🔑 Key Learning

  • LARCs are the most effective forms of contraception as they are not user-dependent.
  • NICE advises offering the method preferred by the woman, unless contraindicated.
  • Combined hormonal contraception (CHC) has more contraindications than progestogen-only methods or LARCs.
  • Enzyme inducers reduce the efficacy of hormonal contraceptives—recommend CU-IUD, LNG-IUS, or injectable instead.
  • Missed pill rules differ for POP vs CHC and should be followed carefully to reduce pregnancy risk.

🧬 Methods of Contraception

  • Barrier: Condoms
  • Combined hormonal contraception (CHC): COCP, transdermal patch
  • Progestogen-only: POP, implant, injectable
  • LARCs (not user-dependent):
    • Intrauterine: Levonorgestrel IUS (e.g. Mirena), Copper IUD
    • Progestogen-only implant (e.g. Nexplanon)

💥 Adverse Effects

Levonorgestrel IUS (LNG-IUS)

  • Risk of expulsion: 1 in 20
  • Hormonal: acne, breast tenderness, mood changes
  • Cramping, irregular bleeding or amenorrhoea

Copper IUD (Cu-IUD)

  • Expulsion: 1 in 20
  • Pelvic pain, dysmenorrhoea
  • Heavier periods, intermenstrual bleeding

Progestogen-only Implant

  • Unscheduled, irregular, sometimes heavy bleeding
  • Reduced efficacy with enzyme inducers

â›” Contraindications

A full list of UKMEC 4 (contraindicated) and UKMEC 3 (risks>benefits) can be viewed  at the following: https://www.fsrh.org/standards-and-guidance/documents/ukmec-2016/

CHC - UKMEC 4 (Examples)

  • Breastfeeding <6 weeks postpartum
  • < 3 weeks postpartum with RFs for VTE
  • Uncontrolled HTN >160/100
  • History of VTE/stroke/IHD
  • Migraine with aura
  • Smoking >15/day if >35 yrs
  • BRCA1/2 or active breast cancer

IUD/IUS

  • Unexplained PV bleeding
  • Active pelvic infection or STI
  • Postpartum sepsis

Other

  • Unexplained PV bleeding: UKMEC 4 for IUD/IUS; UKMEC 3 for POP/injectable
  • Teratogenic drugs (e.g. valproate): use highly effective contraception (preferably 2 methods, including LARC)

💊 Drug Interactions

Enzyme Inducers (PC BRAS)

Inducers can interact with, and reduce the efficacy of hormonal contraception. Offer LARCs which are unaffected (CU-IUD, LNG-IUS, Depo injection). 

  • Phenytoin
  • Carbamazepine
  • Barbiturates
  • Rifampicin
  • Alcohol (chronic)
  • Sulphonylureas
  • St John's Wort
  • Reduce efficacy of CHC, POP, implant — use IUD/IUS or injectable

Lamotrigine

  • Not an inducer but interacts with CHC (lowers lamotrigine levels → seizure risk)
  • CHC contraindicated
  • POP may raise lamotrigine levels → increased SEs

🧪 Missed Pill Rules

Progestogen-Only Pill (POP)

  • Missed if >3 hrs late (12 hrs for desogestrel, 24 hrs for drospirenone)
  • Advice:
    • Take missed pill ASAP
    • Use barrier for 48 hrs
    • Emergency contraception if sex since missed dose or within 48 hrs of restarting

Combined Oral Contraceptive Pill (COCP)

  • Missed = >24 hrs late
  • 1 missed pill: take it ASAP, no precautions needed
  • 2+ missed:
    • Take one ASAP
    • Barrier precautions for 7 days
    • If missed from 1st 7 pills → emergency contraception
    • If from last 7 pills → skip pill-free week

Vomiting & Diarrhoea

  • Vomit within 3 hrs → take another
  • If D&V >24 hrs → follow missed pill rules
  • Use barrier method during illness + 7 days after

🔗 Useful Links and References