Mednotes

L9 RDA Contraception

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aliasesL9 RDA Contraception

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Overview

This lecture covers contraception from mechanism to consultation: how the menstrual cycle’s hormonal chain of command normally works, how each contraceptive class interrupts that chain (or a downstream reproductive step), the tiered efficacy of methods, and the practical framework for choosing a method with a patient, including a worked adolescent consultation scenario and the Gillick/Fraser criteria for consent.

Menstrual Cycle Physiology

  • Chain of command: hypothalamus releases GnRH → acts on the anterior pituitary → anterior pituitary releases gonadotrophins (FSH/LH) → act on the ovary → ovary secretes oestrogen (E) and progesterone (P) → act on the endometrium.
  • Ovarian cycle, in order: primordial follicles → primary follicles → secondary follicle → mature (Graafian) follicle → ovulation → corpus luteum → corpus albicans.
  • Follicular activity: a continuous trickle of follicles develops throughout the cycle; most are doomed to atresia; one or two are “rescued” by FSH and LH; the dominant antral follicle secretes high E at maturity and is converted to a preovulatory follicle by a transient LH surge; the successful ovulatory follicle forms a corpus luteum, which secretes P (and E) until luteolysis 14 days later.
  • Uterine (menstrual) cycle across days 1-28: menstrual phase → proliferative phase (driven by rising oestrogen) → ovulation → secretory phase (driven by progesterone and oestrogen) → menstruation restarts. The endometrium comprises the stratum functionalis and stratum basalis.
  • Endometrial actions:
    • Oestrogen (proliferative): stromal proliferation, thickening, oedema; ↑ number and size of glands; ↑ synthesis of progesterone receptors; ↑ elastic mucus.
    • Progesterone (secretory): drives a thick secretion rich in glycoprotein, sugars and amino acids, so mucus thickens and becomes impenetrable; antagonises oestrogen-driven growth and promotes differentiation; as E and P drop at the end of the luteal phase, the secretory epithelium collapses.
  • Feedback: for most of the cycle, oestrogen and progesterone feed back negatively on the pituitary and hypothalamus, decreasing gonadotrophin secretion. Around days 12-14, high oestrogen from the dominant follicle switches to positive feedback, triggering the LH surge and ovulation.

How Contraceptives Work

  • Combined (oestrogen + progesterone) and high-dose progesterone-only methods mimic negative feedback and suppress FSH/LH secretion → prevent the FSH rise that stimulates follicle development; without a rise in oestrogen there is no LH surge, so ovulation is suppressed. They also change cervical mucus and thin the endometrium.
  • Low-dose progesterone promotes thick cervical mucus that inhibits sperm movement, and thins the endometrium by opposing oestrogen’s action: a lag in glandular and stromal development leaves underdeveloped glands, with glandular atrophy occurring over time.
  • General framework: a contraceptive can block egg/sperm production, movement of sperm, ovulation, movement of the egg, fertilisation and movement of the fertilised egg to the uterus, or implantation.
    • Barriers and reversible hormonal methods (COC, Depo-Provera, levonorgestrel ECP - delays ovulation) block sperm movement and/or ovulation.
    • Vasectomy blocks sperm movement; tubal ligation blocks movement of the egg.
    • Copper IUD blocks sperm survival in ongoing use, or implantation when used post-coitally as emergency contraception.
    • All hormonal methods thicken cervical mucus and so block sperm motility: this is the main action of the Jadelle implant, the progesterone-only pill and the hormonal IUS, and a secondary (non-main) action of Depo-Provera and the COC.
    • No method covered blocks fertilisation itself or the fertilised egg’s movement to the uterus.

Efficacy and Tiers

  • Perfect use = consistent and correct use; typical use = as generally used, including inconsistent or incorrect use.
  • Tier 1 (failure rate <1%, typical close to perfect): implant, vasectomy, tubal ligation, copper IUD, hormonal IUS.
  • Tier 2: Depo-Provera injection, combined oral contraceptive (COC), progesterone-only pill (POP).
  • Tier 3 (typical failure rate >10%): condoms, withdrawal, fertility awareness.
  • First-year failure rates, perfect/typical use (%): implant 0.05/0.05, vasectomy 0.1/0.15, tubal sterilisation 0.5/0.5, copper IUD 0.6/0.8, hormonal IUD 0.2/0.2, injectable 0.2/6, vaginal ring 0.3/9, patch 0.3/9, pill 0.3/9, male condom 2/18, female condom 5/21, withdrawal 4/22, no method 85/85.

Guidelines and Medical Eligibility Criteria (MEC)

  • Key sources: New Zealand Aotearoa’s Guidance on Contraception (2020), FSRH, and the WHO medical eligibility criteria (app and summary chart).
  • MEC categories: MEC 1 = unrestricted use; MEC 2 = benefits outweigh risks; MEC 3 = risks generally outweigh benefits; MEC 4 = should not be used in any circumstances.

Tier 1: Long-Acting Reversible Contraceptives (LARCs)

  • Implant rod (Jadelle): failure rate 0.1% in the first 4 years; 5-year device; two progesterone-containing rods inserted subdermally into the inner upper arm; thickens cervical mucus, also thins the endometrium, sometimes stops ovulation; about 1/3 of users have prolonged or frequent bleeding.
  • Hormonal IUS (Mirena/Jaydess): Mirena 0.2% failure, approved for 8 years; Jaydess <1% failure, approved for 3 years; low-dose progesterone device; T-shaped, 32mm x 32mm, insertion tube diameter 4.4mm, sits in the uterus with threads through the cervix; main action thickens cervical mucus, also thins the endometrium, sometimes stops ovulation; benefit: lightens or stops periods; risks mainly relate to insertion (perforation, infection, expulsion).
  • Copper IUD: failure rate 0.8%; lasts 5 or 10 years; no hormones; acts via a foreign body reaction, alters mucus and endometrium, impedes sperm, prevents implantation; side effect: heavier, more painful periods; insertion risks similar to the Mirena IUS.

Tier 2: Injectable and Oral Contraceptives

  • Depo-Provera injection: typical failure rate 3%; 150 mg/mL medroxyprogesterone, given IM every 13 weeks, effect lasts up to 14 weeks; high-dose progesterone; stops ovulation; risks: irregular or no bleeding, reversible loss of bone density, delayed return to fertility, weight gain.
  • Progesterone-only pill (POP): failure rate 6-8%; low-dose progesterone tablet taken daily, cannot miss pills; examples: Noriday and Microlut (3-hour window), Cerazette (12-hour window); thickens cervical mucus, sometimes stops ovulation; benefit: safe for most people.
  • Combined oral contraceptive (COC): failure rate 6-8%; oestrogen + progesterone (e.g. Oralcon, Norimin); 21 days hormone pills then 7 days placebo, or continuous taking by skipping the placebo pills; main action stops ovulation, also thickens mucus and thins the endometrium; benefit: allows control of bleeding; risk: oestrogen carries many contraindications from increased VTE, clotting risk and oestrogen-dependent conditions.
  • COC absolute (MEC 4) contraindications: migraine with aura; postpartum <6 weeks if breastfeeding or <3 weeks if not breastfeeding; age >35 and smoking >15/day; pregnancy; uncontrolled hypertension; vascular disease; ischaemic heart disease; stroke; TIA; VTE; increased clotting risk; current breast cancer; severe liver problems. MEC 3 covers many additional relative contraindications.

Tier 3: Barrier, Withdrawal and Fertility Awareness Methods

  • Typical failure rate >10%.
  • Includes male and female condoms, the withdrawal method, and the rhythm (fertility awareness) method.

Emergency Contraception

  • Copper IUD: the most effective emergency contraceptive; failure rate <1%; prevents implantation, so must be inserted before implantation occurs. The egg is viable for about 1 day after ovulation and sperm survive up to 5 days in the tract, giving a fertile window of roughly 5-7 days before to 1-2 days after ovulation. Insert if within 5 days of the earliest expected ovulation, or within 5 days (120 hours) of a single episode of unprotected sex. The fertilised egg travels the oviduct/uterus for 5-6 days, and implantation occurs 6-7 days after fertilisation, after which the device must not be inserted.
  • Levonorgestrel ECP (1.5mg): failure rate approximately 5%; a higher-dose progestin than in POP/COC; licensed for use <72 hours after unprotected sex, most effective if <12 hours after; delays ovulation when taken before the LH surge by mimicking negative feedback and suppressing FSH/LH secretion, preventing the LH surge.

Permanent Contraception

  • Vasectomy: failure rate 0.15%; performed under local anaesthetic by separating the vas deferens (several surgical methods exist); prevents semen release; requires an 8-12 week clearance check; complications: infection, haematoma, post-vasectomy pain syndrome; reversal may not be successful.
  • Tubal ligation: failure rate 0.5%; less effective and higher risk than the Mirena IUS; prevents fertilisation by blocking or cutting both fallopian tubes (cauterised, tied and cut, or banded/clipped); day case procedure; reversal may not be successful.

Gillick Competency and Fraser Guidelines

  • The Fraser guidelines set criteria that must be met to judge a young person Gillick competent to receive contraceptive advice/treatment. Mnemonic: “UnProtected SSexual InterCourse”:
    • Understands the doctor’s advice.
    • Can’t be Persuaded to inform the parents.
    • Likely to begin or continue having Sexual intercourse.
    • Mental or physical health likely to Suffer unless provided contraception.
    • In their best Interests to provide contraceptive advice/treatment.
    • Confidentiality is maintained.

The Consultation and Scenario

  • Consultation checklist: factors influencing the individual’s choice (e.g. periods, efficacy); PMHx (including smoking, migraines), medications, allergies, FHx (including VTE) for medical safety; age and competency for legal obligations/safety; social situation and IPV screening for patient safety; BMI, BP, STI risk (swabs), pregnancy risk (pregnancy test) — then offer options with safety/efficacy information and leave the choice to the patient.
  • Wider factors shaping choice: bleeding impact, efficacy, medical conditions, additional benefits, personal perceptions/concerns, ethical and spiritual beliefs, pregnancy desires and goals, influence of others, access including cost, and age/reproductive stage.
  • Worked scenario: a 15-year-old sexually active female wants to start contraception. Periods a bit painful but not heavy; doesn’t want pregnancy soon; planning further study. No relevant PMHx, non-smoker, no migraines, no medications or allergies; mother had an unprovoked DVT at age 30. She meets the Fraser criteria (understands advice, parents aware, likely to continue, would suffer otherwise, best interests served, confidentiality maintained). Safe/happy at home, school and in her relationship; boyfriend also 15, both were virgins beforehand. BMI 20, BP 110/60, no STI risk, pregnancy test negative, using condoms reliably.
  • Options discussed: LNG-IUS (Mirena) - LARC, 0.2% failure, reduces period pain, has procedure/risks; Depo/DMPA - 3% failure, injection every 13 weeks, weight gain, reduced bone density, delayed return to fertility; Jadelle implant - LARC, 0.1% failure, variable bleeding pattern, procedure/risks; POP - 6-8% failure, must be taken daily within a 3 or 12 hour window, variable bleeding pattern.
  • Not recommended: copper IUD (likely to worsen her period pain); COC/CHC (MEC 3, since a first-degree relative with VTE under age 45 makes CHC UKMEC category 3 for VTE risk, while Cu-IUD, LNG-IUS, implant, DMPA and POP all remain UKMEC category 1 for the same family history) — safer options should be tried first. Final decision remains the patient’s choice.

Self-test

  1. Describe the hormonal chain of command that drives the menstrual cycle, from the hypothalamus to the endometrium.
  2. List the ovarian follicle stages in order from primordial follicle to corpus albicans.
  3. Describe the actions of oestrogen and progesterone on the endometrium during the proliferative and secretory phases respectively.
  4. Explain how oestrogen and progesterone feedback to the hypothalamus and pituitary changes across the cycle, and when it becomes positive rather than negative.
  5. Describe the mechanism by which combined hormonal contraceptives and high-dose progesterone-only methods suppress ovulation.
  6. Describe the mechanism by which low-dose progesterone-only methods act, and how this differs from the ovulation-suppression mechanism above.
  7. Distinguish “perfect use” from “typical use” failure rates, and give an example method where the two differ markedly.
  8. List the methods in Tier 1, Tier 2 and Tier 3, with one distinguishing feature of each tier.
  9. What do MEC categories 1-4 mean?
  10. Describe the failure rate, duration and mechanism of action of the Jadelle implant.
  11. Distinguish the hormonal IUS (Mirena/Jaydess) from the copper IUD in terms of mechanism, duration and side effects.
  12. List the absolute (MEC 4) contraindications to the combined oral contraceptive pill.
  13. A patient has a first-degree relative with a VTE before age 45. According to the UKMEC summary table, which methods remain category 1 and which becomes category 3?
  14. Describe the timing rules for using the copper IUD as emergency contraception, based on the biology of fertilisation and implantation.
  15. Describe how the levonorgestrel emergency contraceptive pill works, and state its licensed and most-effective time windows.
  16. Distinguish vasectomy from tubal ligation in terms of mechanism of action and failure rate.
  17. State the Fraser guidelines criteria for Gillick competence, using the mnemonic given in the lecture.
  18. Predict what happens to the cycle if a contraceptive only thickens cervical mucus (as with low-dose progesterone methods), compared with one that fully suppresses the LH surge (as with combined or high-dose progesterone methods).

Answers

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