State from where do the signals for parturition originate in human females.

Question

Q. State from where do the signals for parturition originate in human females.

CBSECBSE Class XII Board 2019Subjective· 1mImportance★★★★★

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Concept understanding — Parturition Hormonal Control

Let’s begin with something you already know. When a baby is ready to be born, the mother’s body doesn’t just “decide” one day — it follows a precise, hormone-driven sequence. Think of it like a carefully timed relay race: one hormone passes the baton to the next, and each step triggers the next until labour begins.

The everyday intuition

Imagine you are waiting for a train. The station master doesn’t just blow the whistle randomly. First, the train arrives at the platform, then the guard checks the signal, then the whistle blows, and only then does the train move. Parturition — the process of giving birth — works the same way. The baby’s body sends the first signal, the mother’s body receives it, and a chain of hormonal commands follows. No signal, no movement.

What parturition means

Parturition is the medical term for childbirth — the expulsion of the fully developed baby from the mother’s uterus. In NCERT Class 12 Biology (Chapter: Human Reproduction), it is described as the process that begins with the onset of labour and ends with the delivery of the baby and the placenta.

The key point: parturition is not a sudden event. It is the climax of a hormonal cascade that starts weeks earlier.

The hormonal relay: step by step

The entire process is controlled by a feedback loop between the baby’s brain, the mother’s hypothalamus, and her uterus. Here is the sequence as NCERT presents it:

The baby’s brain starts it. As the foetus grows, its hypothalamus matures and releases corticotropin-releasing hormone (CRH). This hormone travels to the foetal pituitary gland.
Foetal pituitary secretes ACTH. ACTH (adrenocorticotropic hormone) stimulates the foetal adrenal glands to produce cortisol.
Cortisol from the foetus acts on the placenta. The placenta, which connects mother and baby, responds by producing oestrogen in increasing amounts. At the same time, progesterone levels fall.

Important

The shift from high progesterone to high oestrogen is the critical switch. Progesterone keeps the uterus relaxed (quiet). Oestrogen makes the uterine muscle sensitive to contraction signals. Without this shift, labour cannot begin.

Oestrogen stimulates the uterus to produce oxytocin receptors. The mother’s posterior pituitary gland also releases oxytocin — the hormone that causes strong, rhythmic contractions of the uterine muscles.
Oxytocin creates a positive feedback loop. Each contraction pushes the baby’s head against the cervix. This stretching of the cervix sends nerve signals back to the mother’s brain, which releases more oxytocin. More oxytocin → stronger contractions → more stretching → even more oxytocin. This cycle continues until the baby is delivered.

Why this matters

It explains why labour cannot be induced artificially without medical intervention — the baby’s own hormones must first signal readiness.
It also explains why stress or illness in the mother can delay labour: if the foetal cortisol signal is weak, the oestrogen shift may not happen on time.
In some cases, doctors use synthetic oxytocin (Pitocin) to start or strengthen labour — this mimics the natural hormone.

A quick summary of the key hormones

Hormone	Source	Role in parturition
CRH	Foetal hypothalamus	Starts the cascade
ACTH	Foetal pituitary	Stimulates foetal adrenal glands
Cortisol	Foetal adrenal glands	Triggers placental oestrogen production
Oestrogen	Placenta	Makes uterus sensitive to oxytocin
Oxytocin	Mother’s posterior pituitary	Causes uterine contractions
Progesterone	Placenta (early)	Keeps uterus relaxed; falls before labour

Note

NCERT does not require you to memorise every hormone name for a prose exam — but you must understand the sequence: baby’s brain → foetal cortisol → placental oestrogen → maternal oxytocin → contractions. That is the core logic.

One final point

Parturition is not just a biological event — it is the only process in the human body where a positive feedback loop (not negative feedback) is the normal, healthy mechanism. Most body systems work to reduce change (like temperature regulation). Here, the body amplifies change until the goal is reached. That is why labour, once started, usually continues to completion.

So when you think of parturition, remember the relay: the baby passes the first baton, and the mother’s body runs the rest of the race.

On search engines, students preparing for exams frequently type in "Parturition Hormonal Control class 12 biology", "Parturition Hormonal Control: Definition, Diagram & Examples", or "Parturition Hormonal Control NEET questions". This concept is directly part of the Human Reproduction chapter in the NCERT/CBSE Class 12 Biology syllabus, and it is also an important topic for NEET and state medical/CET entrance exams, making it worth mastering for both board and competitive-exam preparation.

The signals for parturition (childbirth) originate from the fully developed foetus and the placenta together, which trigger a hormonal cascade ending in childbirth.

In human females, the process of parturition — the act of giving birth — is not a sudden, random event. It is a precisely timed physiological event, and the initiating signals come jointly from the fully developed foetus and the placenta. By the end of pregnancy the foetus is mature, and the placenta itself begins to shift its own hormone output.

Specifically, the placenta reduces its secretion of progesterone — the hormone that had been keeping the uterine muscle relaxed and quiet throughout pregnancy — and increases its secretion of oestrogens.

Note

Progesterone is often called the "pregnancy-maintaining hormone" because it inhibits uterine contractions. A drop in its level is essential for labour to begin.

The rising oestrogen levels have two critical effects. First, they make the uterine muscle (myometrium) more sensitive to oxytocin, a powerful hormone that stimulates contractions. Second, oestrogen stimulates the placenta and foetal membranes to produce prostaglandins, which further help ripen the cervix and strengthen the mild initial uterine contractions — together these mild contractions constitute what is called the foetal ejection reflex.

This mild contraction triggers a reflex — the neuroendocrine reflex — that signals the mother's posterior pituitary gland to release a surge of oxytocin into her bloodstream. This oxytocin then acts on the uterus, causing stronger and more frequent contractions. These stronger contractions push the foetus further, stretching the cervix more, which in turn signals for even more oxytocin release.

Important

This self-amplifying cycle — uterine contraction → cervical stretch → oxytocin release → stronger contraction — is called a positive feedback loop. It is the driving force that continues until the baby is delivered.

So, the initiating signals for parturition come jointly from the fully developed foetus and the placenta, which together set off this hormonal cascade; the mother's body then provides the machinery (oxytocin-driven contractions) for the final delivery.

✓Final answer

The signals for parturition originate from the fully developed foetus and the placenta together. These trigger mild uterine contractions (the foetal ejection reflex) via a shift in the placenta's oestrogen-to-progesterone output and prostaglandin release, which stimulate oxytocin release from the mother's pituitary, setting up a positive feedback loop of stronger contractions that continues until delivery.

Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

Showing the 12 most recent of 21 on this concept.

CBSE 2026Set 57/3/11 markMCQ
$Q. Foetal ejection reflex in human female triggers the release of which hormone ? (A) Oxytocin from foetal pituitary gland (B) hCG from placenta (C) Progesterone from corpus luteum (D) Oxytocin from maternal pituitary gland$
›Reveal solutionSolution

The foetal ejection reflex triggers the release of oxytocin from the maternal pituitary gland, which then drives uterine contractions during childbirth.

The foetal ejection reflex is a beautifully coordinated physiological event that marks the final stage of pregnancy. When the baby's head presses against the cervix and vaginal walls, sensory nerve impulses travel from the cervix to the hypothalamus in the mother's brain. This neural signal is the trigger — it tells the posterior pituitary gland to release oxytocin into the mother's bloodstream.

Oxytocin is the key hormone here. It acts directly on the smooth muscles of the uterus, making them contract more strongly. These contractions push the baby further down, which stretches the cervix even more, which in turn signals the release of even more oxytocin. This is a classic positive feedback loop — the more the uterus contracts, the more oxytocin is released, and the stronger the contractions become. The cycle continues until the baby is delivered.

Important

The oxytocin that drives this process comes from the mother's posterior pituitary gland, not from the foetus. The foetal pituitary is not involved in this reflex.

Now look at the options carefully. Option (A) says oxytocin from the foetal pituitary — that is incorrect because the foetus does not release oxytocin to trigger labour. Option (B) mentions hCG from the placenta — hCG is crucial in early pregnancy for maintaining the corpus luteum, but it has no role in the foetal ejection reflex. Option (C) says progesterone from the corpus luteum — progesterone actually keeps the uterus quiet during pregnancy; its levels fall before labour begins, so it does not trigger contractions. Option (D) is the correct one: oxytocin from the maternal pituitary gland.

Note

Synthetic oxytocin (Pitocin) is sometimes given to induce or speed up labour in hospitals — it mimics the natural hormone released by the mother's pituitary.

The NCERT textbook for Class 12 Biology (Chapter 3: Human Reproduction) explicitly states: "The signals for parturition originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex. This reflex triggers release of oxytocin from the maternal pituitary." So the source is clearly the mother's pituitary, not the foetus's.

✓Final answer
$The foetal ejection reflex triggers the release of oxytocin from the maternal pituitary gland (Option D).$
CBSE 2026Set V11 mark
$Q. The initial few days of milk produced after parturition is ___________.$
›Reveal solutionSolution

The first milk secreted after childbirth is colostrum.

The milk produced by the mammary glands during the initial few days after parturition (childbirth) is called colostrum. It is yellowish, and is rich in antibodies (especially IgA) that provide essential passive immunity to the newborn infant. It is therefore very important that the newborn is fed on this first milk.

✓Final answer
$Colostrum$
CBSE 2026Set ANNUAL1 markMCQ
$Q. Which hormone is involved to induce parturition?$
(a) Prolactin
(b) Adrenaline
(c) Oxytocin
(d) Progesterone
›Reveal solutionSolution

Parturition (delivery) is induced by a neuro-endocrine reflex in which the posterior pituitary hormone oxytocin causes powerful uterine contractions.

At the end of pregnancy, signals from the fully-developed foetus and the placenta induce mild uterine contractions called the 'foetal ejection reflex'. This triggers release of oxytocin from the maternal posterior pituitary, which acts on the uterine (myometrial) muscle causing strong contractions, which in turn stimulate further oxytocin release (a positive feedback loop) leading to expulsion of the baby. Progesterone, in contrast, MAINTAINS pregnancy by keeping the uterus quiescent; prolactin controls milk production; adrenaline is not involved.

✓Final answer
$(c) Oxytocin.$
CBSE 2026Set ANNUAL1 mark
$Q. The milk produced during the initial few days of lactation is called ________.$
›Reveal solutionSolution

The yellowish fluid secreted by the mammary glands during the first few days of lactation is called colostrum, and it is rich in antibodies (IgA) essential for building the newborn's immunity.

After parturition, the mammary glands of the mother start producing milk (lactation) under the stimulus of the hormone prolactin. The milk produced during the initial few days of lactation is called colostrum. Colostrum contains several antibodies (mainly Immunoglobulin A, IgA) that are absolutely essential for building the immune system (passive immunity) of the newborn infant, in addition to nutrients. This is one of the key reasons breastfeeding is recommended immediately after birth.

✓Final answer
$Colostrum — the antibody-rich milk secreted during the initial days of lactation.$
CBSE 2026Set ANNUAL1 mark
$Q. Why is mother's milk considered very essential for the new-born infants?$
›Reveal solutionSolution

Mother's milk (colostrum) supplies antibodies (IgA) for passive immunity plus complete nutrition, protecting the newborn.

The milk produced during the initial few days of lactation is called colostrum. It is yellowish and contains several antibodies, chiefly immunoglobulin A (IgA). Since the newborn's own immune system is not yet developed, these maternal antibodies provide passive immunity that protects the infant against infections.

Breast milk is also nutritionally complete and easily digestible, supplying the right balance of proteins, fats, sugars and minerals for the baby. For both these reasons — immunity and nutrition — breast-feeding of the newborn is strongly recommended.

✓Final answer
$It provides antibodies (IgA in colostrum) that confer passive immunity and gives complete, easily digestible nutrition to the newborn.$
CBSE 2025Set X11 mark
$Q.____________ acts on uterine muscle and cause stronger contractions during parturition.$
›Reveal solutionSolution

Oxytocin causes strong uterine contractions during childbirth.

Oxytocin, released from the posterior pituitary, acts on the smooth muscles of the uterus and causes stronger contractions during parturition (childbirth). A vigorous positive feedback loop (foetal ejection reflex) between uterine contractions and oxytocin secretion leads to expulsion of the baby.

✓Final answer
$Oxytocin$
CBSE 2025Set A1 mark
$Q. Answer in one word / sentence: What is Colostrum?$
›Reveal solutionSolution

Colostrum is the first milk produced after childbirth, rich in maternal antibodies that protect the newborn.

During the initial days of lactation, the mammary glands secrete a special milk called colostrum. It is yellowish and thick, and importantly contains a high concentration of immunoglobulins (mainly IgA) along with other nutrients. These maternal antibodies passed to the infant through colostrum provide passive immunity, helping protect the newborn from infections until its own immune system matures. This is why breastfeeding (and specifically colostrum) is strongly recommended immediately after birth.

✓Final answer
$Colostrum — the antibody-rich first milk secreted during the initial days of lactation.$
CBSE 2025Set ANNUAL1 mark
$Q. Define parturition.$
›Reveal solutionSolution

Parturition is the hormonally triggered process of childbirth, marking the end of gestation.

Parturition refers to the process of delivery of the fully developed foetus (and, subsequently, the placenta) from the uterus, marking the end of a full-term pregnancy (about 9 months/40 weeks in humans). It is induced by complex neuroendocrine signals, involving mild uterine contractions (Ferguson's reflex) initiated by signals from the fully developed foetus and the placenta, which stimulate release of the hormone oxytocin from the mother's pituitary; oxytocin acts on the uterine muscle to cause strong contractions, leading to expulsion of the baby.

✓Final answer
$Parturition is the process of delivery/childbirth — the expulsion of the fully developed foetus (and later the placenta) from the mother's uterus at the end of gestation.$
CBSE 2024Set A11 mark
$Q. The hormone which helps in Parturition is ____________.$
›Reveal solutionSolution

Oxytocin triggers the vigorous uterine contractions that cause parturition (childbirth).

Parturition is the process of delivery of the foetus. It is induced by a complex neuroendocrine mechanism: signals from the fully developed foetus and placenta trigger the release of oxytocin from the maternal pituitary. Oxytocin acts on the uterine smooth muscle, causing strong contractions that expel the baby.

✓Final answer
$Oxytocin$
CBSE 2024Set ANNUAL1 mark
$Q. Why is colostrum very much essential for new born infants?$
›Reveal solutionSolution

Colostrum provides the newborn with maternal antibodies and nutrients critical for building the infant's early immune defence.

Colostrum is the thick, yellowish milk secreted by the mammary glands during the first few days after parturition, before regular/mature milk production begins. It is especially rich in immunoglobulins, particularly IgA (secretory antibodies), which the infant's own immune system cannot yet produce in adequate amounts. These maternal antibodies pass into the infant's gut and confer passive immunity, protecting the newborn against various infections during the vulnerable early period of life when its own immune system is still immature. Colostrum is also nutritionally dense.

✓Final answer
$It transfers maternal antibodies (mainly IgA) that give the newborn passive immunity against infections while its own immune system matures.$
CBSE 2024Set ANNUAL1 markMCQ
$Q. The yellowish fluid colostrum secreted by mother during the initial days of lactation has antibodies$
(a) Ig E
(b) Ig A
(c) Ig M
(d) Ig G
›Reveal solutionSolution

Colostrum's protective antibodies are predominantly IgA, giving the newborn passive mucosal immunity.

Colostrum, the thick yellowish fluid secreted by the mammary glands during the first few days after childbirth (before regular breast milk is produced), is especially rich in Immunoglobulin A (IgA) antibodies. IgA is well suited to protect mucosal surfaces (like the infant's gut lining), providing the newborn with essential passive immunity against various infections during its earliest and most vulnerable days, since the baby's own adaptive immune system is still immature. This is one of the key reasons doctors recommend that every newborn be fed colostrum.

✓Final answer
$(b) Ig A$
CBSE 2023Set ANNUAL1 mark
$Q. What is foetal ejection reflex?$
›Reveal solutionSolution

A positive-feedback hormonal reflex, triggered near full term, that initiates labour and childbirth.

Towards the end of pregnancy (around nine months), signals originating from the fully developed foetus and the placenta bring about mild contractions of the uterus, referred to as the foetal ejection reflex. This reflex induces the release of the hormone oxytocin from the maternal pituitary gland. Oxytocin acts on the uterine (myometrial) smooth muscle, causing strong contractions of the uterus, which in turn stimulates still more oxytocin release — a self-reinforcing positive-feedback loop. This progressively intensifying cycle of contractions ultimately leads to expulsion of the foetus through the birth canal, i.e., parturition (childbirth).

✓Final answer
$A positive-feedback reflex, near full term, in which mild uterine contractions trigger oxytocin release, which causes stronger contractions and yet more oxytocin release, culminating in expulsion of the foetus (parturition).$

Q.State from where do the signals for parturition originate in human females.

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