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D3.1.19 (HL)—Hormonal control

Hormonal control of reproduction includes feedback in the menstrual cycle, progesterone support during pregnancy and oxytocin positive feedback during birth.

Syllabus
First assessment 2025
Objective
D3.1.19
Level
HL

Exam analysis

Chance of appearing5%of analysed past papers
Latest appearanceNovember 2024
Most common paperPaper1
Typical marks1

Common command terms

  • Identify
  • Describe

Scoring notes

Common mistake
Confusing positive oxytocin feedback in childbirth with negative feedback in the menstrual cycle.

Recent exam appearances

November 2024Paper1 ["HL"] · TZ040[ 1 ]D3.1.19 (HL)—Hormonal control
May 2023Paper2 ["HL"] · TZ16(c)[ 7 ]D3.1.19 (HL)—Hormonal control
November 2018Paper1 ["HL"] · TZ040[ 1 ]D3.1.19 (HL)—Hormonal control
May 2017Paper1 ["HL"] · TZ138[ 1 ]D3.1.19 (HL)—Hormonal control
November 2014Paper1 ["HL"] · TZ040[ 1 ]D3.1.19 (HL)—Hormonal control
Practice this objective

Coverage 2014–2024 · Updated 16 Jul 2026

Progesterone Maintains Pregnancy; Oxytocin Drives Birth

HL only

Progesterone maintains pregnancy, whereas its decrease near childbirth permits an oxytocin-driven positive-feedback loop of uterine contractions.

After implantation, hCG maintains the corpus luteum so it continues secreting progesterone. Later the placenta becomes the main progesterone source, maintaining the endometrium and reducing uterine contractions.

Near childbirth, progesterone levels fall. Cervical stretch promotes oxytocin release; oxytocin strengthens uterine contractions, which increase cervical stretch and cause still more oxytocin release.

Corpus luteum progesterone → placental progesterone → progesterone falls → contractions/stretch → oxytocin ↑ → stronger contractions → more stretch.

Positive feedback applies to the escalating childbirth loop; pregnancy maintenance is continuity through progesterone, not an LH-surge mechanism from the ovarian cycle.

Hormonal control

HL only

Assessment in practice

1 marks
How it is assessed

This objective is assessed through structured response, commonly using Identify / Describe.

Command terms

Identify / Describe

What earns marks

Build the answer around this relationship: Oxytocin uses positive feedback to intensify uterine contractions during birth.

Watch for

Confusing positive oxytocin feedback in childbirth with negative feedback in the menstrual cycle.

Representative question

Question 1

[Maximum number: 7]

Describe the hormone feedback mechanisms that help to prepare a woman's body for pregnancy, sustain the pregnancy and then give birth.

Retrieve the HL Reproduction Route

HL only

HL D3.1 is about ordered mechanisms and evidence judgment: endocrine control, gametogenesis contrast, one-sperm fertilization, early embryo stages, hCG detection, placental exchange, birth feedback, and HRT evaluation.

  • GnRH drives pituitary FSH/LH and sex-hormone production
  • spermatogenesis gives four sperm; oogenesis gives one ovum and polar bodies
  • acrosome entry, cortical block, cleavage, blastocyst, endometrium
  • hCG, placenta, childbirth feedback, and HRT risk-benefit evaluation

HL Human Reproduction

HL only

HL D3.1 moves from reproductive events into control and evidence. The strongest answers keep sequences in order: endocrine axis at puberty, gametogenesis outcomes, fertilization blocks, blastocyst implantation, hCG testing, placental exchange, childbirth feedback, and HRT evaluation.

  • Explain HL mechanisms in order, especially hormone pathways and early-development stages.
  • Compare gametogenesis and fertilization mechanisms using precise structural terms.
  • Evaluate HRT by weighing symptom benefits against risks and evidence quality.

Concept essentials

  • Oxytocin uses positive feedback to intensify uterine contractions during birth.
  • Progesterone maintains the endometrium and helps inhibit uterine contractions.
  • The placenta later produces sufficient hormones to sustain pregnancy.