Table 1.

Emergency contraceptive methods and their action, failure rate, the window of efficacy, and advantages

Emergency contraceptive method and dose	Mechanism of action	Failure rate (occurrence of pregnancy after the use of EC)	The window of efficacy after an unprotected sexual encounter (UPSE)	Advantages over other ECs
Copper IUD	• The toxic effect on sperm and ova • Harmfully affect motility and viability of sperm • Adversely affect viability and transportation of ova • It prevents implementation by a local endometrial inflammatory reaction	< 1%	It can be inserted within 5 days after the UPSE in a cycle or within 5 days of the earliest estimated date of ovulation, whichever is later	• Copper IUD is the only method that is effective after the starting of ovulation • Copper IUD is not affected by BMI of the individual or action of any drugs
ECPs containing ulipristal acetate (30 mg single oral dose)	• Delays ovulation for at least 5 days until sperm from the UPSE is no longer viable (It delays ovulation even after the start of the luteinising hormone (LH) surge)	1.3–2.1% Fine et al. [52]	Within 3–5 days after UPSE Glasier et al. [53]	• UPA–ECP is the only oral EC that is expected to be effective if UPSE took place 96–120 h ago (LNG-ECP is ineffective if taken more than 96 h after UPSE)
ECPs containing Levonorgestrel (LNG) (1.5 mg single oral dose or 3 mg when the woman is taking the enzyme-inducing drug or has a BMI of more than 26 kg/m2)	• If taken before the start of the LH surge, it delays or prevents follicular rupture and causes luteal dysfunction • Delays ovulation for at least 5 days until sperm from the UPSE is no longer viable	0.6–2.6%	Within 72 h after UPSE	• LNG-ECP is effective even if a woman has recently taken progestogen (The effectiveness of UPA-EC could theoretically be reduced in this case)