Emergency contraception (EC) is defined as any drug or device used after intercourse to prevent pregnancy. One marketed hormonal method (levonelle-2, LNG 1.5 mg taken as a single dose within 72 h of intercourse) is available in the UK. The Yuzpe regimen, a combination of 100 p,g ethinyloestradiol and 0.5 mg LNG taken twice with the two doses separated by 12 h is no longer marketed, but the same hormones are available in some brands of COC if levonelle-2 is unavailable.
Levonorgestrel 1.5 mg (LNG-EC) inhibits or delays ovulation if it is taken in the early to mid-follicular phase of the cycle. The risk of pregnancy at this time is less than 20%. Within 48 h of ovulation, when the risk of pregnancy is around 30%, LNG-EC appears to be ineffective in inhibiting ovulation. If ovulation does occur abnormalities of the luteal phase are common but the effect of these on fertility is unclear. There is no evidence that LNG-ED interferes with implantation.
There has never been a placebo-controlled trial of EC effectiveness and accurate estimates of efficacy are difficult to make. Many women are unsure of the exact date of their last menstrual period and most do not ovulate on exactly the same day each cycle. The majority of women who use emergency contraception are of unproven fertility and many use it after an accident with a condom which may not in fact have resulted in the leakage of seminal fluid. The chance of conception following one act of intercourse has been calculated to be around 27% per cycle so that even without emergency contraception over 70% of women will not conceive. While it has been suggested that LNG-EC may prevent as many as 90% of pregnancies, particularly if it is used soon after intercourse, this figure is probably a huge overestimate. Beyond 72 h after intercourse, given the likely mechanism of action, LNG-EC is even less effective.
LNG-EC is free from side effects. Subsequent menses normally occur at the expected time. Few data are available on the safety of LNG-EC but the World Health Organization advises that there are no contraindications to its use .There is no evidence that the regime is teratogenic should it fail to prevent pregnancy.
The copper IUD (but not the LNG-IUS) is a highly effective emergency contraceptive with failure rates of less than 1%. In the UK it is used for up to 5 days after the estimated day of ovulation, which may be more than 5 days after intercourse. It is particularly appropriate for women who wish to continue the IUD as a long-term method of contraception. Most women requesting emergency contraception are however young and nulli-parous and it can sometimes be difficult to insert a device. Simultaneous antibiotic treatment for chlamydia infection is recommended for women at risk.
In 2003 6% of women of reproductive age had used emergency contraception at least once in the past year. Among women aged 16-17 that figure rose to 20%. A number of studies suggest that around 11% of women presenting for abortion in the UK used emergency contraception to try to prevent the pregnancy. More than seven studies, undertaken in a variety of countries and settings, and using a variety of methods of emergency contraception, have shown that advanced provision of EC (giving a supply to be kept until needed) increases use. It also encourages earlier use and, except in adolescents, does not lead to the abandonment of more reliable methods of contraception. Increased use of EC, however, has not as yet been shown to reduce abortion rates.
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The first trimester is very important for the mother and the baby. For most women it is common to find out about their pregnancy after they have missed their menstrual cycle. Since, not all women note their menstrual cycle and dates of intercourse, it may cause slight confusion about the exact date of conception. That is why most women find out that they are pregnant only after one month of pregnancy.