 Introduction
The
search for an ideal contraceptive which does not interfere with spontaneity or
pleasure of the sexual act, yet effectively controls the fertility, is still continuing.
Numerous contraceptive techniques are available, yet contraceptive coverage continues
to be poor in India as most people are either ignorant or shy, or do not want
to use a contraceptive continuously regardless of sexual activity for fear of
side-effects (pill or intra-uterine device), or do not like to use methods linked
with coitus (barriers like condom or diaphragm). Thus even when not planning for
a pregnancy, exposure to unprotected sex takes place often, necessitating the
use of Emergency Contraception, to avoid the potential hazards of pregnancy termination.
This need may also arise due to failure of contraceptive method being used (condom
rupture, diaphragm slippage, forgotten oral pills) or following sexual assault.
The risk of pregnancy following a single act of coitus varies from 4-25% depending
on the time when intercourse takes place during the menstrual cycle. Risk is more
when sexual exposure occurs close to ovulation. Emergency contraception
is really not a new concept . In the literature written 2000 years ago, we find
evidence of various herbs to be used for the ‘morning after’. A number of ineffective
folklore methods which are rather unscientific, like use of vaginal douching using
different agents, blowing nose or jumping backwards have been used to prevent
conception following unprotected coitus. Mechanism
of action Several
opportunities are offered during the reproductive process to interrupt the process
of conception, rather than resorting to abortion. But, usually when couples fail
to take precautions, they only keep hoping and praying that pregnancy would not
take place and wait anxiously for luck and nature to decide their fate.
Emergency contraceptives act as interceptive agents i.e. ovulation, fertilization
or implantation is prevented depending on the phase of menstrual cycle.
If used before ovulation, follicular maturation as well as ovulation is disrupted.
Following ovulation implantation of blastocyst is interfered with by causing asynchronous
endometrial maturation. Function of corpus luteum is also affected and progesterone
surge does not take place. There is a fall in the level of endometrial carbonic
anhydrase which is important for stickiness of blastocyst. Progesterone also acts
by increasing intra-uterine pH. Copper IUD prevents implantation by a direct embryotoxic
effect. Danazol acts as a luteolytic as well as prevents nidation and hampers
decidualization. The GnRH analogues act by inhibiting LH secretion. Failure rate
of Emergency Contraception is varying from 0-2.4% depending on the method used,
interval between coitus and method use and relationship of coitus to ovulation.
But all methods are ineffective once implantation has already occurred, thus these
are not abortifacients. Definition
A woman faced with the prospect of an unplanned and unwanted pregnancy can,
in many cases, avoid the pregnancy by using Emergency Contraception. This term
is used to describe methods which can be used post-coitally to prevent pregnancy
following unprotected sexual act. These are also called ‘morning after’ methods,
but can be effective if used within 3-5 days of sexual exposure. These
have also been called post-ovulatory methods, but need not necessarily be used
following ovulation, and are useful in all phases of cycle. Emergency Contraception
is not synonymus with ‘visiting’ or ‘vacation’ pill since other methods besides
a pill are included in the gamut of EC. A better definition proposed by
Dr Paul van Look from WHO is - “Emergency contraception refers to a particular
type of contraception that is used as an emergency procedure to prevent pregnancy
following unprotected, possibly fertile intercourse”.
Methods
Several scientific methods are available for Emergency
Contraception now and most of these are safe and effective.
High dose Estrogen :
This was the first scientific method introduced in the
1960s. The method consisted of diethylstilbestrol (DES) being given in a dose
of 50 mg per day for 5 days, subsequently dose was reduced to 10 mg per day. Association
of DES with potential effects on female offspring resulted in a discontinuation
of use of DES. Other estrogens like conjugated equine estrogen, ethinyl estradiol
and depot estrogens were also used by various investigators. Though found effective
in preventing pregnancy, high dose estrogen use is associated with a high incidence
of side-effects, specially nausea and vomiting thus women sometimes fail to complete
the prescribed course of treatment. Besides, menstrual pattern is disrupted following
estrogen use and next period can be earlier with heavier flow. After treatment
failure, 10% of pregnancies are likely to be ectopic, thus estrogens alone are
no longer used as Emergency Contraception. Estrogen-Progestogen
combination : In 1972 Yuzpe and his colleagues evaluated
a combined ethinyl estradiol and levonorgestrel pill each containing 50µg ethinyl
estradiol and 0.5 mg of norgestrel, 2 tablets being given twice, 12 hours apart,
within 72 hours of unprotected intercourse. This is commonly known as Yuzpe Method.
This has fewer side-effects compared to high dose estrogen but still about 50%
have nausea and 10-25% vomit. Currently, this is the most popular and easily available
method. Regular dose oral contraceptive pill can be used as post-coital pill in
prescribed dose. Currently available oral pills Mala-D and Mala-N containing 30µg
ethinyl estradiol require 4 tablets to be given twice at an interval of 12 hours.
There is no contra-indication to use of Yuzpe method.
Progestogens : Norgestrel
as well as quingestanol have been tried and shown to be effective over a range
of doses. The side-effects of progestogen only pills are less than combination
pills. In low doses, progestogen may change the menstrual pattern. Current trials
have shown progestogen only pill, containing 0.75mg, levonorgestrel (LNG) given
in 2 doses 12 hours apart within 72 hours of unprotected intercourse, to be more
effective with fewer side-effects compared to yuzpe method.
LNG has also been tried as 2 doses of 0.75mg, 12 hours apart upto 120 hours
after sexual exposure, as well as, as a single dose of 1.5mg, again within 120
hours. The trial results are under publication.
Anti progestogens :
These are anti-implantation agents when given post-coitally,
menses inducers when given in luteal phase and abortifacients when given in early
pregnancy. Several antiprogestogens have been tried. RU486 (mifepristone) has
been found effective in a single dose of 600 mg, 100 mg and 10 mg when used as
emergency contraception. In a comparative trial of RU486 with Yuzpe regimen, side-effects
were less common with mifepristone but menstrual disturbances occurred more often.
Antiestrogens
: Danazol has a direct luteolytic effect. A 400 mg
dose repeated 12 hourly for 2 or 3 doses has been used with lesser side-effects
as compared to Yuzpe regimen. Centchroman
: is an antiestrogen with no progestogenic, androgenic
or antiandrogenic effect. It has been used as two 50 mg tablets given 12 hours
apart within 72 hours. Main side-effect is ovarian enlargement and delay in menstruation
causing confusion and tension. Adequate trials of Centchroman as an effective
emergency contraception are yet to be conducted.
Intra-uterine Device (IUD) :
Insertion of copper-T and copper-7 within 5 days of unprotected
intercourse have been reported as a highly successful method for post-coital contraception.
Copper-T is effective following even multiple coital exposures during a short
interval and when delay is beyond 72 hours, making hormonal methods ineffective.
IUD is particularly suitable for women who would like to continue using it as
a regular contraceptive. Contra-indications to emergency IUD use are the same
as regular use. In young nulliparous women or women with multiple sexual partners,
there is a risk of pelvic inflammatory disease. Sometimes, irregular bleeding
associated with IUD insertion may mask diagnosis of early pregnancy.
Calculation of Efficacy
Since possibility of conception
is not there throughout the menstrual cycle, measuring pregnancy rate following
EC use is not enough as a measure of efficacy. It is more important to calculate
reduction in expected pregnancies. This is also called prevented fraction and
is calculated by formula. 1–observed
pregnancies
-----------------------------------
expected pregnancies
For calculating the expected pregnancies conception risk for each day of menstrual
cycle is calculated by probability of conception on that cycle day. For estimation
of probability of conception, a formula proposed by Wilcox et al is used. The
day of ovulation is calculated by subtracting 14 days from the date of next period
and depending on the day of coitus in relation of this day probability is estimated
(fig. 1) Thus efficacy of EC is expressed in two ways. (1) Overall
pregnancy rate and (2) Pregnancies prevented.
Side-effects
The main problem with hormonal pills is nausea and
vomiting, which is comparatively more with Yuzpe method than LNG alone. To prevent
these, it was advocated to prescribe these drugs with anti-emetics. But, currently,
this is considered unnecessary. Mifepristone has fewer incidences of nausea and
vomiting. The other common side-effect is on the menstrual cycle which may get
pre-poned or post-poned. The amount of blood loss may also be more or less. Menstrual
delay is seen more often following use of mifepristone.
No increase in the risk of thrombo-embolic disorders is observed.
Contra-Indications :
Pregnancy is the only contra-indication to use of EC.
Effect on pregnancy
Emergency contraception is capable
of preventing 75-99% of pregnancies which would have occurred if no contraceptive
was used. Thus 1-2% of women using these methods may conceive. It is desirable
to have abortion facilities available for these patients. But, if a woman elects
to continue the pregnancy, there is no direct detrimental effect of these methods
on blastocyst and no increase in the risk of fetal malformations. There is no
increase in the risk of ectopic pregnancy.
A comparison of different methods is presented in the table below.
Conclusion
The use of Emergency Contraception is required by
women who experience unprotected sex for whatever reason. There is a short time-frame
of efficacy for these methods (upto 120 hours). Once implantation has occurred,
these methods are ineffective. EC is safe and effective averting 75-99% of
expected pregnancies, thereby reducing the risks of undergoing an abortion or
agony of carrying an unwanted pregnancy. It should be clear that EC is a one-time
procedure. Regular use of effective contraception should be encouraged after onset
of periods. | 
