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 Introduction
Postcoital contraception (PCC) or
emergency contraception (EC) is a method
of birth control used after unprotected
sexual intercourse and before
implantation. Unwanted pregnancy is
common with about 50 million pregnancies
terminated every year worldwide(1).
EC typically refers to the
administration of drugs within 72 hours
to women who have had unprotected sexual
intercourse or to those who have had a
failure of another method of
contraception e.g. broken condom or a
perceived failure of coitus interruptus.
As implantation does not occur till
around seven days after ovulation the
use of emergency contraception is not
considered equivalent to therapeutic
abortion.
The apparent efficacy of the EC can be
attributed to the limited time during a
cycle when pregnancy is possible in the
human female(2). The possibility of
pregnancy is estimated from an analysis
by Dixon (1980) (3).
Causes of failure of emergency
contraception in clinical practice (4).
Include :
1. Poor compliance
2.Vomitting within 3 hours of ingestion
3. Non-use of contraception for the rest
of the cycle
4. An inaccurate menstrual or coital
history
The
main types of EC are ;
Oestrogen Progestogen (Yuzpe) method
Introduced in 1977 it has been the main
method of hormonal postcoital
contraception (PCC) in the form of
Schering PC4. Each tablet contains 50ug
ethinyloestradiol and 250ug
levonorgestrel (5). This should be taken
within 72hrs of unprotected sexual
intercourse. The efficacy is measured
using the pregnancy rate in comparison
to expected pregnancies as measured by a
table formulated by Dixon 1980(3). If we
consider only those who would have got
pregnant, the opinion of Professor
Trussell of Princeton (1990) is that the
Yuzpe method prevents 75% of conceptions
(1,9).
Recent studies have shown that efficacy
is highly dependent on the lapse of time
between the unprotected sexual
intercourse (UPSI) and use of the Yuzpe
method(6,8,9,10). At less than 24 hr
interval the pregnancy rate is 2% rising
to 4.7% at 49hrs and over (10).
Emergency
intrauterine device
Intrauterine devices, particularly those
containing copper compromise
fertilization by the toxic effect of
Copper on the sperm or (theoretically)
by preventing implantation(1).
Used up to five days after UPSI or 5
days after the calculated ovulation
date. It has a very high efficacy with a
failure rate of less than 1% with only
four failures reported (Smith 1994). It
can be also used as a long term method
of contraception once inserted covering
multiple occasions of UPSI occurring
within five days (11). and for as long
afterwards as the device remains in
place. Some couples prefer to remove the
device after the next period and use
other contraceptive choices. However
most of the risks associated with an
IUCD insertion occur within the first
few weeks of insertion.
Progestogen
only (Po)
This method has long been used as the HO
& Kwan method for women with
contraindications to the combined EC.
However, it has now gained sudden
momentum since the WHO study published
late in the 1990's.
Two doses of 0.75mg levonorgestrel taken
12 hours apart and started up to 72hrs
after UPSI.
A double blind randomized controlled
trial involving 2000 women run by the
WHO provided proof that the progestogen
only emergency contraceptive is more
efficient than the Combined EC having a
pregnancy rate of 1.1% compared to a
3.2% for the combined EC. It was also
noted that the earlier the EC was used
the more efficient it is in both
types(6). Delaying the first dose by 12
hours increased the odds of pregnancy by
almost 50% (8).
Preplanned
use of hormonal emergency contraception
High
dose levonorgestrel 0.75mg single dose
taken within one hour of intercourse up
to 4 times per cycle. Work in Hungary
showed it to have a failure rate of
1-3%(5).
High-dose
ethinyloestradiol or equine oestrogens
Within 72 hours of exposure and for 5
days . The main effects are prolonged
common nausea and vomiting but appears
to have a failure rate of 0.7-1.6% (5).
Danazol
Taken in two doses 12 hrs apart is of
uncertain efficacy(5).
Mifipristone
Is an antiprogestational agent that
theoretically interferes with
implantation. A single dose of 600mg
seems to be as efficient as the PC4 and
has less side effects except for a delay
in menses . Research into its use is
severely restricted by its efficacy as
an abortifacient agent(1,5,12).
Administration
of Hormonal Emergency Contraception
Despite the linear relationship between
the efficacy and time interval between
intercourse and treatment 10 researchers
have recently began questioning the 72
hr limit on the use of the Yuzpe
regimen. Ellertson, et. al, who recently
studied the failure rate in women using
the Yuzpe method believe the 72 hrs to
be needlessly restrictive. The failure
rate they quote is 1.9% and 3.6% in
perfect and typical use consecutively
between 72 and 120 hours. This is in
comparison to 2.0% and 2.5% during
typical use prior to 72hrs(13).
The fact that we need two doses of
emergency contraception is being
challenged. It appears that Albert
Yuzpe's choice of two doses 12 hours
apart was arbitrary(14 ) (personal
communication, A.Yuzpe, August 10,
2000). He had also used high doses of
Ovral from Wyeth a combined pill which
he was working on at the time . This
brings to mind whether any other
combined contraceptive would do. The
ideal emergency contraceptive would be
easily available to women and the less
the number of doses the better.
A multicentre randomized controlled
trial recently published has come up
with some answers. They found clear
evidence that a regimen using
northisterone instead of levonorgestrel
in combination with ethinyloestradiol is
safe and effective as emergency
contraception. They also noted that
women who used only a single dose of
combined emergency contraception
experienced half the vomiting but showed
no statistically significant difference
in efficacy(15).
A WHO multicentre study found that
taking both doses of the standard
levonorgestrel regimen at the same time
is as effective as taking the two doses
12 hrs apart(16).
The
future
New developments in emergency
contraception give hope for a more
effective, available method with minimal
side effects. This would hopefully lead
to an increase in the use of the method
and a reduction of unwanted pregnancies.
It is source of great sorrow that large
portions of the world currently have no
access to emergency contraception
services even when pregnancy can be a
disaster and where therapeutic abortion
is not legal.
Efficacy
of postcoital contraception Summary
In the last few years contraception
services have been fine tuning the
provision of hormonal contraception.
An easily available medication with
minimal side effects, high efficacy and
few contraindications, is the future for
emergency contraception.
This review goes through the old, new
and future of emergency contraception.
The more light is thrown on emergency
contraception worldwide the less
unwanted pregnancies and abortions.
References
Other
Topics:
Review Article # 1
- Oligoanalgesia: The
Challenge in the Emergency Department
Review Article # 2
- Ectopic Pregnancy - An update
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