How contraceptives work

Oral contraceptive pills help women control their entry into motherhood

couple at home & woman talking on the phoneOral contraceptive pills [OCs] are available in two varieties: Combination pill and Progesterone-only pill.

Combination pills

Combination pills contain both oestrogen and progesterone.

How do they work?

These pills prevent pregnancy by thickening the cervical mucus [the substance at the opening of the uterus]. This makes it extremely difficult for the sperm to reach and fertilise the egg. Combination pills also hamper the process of ovulation [release of egg by the ovary].

How to take them?

You will have to take the pill for 21 days regularly at the same time every day. The first pack should be started on day one of the bleeding [unlike day five as advocated earlier] and should be taken for 21 days.

A gap of seven days is given [during which the menstruation will happen]. On the eighth day, the next packet of oral contraceptive pills should be started.

If you miss a pill

If a pill is missed, then it should be taken as soon as you remember it and continue taking the next pill at its scheduled time. If two consecutive pills are missed, continue taking the subsequent pills but for the next seven days use additional contraception such as a condom. Missing/skipping pills alters the hormone levels thus raising your chance of conception.


Some women experience side-effects like nausea, headache, breast tenderness, bloating, water retention and mood changes. Women who smoke, have hypertension, blood clotting disorder or certain medical problems like cancer of the breast, or liver disorders, are advised against oral contraceptive pills.

Progesterone only pill [POP]

Progesterone only pills are designed for breast feeding women as combination pills alter the quality and quantity of milk and hence are not recommended. POPs do not affect the milk production and the baby.

How do they work?

These pills prevent pregnancy in three ways. First, they trick the body into believing it is already pregnant and hence not ovulate. Second, it makes the uterus environment unsuitable for conception. Third, it thickens the mucus between your uterus and your vagina such that it becomes almost impossible for the sperm to penetrate through it and reach the egg.


The advantages of using these pills are that it helps in clearing up acne, eases premenstrual syndrome [PMS], protects against endometrial and ovarian cancer, and of course, prevents pregnancy.


The major disadvantage is that they do not prevent sexually transmitted diseases [STDs].

How to take them?

These pills should be started at least two weeks after the lactation is established. These have to be taken every day and at the same time of day.

There is no pill-free period. Once the infant is weaned off the mother’s milk, combination pills can be started. The only major disadvantage of progesterone only pills is spotting, which is unpredictable.

Drug interaction

Patients who are taking medications like Rifampicin, barbiturates, oral anti-coagulants or have vomiting and diarrhoea, are advised contraceptive methods other than OCPs.


Rekha Agrawal
Dr Rekha Agrawal is a gynaecologist at Lilavati Hospital and Research Centre, Mumbai.


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