Obstetrics and gynaecology · Hard
This case is fictional and exists for study. It describes no real patient.
26 years · female
A 26-year-old female presents to the clinic requesting emergency contraception after an episode of unprotected sexual intercourse 48 hours ago. She has regular 28-day menstrual cycles, and her last menstrual period started 12 days ago. Her medical history is significant for focal epilepsy, well-controlled on carbamazepine. She takes no other medications and has no drug allergies. She has never been pregnant and wishes to discuss both emergency options and long-term maintenance contraception that will not interact with her anti-seizure therapy. Physical examination is unremarkable, and a point-of-care urine pregnancy test is negative.
Vital signs
- HR
- 72 bpm
- BP
- 120/78 mmHg
- RR
- 14/min
- Temp
- 36.7 °C
- SpO₂
- 99%
Examination findings
- Abdomen soft, non-tender, no organomegaly
- Bimanual pelvic examination normal with no cervical motion tenderness
Investigations
| Urine beta-hCG | Negative qualitative | reference: Negative |
Question 1 of 3
Which of the following is the most appropriate first-line emergency contraceptive option for this patient?
The copper intrauterine device (Cu-IUD) is the most effective form of emergency contraception (>99% effective) and is the first-line recommendation for all women presenting within 120 hours of unprotected sexual intercourse, regardless of liver enzyme-inducing drug use. Carbamazepine is a strong hepatic enzyme inducer that increases the metabolism of oral hormonal emergency contraceptives. While double-dose levonorgestrel (3.0 mg) can be offered if a Cu-IUD is declined or contraindicated, the Cu-IUD remains the single most effective first-line action. Ulipristal acetate is ineffective and not recommended in women taking enzyme inducers.
Teaching point: The Cu-IUD is the most effective emergency contraceptive method and is unaffected by enzyme-inducing drugs.
Question 2 of 3
The patient declines any intrauterine device and requests a non-intrauterine long-term contraceptive method. Which of the following is the most appropriate choice considering her anti-seizure medication?
Carbamazepine induces cytochrome P450 enzymes, which increases the clearance of systemic oestrogens and progestogens. This reduces the efficacy of combined hormonal contraception and of progestogen-only pills, both of which are UKMEC 3 with enzyme-inducing drugs. The etonogestrel subdermal implant is UKMEC 2, not 3 — the interaction is not harmful, but plasma etonogestrel falls and contraceptive efficacy cannot be relied upon, so the FSRH advises a method unaffected by enzyme inducers in preference; if the implant is used, condoms must be used consistently in addition. Depot medroxyprogesterone acetate (DMPA) injection is UKMEC 1 because the serum progestogen levels achieved after deep intramuscular injection are sufficiently high to maintain contraceptive efficacy despite enzyme induction.
Teaching point: Depot medroxyprogesterone acetate (DMPA) injection is unaffected by liver enzyme-inducing drugs and is UKMEC 1.
Question 3 of 3
During counselling, the patient mentions that her sister was refused combined hormonal contraception due to a history of migraine with aura. What is the UK Medical Eligibility Criteria (UKMEC) classification and primary rationale for withholding combined hormonal contraceptives in patients with migraine with aura?
Migraine with aura at any age is classified as UKMEC 4 ('unacceptable health risk') for combined hormonal contraception. Ethinylestradiol increases the risk of arterial thrombosis; combined with focal neurological symptoms (aura), this synergistically multiplies the baseline risk of ischaemic stroke. While combined pills do increase venous thromboembolism risk, the specific rationale for the UKMEC 4 rating in migraine with aura is ischaemic stroke.
Teaching point: Migraine with aura is a UKMEC 4 absolute contraindication for combined hormonal contraception due to elevated ischaemic stroke risk.
Key learning points
- Cu-IUD is the most effective emergency contraceptive and is unaffected by enzyme-inducing medications.
- Depot medroxyprogesterone acetate (DMPA) injection and IUDs (Cu-IUD/LNG-IUS) are UKMEC 1 choices in patients taking hepatic enzyme-inducing drugs.
- Migraine with aura is classified as UKMEC 4 for all combined hormonal contraceptives due to a significantly increased risk of ischaemic stroke.
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