What is the initial workup for initiating combined oral contraceptive therapy in a woman?

Initial Workup for Combined Oral Contraceptives

The initial workup for starting combined oral contraceptives requires only a blood pressure measurement—no pelvic examination, laboratory tests, or additional screening is necessary before initiation. 1

Required Examination

• Blood pressure measurement is the only examination needed before initiating combined hormonal contraceptives (CHCs), which includes combined oral contraceptive pills 1
• No bimanual examination, cervical inspection, or laboratory testing is required 1
• Weight and BMI measurement are not required to determine medical eligibility, though baseline weight may be helpful for future discussions about weight changes 1

Clinical History Assessment

While formal examinations are minimal, you should assess for contraindications through history:

Absolute Contraindications (Category 4)

• Smoking ≥15 cigarettes/day in women ≥35 years old (unacceptable cardiovascular risk) 2
• Current or history of venous thromboembolism 2, 3
• Known thrombogenic mutations 3
• Current breast cancer 2
• Migraine with aura (stroke risk) 2, 4
• Severe hypertension 2
• Complicated valvular heart disease 2

Relative Contraindications (Category 3)

• Smoking <15 cigarettes/day in women ≥35 years old (use only if other methods unavailable) 2
• Adequately controlled hypertension 2
• Migraine without aura in women ≥35 years 2

Drug Interaction Screening

Assess current medications for interactions:

• Enzyme-inducing anticonvulsants (phenytoin, carbamazepine, barbiturates, primidone, topiramate, oxcarbazepine) reduce COC efficacy 1
• Rifampin or rifabutin significantly reduce contraceptive effectiveness and require alternative methods 1, 5
• Lamotrigine levels may be reduced by COCs, requiring monitoring 1
• Most common antibiotics do NOT reduce COC efficacy 1, 5
• HIV medications have varying interactions depending on the specific agent 1

Timing of Initiation

• COCs can be started anytime if you are reasonably certain the patient is not pregnant 1
• If started ≤5 days after menses began, no backup contraception is needed 1
• If started >5 days after menses, use barrier methods or abstinence for 7 days 1
• Quick Start approach (starting on the day of visit) is acceptable even with uncertainty about pregnancy, with follow-up pregnancy test in 2-4 weeks 1, 6

Common Pitfalls to Avoid

• Do not delay initiation waiting for menses—this increases unintended pregnancy risk 6
• Do not require pelvic examination before prescribing COCs—this creates unnecessary barriers to access 1
• Do not order routine laboratory tests (lipids, glucose, liver function) unless clinically indicated by history 1
• Do not assume all antibiotics reduce efficacy—only rifampin/rifabutin are clinically significant 1, 5
• Do not prescribe COCs for migraine with aura—this is an absolute contraindication due to stroke risk 2, 4

Formulation Selection

• First-line formulations contain levonorgestrel or norethindrone with ≤35 mcg ethinylestradiol, which have the lowest VTE risk among combined pills 7
• Newer progestins (desogestrel, gestodene, drospirenone) carry higher VTE risk compared to levonorgestrel 3, 7
• Natural estrogens (estradiol, estetrol) may have more favorable metabolic profiles but are not necessarily first-line 8, 4