the 20th century. A reflex is always an unconscious and automatic bodily response to a particular stimulus. In the case of the Ferguson reflex, the stretch stimulus to the stretch receptors in the vagina and cervix triggers the release of oxytocin. This is a hormone that triggers labor and additionally influences social interaction.
Function and task
Stretch receptors are mechanoreceptors that respond to stimuli of stretch and tissue elongation by depolarization. These stretch receptors are located in the uterus and vagina, among other places, where they sense infant pressure during the birthing process. The sensory cells bind to the mechanical pressure stimuli and translate these stimuli into the language of the central nervous system. As a bioelectrical excitation, the stimulus travels down the spinal cord to the woman’s diencephalon. In a reflex response to the pressure stimuli, the diencephalon triggers the release of the hormone oxytocin. The uterus carries receptors for this hormone, to which the hormone binds, triggering a reflex response. This reflex is known as the Ferguson reflex and corresponds to what is called an intrinsic reflex. Thus, the effectors and affectors of the reflex circuit are located in the same organ, namely the uterus. The reflex initiates labor through the release of oxytocin. After the release of oxytocin, the uterine muscles are stimulated to contract. Finally, these contractions induce labor. The initiation of labor by the oxytocin also increases the pressure on the receptors so that the Ferguson reflex becomes a loop, leading to the release of oxytocin again and again until the baby is born. In this way, sensory information about the mechanical stretching of the cervix travels again and again to the discharging neurons of the hypothalamus, and the level of oxytocin in the mother’s blood continues to rise. The hormone oxytocin, in addition to the Ferguson reflex, also plays a crucial role in breastfeeding. The milk injection reflex, for example, is controlled by the oxytocin concentration in the mother’s blood. During and also after birth, the hormone also causes a decrease in cortisol. This effect improves the mother’s mood, strengthens the emotional bond with the child, and reduces perceived birth stress.
Illness and discomfort
In obstetrics, it may be necessary to induce a woman’s labor artificially, such as when the Ferguson reflex fails. This artificial induction of labor usually consists of the administration of oxytocin. In this way, the Ferguson reflex is artificially imitated. Its outcome and thus the hormone concentration in the mother’s blood are mimicked externally until labor is induced. There is controversy about the extent to which peridural anesthesia during labor affects oxytocin release. Peridural anesthesia is a central line anesthesia given through a cannula or with the help of a catheter into the spine.A local anesthetic or an opioid analgesic is usually administered. With peridural anesthesia, the woman feels less pain during childbirth because the pain sensation of the nerves in the peridural space of the spine is switched off. Since the Ferguson reflex is also triggered by the nerves of the spinal column, an impairment of the reflex under peridural anesthesia is obvious. Therefore, it is suspected that peridural anesthesia has a negative effect on the concentration of oxytocin in the mother’s blood. A low concentration of oxytocin not only causes a delay in labor, but additionally a high level of cortisol. This could increase birth stress for the mother under peridural anesthesia. Medical science has not yet reached a consensus on the relationships between peridural anesthesia, the Ferguson reflex, and birth stress. However, the described negative correlations are conceivable. Traumatic or other types of injury to the reflex-involved nerve pathways in the spinal cord also have a negative effect on the Ferguson reflex. For example, neurological diseases such as multiple sclerosis can cause inflammatory lesions in the reflex-mediating pathways that cause the nerves to conduct more slowly or even to shut down completely. Such associations can, in some circumstances, cause complications in childbirth that require artificial induction of labor or cesarean section.
