Introduction
Unprotected intercourse after oral emergency contraception (EC) significantly increases pregnancy risk. This underlies the importance of promptly starting effective, ongoing contraception – known as ‘quick starting.’ However, theoretical concern exists that quick starting might interact with EC or hormonal contraception (HC) potentially causing adverse side effects.

Method
A systematic review was conducted, evaluating quick starting HC after oral EC (levonorgestrel 1.5mg [LNG] or ulipristal acetate 30mg [UPA]). PubMed, EMBASE, The Cochrane Library, ICTRP, ClinicalTrials.gov and relevant reference lists were searched in February 2016. A lack of comparable studies prevented meta-analysis.

Results
Three randomised controlled trials were identified. Two biomedical studies suggested HC action was unaffected by quick starting after UPA; one study examined ovarian quiescence (OR: 1.27; 95% CI 0.51 to 3.18) whilst taking combined oral contraception (COC). Another assessed cervical mucus impenetrability (OR: 0.76; 95% CI 0.27 to 2.13) whilst taking progestogen-only pills (POP). Quick starting POP reduced the ability of UPA to delay ovulation (OR: 0.04; 95% CI 0.01 to 0.37). Side effects (OR: 1.22; 95% CI 0.48 to 3.12) and unscheduled bleeding (OR: 0.53; 95% CI 0.16 to 1.81) were unaffected by quick starting COC after UPA. Another study reported higher self-reported contraceptive use at eight weeks amongst women quick starting POP after LNG, compared to women given LNG alone (OR: 6.73; 95% CI 2.14 to 21.20).

Conclusion
Limited evidence suggests quick starting HC after UPA does not reduce HC efficacy, however it reduces UPA efficacy. Consequently, women should delay starting HC after UPA.

Quick starting hormonal contraception after using emergency contraception: a systematic review

The Joint Annual Conference of the British Association for Sexual Health and HIV & the Society for the Study of Sexually Transmitted Diseases in Ireland