Family doctor


Sexual Health



This article outlines the methods used to prevent pregnancy after unprotected sexual intercourse.

Emergency contraception - a patient’s guide


‘Emergency contraception’ is the term used to describe methods employed in trying to prevent pregnancy following unprotected sexual intercourse (UPSI) or potential contraceptive failure. It has been called ‘postcoital contraception’ or ‘the morning-after pill’ in the past but these terms are less used nowadays.


Emergency contraception may be required in a range of different situations, such as following:

  • Consensual sex where no contraception was used
  • A mistake with oral contraception
  • Rape or sexual assault; when using the withdrawal method
  • Ejaculation onto the external genitalia
  • A burst, dislodged or incorrectly used condom
  • A diaphragm is incorrectly inserted, damaged, dislodged or removed within 6 hours of sex


Usually if a woman has had to use emergency contraception it is a good idea to then discuss with your doctor about initiating or adapting a method of reliable contraception


Hormonal and non-hormonal methods


Currently in New Zealand, women can be offered an oral hormonal method (levonorgestrel 1.5mg known as Postinor-1 taken as a single dose) or a copper-bearing intrauterine device (IUD).


Previously Postinor-2 (levonorgestrel 750ug) was available which contained half the dose of Postinor-1 but there were two tablets taken 12 hours apart (so the total daily dose was the same as Postinor-1). However studies showed that when the dose was taken all at once (as in Postinor-1) that it was more effective at preventing pregnancy. The Yuzpe regimen (a combined oestrogen–progestogen regimen) was also previously used in the New Zealand but this tended to have high rates of nausea and vomiting associated with it, and is no longer recommended.


Postinor-1 is now available over-the-counter: this means it can be purchased from a pharmacy.


Timing is important


There is no time in the menstrual cycle when there is no risk of pregnancy following UPSI - this is because the timing of fertility can be highly unpredictable which is especially true if the cycle is irregular or if there is uncertainty about the date of the last menstrual period. Nevertheless, the probability of pregnancy in the first 3 days of the cycle is considered negligible.


If consulting with a doctor about emergency contraception, the information that the doctor will want is:

  • The most likely date of ovulation (this is calculated on the date of the last menstrual period and the usual cycle length)
  • When the first episode of UPSI occurred in the current menstrual cycle
  • Details of the contraceptive failure(s)

Using Postinor-1


Postinor is licenced for use within 72 hours of UPSI. When used within 72 hours, Postinor -1 prevents 84% of expected pregnancies. It is recommended that Postinor-1 is taken as soon as possible after UPSI, preferably within 12 hours. UPSI within 12 hours of a dose of Postinor does not require further treatment with a repeat dose of Postinor-1.


After taking Postinor-1 it is recommended that a barrier method of contraception (i.e. condoms, diaphragms) is used until the next menstrual period begins, however some doctors may choose to start a regular contraceptive pill immediately so as not to risk another episode of UPSI. If a woman is already on the oral contraceptive she may continue to take it as usual. After taking Postinor-1, the timing of the next menstrual period can disturbed but will normally be within 7 days of the expected time. If it is more than 7 days overdue then pregnancy should be ruled out with a pregnancy test.

It is reasonable to do a follow up pregnancy test for peace of mind in any event.


How does Postinor-1 work?


The mode of action of Postinor-1 is incompletely understood, however, it is thought to be effective mainly due to inhibition of ovulation rather than inhibition of implantation. If taken prior to ovulation, Postinor-1 can inhibit ovulation for 5–7 days, by which time any sperm in the upper reproductive tract have lost their fertilising ability.


Contraindications to Postinor-1 (i.e. reasons NOT to take it):

  • Pregnancy (or possibility of pregnancy such the expected menstrual period is late, or the last period was unusual)
  • Since the last period there has been unprotected sex more than 72 hours ago (in which case a pregnancy may have already occurred)


Medical situations where Postinor-1 is not recommended


  • Severe liver problems
  • Malabsorption problems (such as Crohns disease) and may not absorb it properly
  • Severe hypertension, ischaemic heart diseae, stroke
  • Diabetic complications (such as kidney, eye or nerve damage)
  • Breast cancer

Reasons to need 2 x Postinor-1 (i.e. levonorgestrel 3mg)


The metabolism of Postinor-1 is speeded up by simultaneous use of certain medicines sometimes referred to as ‘liver enzyme inducers’. The common medicines that are in this group are:

  • Phenytoin, carbamazepine, primidone, barbiturates
  • St John’s Wort
  • Rifampicin
  • Griseofulvum


Women who take these medicines and require emergency contraception and choose to use Postinor-1 will need to be given 2x 1500mg to take as a single dose within 72 hours of UPSI. The IUD is seen as the preferred option for women taking liver enzyme inducers.


Copper-IUDs – how do they work at preventing pregnancy?


It has been shown that IUDs have both pre-and post-fertilisation effects which contribute to their  effectiveness. Firstly they causes changes in the copper content of cervical mucus which may inhibit sperm penetration and, in addition, they cause an inflammatory reaction within the lining of the uterus may have an anti-implantation effect should fertilisation occur. 


IUD insertion for emergency contraception is recommended for up to 5 days post UPSI. This means that if a woman is too late for Postinor-1 (i.e. UPSI was >72 hours ago) she might be able to have an emergency IUD inserted if UPSI took place less than 5 days previously.


An emergency IUD can be removed after the next menstrual period without risk of pregnancy, provided no UPSI has occurred since menstruation or if hormonal contraception is started within the first 5 days of the cycle. Some women may choose to not get the IUD removed at the next menstrual period but continue with it for long term contraception.


The doctor who inserts the emergency IUD will usually prescribe antibiotics to eliminate the risk of possible infection spreading into the pelvis from any potential sexually transmitted infection.


Not all GPs are trained or experienced in the insertion of IUDs – it is best to check first before assuming that they will be able or prepared to insert one if it is needed. Family planning clinics are often a good alternative.




Faculty of Sexual and Reproductive Healthcare
FFPRHC Guidance (April 2006). Emergency contraception


Medsafe data sheet Postinor-1



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