The Ferguson reflex (also called the fetal ejection reflex) is the neuroendocrine reflex comprising the self-sustaining cycle of uterine contractions initiated by pressure at the

cervix The cervix or cervix uteri (Latin, 'neck of the uterus') is the lower part of the uterus (womb) in the human female reproductive system. The cervix is usually 2 to 3 cm long (~1 inch) and roughly cylindrical in shape, which changes during ...

, more precisely, the internal end of cervix, or vaginal walls. It is an example of

positive feedback Positive feedback (exacerbating feedback, self-reinforcing feedback) is a process that occurs in a feedback loop which exacerbates the effects of a small disturbance. That is, the effects of a perturbation on a system include an increase in th ...

in biology. The Ferguson reflex occurs in mammals.

Mechanism

Upon application of pressure to the internal end of the cervix,

oxytocin Oxytocin (Oxt or OT) is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. It plays a role in social bonding, reproduction, childbirth, and the period after childbirth. Oxytoc ...

is released (therefore increase in contractile proteins), which stimulates uterine contractions, which in turn increases pressure on the cervix (thereby increasing oxytocin release, etc.), until the baby is delivered. Sensory information regarding mechanical stretch of the cervix is carried in a sensory neuron, which synapses in the dorsal horn before ascending to the brain in the anterolateral columns (ipsilateral and contralateral routes). Via the medial forebrain bundle, the efferent reaches the PVN and

SON A son is a male offspring; a boy or a man in relation to his parents. The female counterpart is a daughter. From a biological perspective, a son constitutes a first degree relative. Social issues In pre-industrial societies and some curren ...

of the

hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus ...

. The

posterior pituitary The posterior pituitary (or neurohypophysis) is the posterior lobe of the pituitary gland which is part of the endocrine system. The posterior pituitary is not glandular as is the anterior pituitary. Instead, it is largely a collection of axonal ...

releases oxytocin due to increased firing in the hypothalamo-hypophyseal tract. Oxytocin acts on the

myometrium The myometrium is the middle layer of the uterine wall, consisting mainly of uterine smooth muscle cells (also called uterine myocytes) but also of supporting stromal and vascular tissue. Its main function is to induce uterine contractions. Struc ...

, on receptors which have been

upregulated In the biological context of organisms' production of gene products, downregulation is the process by which a cell decreases the quantity of a cellular component, such as RNA or protein, in response to an external stimulus. The complementary pro ...

by a functional increase of the estrogen-progesterone ratio. This functional ratio change is mediated by a decrease in myometrial sensitivity to progesterone, due to a decrease in

progesterone receptor A The progesterone receptor A (PR-A) is one of three known isoforms of the progesterone receptor (PR), the main biological target of the endogenous progestogen sex hormone progesterone. The other isoforms of the PR include the PR-B and PR-C. See a ...

, and a concurrent increase in myometrial sensitivity to estrogen, due to an increase in estrogen receptor α. This causes myometrial contraction and further positive feedback on the reflex. Studies among ewes demonstrated that the Ferguson reflex is blocked by epidural anesthesia. In their studies among mice, Niles Newton and colleagues demonstrated the importance of cortical influences.Newton N, Foshee D, Newton M. Experimental inhibition of labor through environmental disturbance. Obstetrics and Gynecology 1967; 371-377 They enlarged the topic by introducing the term ''fetus ejection reflex''. The concept of cortical influences provided reasons to raise questions about the process of parturition among humans, characterized by a high

encephalization quotient Encephalization quotient (EQ), encephalization level (EL), or just encephalization is a relative brain size measure that is defined as the ratio between observed to predicted brain mass for an animal of a given size, based on nonlinear regress ...

Michel Odent Michel Odent (born 1930) is a French obstetrician and childbirth specialist. Education Born in a French village in 1930, Odent studied medicine in Paris and was educated as a surgeon in the 1950s. He has been presented in Lancet as “one of the l ...

had observed that women can experience such a reflex, characterized by a birth after a short series of irresistible and powerful contractions without any room for voluntary movements, resulting in a painless birth. For such a hormonal cascade to occur requires sufficient psychological safety, as occurs in normal or undisturbed birth. The higher the intervention rate, such as induction or caesarian section, the lower the likelihood of the Ferguson Reflex occurring. In contrast, the lower the incidence of intervention, such as is found in thos
countries with high rate of home births
and birth centers worldwide, the higher the likelihood of the Ferguson Reflex occurring. This may explain the lack of research, considering the public health benefits of such education to both hospitals and the general public.

References

{{reflist Obstetrics Vagina Midwifery Childbirth Natural childbirth