Progestin-only Birth Control: Benefits and Side Effects

The main difference between the progestin-only birth control pill and other oral contraceptives is that it doesn't contain estrogen, which an advantage for women who avoid this component out of preference or because they believe it affects their health.
Progestin-only Birth Control: Benefits and Side Effects

Written by Edith Sánchez

Last update: 27 May, 2022

The minipill is an oral contraceptive that contains a lower dose of hormones than the traditional birth control pill. It’s also known as the progestin-only birth control pill, as it doesn’t contain estrogen, like others.

It’s a small pill that, if used perfectly, is 99% effective in preventing pregnancy. However, it’s difficult for anyone to reach such a degree of perfection in its use. So, the normal degree of effectiveness of the mini-pill is 91%.

How does progestin-only birth control work?

A woman looking at birth control pills.
The minipill suppresses ovulation with a lower hormonal dose than traditional contraceptives.

Like other oral contraceptives, the minipill prevents ovulation. This means that its effect prevents the release of eggs. Of course, if there aren’t any eggs, then pregnancy can’t occur.

The mini-pill is less effective than traditional contraceptives in suppressing ovulation. However, it has two other effects that not only make up for that deficiency but also increase its effectiveness in preventing conception.

These effects are as follows:

  • They cause the mucus in the cervix to become very thick. This makes it very difficult for the sperm to pass through it and reach the fallopian tubes to fertilize the egg.
  • It thins the lining of the uterus. This means that if the sperm were to fertilize the egg anyway, implantation in the uterus would be very difficult and would make it unlikely that pregnancy would take place.

With a few specific exceptions, the minipill can be used by any woman. It’s often used especially by mothers who are breastfeeding, as there’s an idea that traditional contraceptives inhibit breast milk production, although there’s no evidence for this.

A doctor’s likely to recommend the use of the mini-pill when a woman has a history of blood clots in her legs or lungs. The same measure’s taken if there’s a risk of developing such clots, even if you haven’t had them.

Read also: All About Male Birth Control Methods

Some women are wary of contraceptives containing estrogen because of possible side effects. In such cases, the mini-pill could be an alternative. It may also be prescribed when a woman has dermatitis associated with the menstrual cycle.

How should the minipill be taken?

Ideally, it’s best to start taking the pill on the first day of your period, as this will have a greater contraceptive effect. If making the switch from traditional oral contraceptives, the change is made without interrupting daily intake. In other words, the day after taking the last conventional pill. For the minipill to be effective, the following guidelines should be applied:

  • Take one pill at the same time every day. If this isn’t possible, it’s best to maintain a time lag of no more than three hours.
  • The daily intake should never be interrupted. It’s important to get the prescription well in advance so that this doesn’t happen.
  • If you’re not able to start taking the pill on the first day of your period, then you should use condoms during the following seven days, if sexual intercourse takes place.
  • Women who are breastfeeding can use the minipill from the sixth week after delivery.
  • If you’ve been using an injectable contraceptive, then the correct thing to do is to start taking the minipill on the day your next injection was to be given.

What to do if I forget to take it one day?

If a woman forgets to take this pill at the usual time, she should take it as soon as she can. Ideally, she should always carry it with her so that she can take it at any time, even if she’s away from home.

If more than three hours have passed since you were supposed to take the pill, the best thing to do is to take it as soon as possible. In addition to this, use a condom for sexual intercourse during the following two days. If you forget to take the pill for more than 12 hours, then you’ll need to use a condom during the following seven days.

A woman holding up a calendar of her menstrual cycle.
If you miss a pill,, you’ll need to combine the minipill with the use of a condom.

Advantages of progestin-only birth control

The main advantage of the minipill is that it doesn’t contain estrogen, unlike other oral contraceptives. This is ideal for women who don’t want to ingest these hormones, either out of preference or because of health problems.

Other advantages of this type of contraceptive are that they:

  • Are more effective than barrier methods, such as condoms and diaphragm.
  • Usually, generate fewer side effects than conventional oral contraceptives.
  • Are safe to use during breastfeeding.
  • Don’t require the interruption of sexual intercourse to use them.
  • In some women, they make the menstrual cycle more regular, shorter, lighter, and less painful.
  • It’s a temporary method of contraception, meaning you can discontinue it at any time and it doesn’t affect fertility.

Disadvantages of the minipill

Minipills also have disadvantages.

The first of these is the requirement for discipline. This is because, for them to reach 99% effectiveness, they must be taken every day at the same time, which could be overwhelming for some women.

Other disadvantages are the following:

  • In some women, it may generate irregular menstrual periods. In other words, the absence of a period or eventual spotting between periods.
  • It may cause mood swings. Some women lose interest in sex.
  • May cause weight gain in some cases.
  • They don’t protect against sexually transmitted diseases. If there’s uncertainty about the safety of your sexual partner, it’s best to combine the use of the pill with condoms.
  • Some people experience headaches and/or nausea when using this type of pill.

Contraindications and adverse effects of the minipill

The failure rate of the minipill is somewhat higher than that of classical oral contraceptives. An estimated that 13 out of 100 women using this method become pregnant per year.

There’s a slightly higher risk of ectopic pregnancy, or pregnancy outside the uterus, when using the mini-pill and becoming pregnant. However, no link has been found between this method and birth defects in the baby.

The use of the minipill isn’t advisable for women who meet the following criteria:

  • Have suffered from breast cancer
  • Experience uterine bleeding with no known cause
  • Have liver disease
  • Take medication for seizures, HIV/AIDS, or tuberculosis
  • Have difficulties fully complying with the daily intake at the same time

Progestin-only birth control: Yes or no?

This contraceptive method becomes more effective the more discipline is applied to its use. Among women who take the pill at the same time every day and never forget to do so, there’s only one pregnancy per 100.

If you start taking the minipill and notice any adverse reactions or health problems, the best thing to do is to consult your doctor as soon as possible. It’s likely that this method isn’t right for you.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Franco, Y., Mendoza-Fernández, V., & Lemini, C. (2003). Mecanismos de acción de los efectos protectores de los estrógenos sobre el sistema cardiovascular. Rev Fac Med UNAM, 46(3), 101-8.
  • PRATS, E. C., & FERNÁNDEZ, V. J. B. (2004). Anticonceptivos orales. Offarm, 23(9).
  • Monterrosa, A. (2006). Anticonceptivos orales de sólo progestina. Revista Colombiana de Obstetricia y Ginecología, 57(1), 45-53.
  • Dr. Rafael Sánchez Borrego. Dr. Oscar Martínez Pérez. GUÍA PRÁCTICA EN ANTICONCEPCIÓN ORAL Basada en la evidencia.
  • Organización Mundial de la Salud. Planificación Familiar.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.