Birth control pills prevent pregnancy through
several mechanisms, mainly by stopping ovulation.
If no egg is released, there is nothing to be
fertilized by sperm, and the woman cannot get
pregnant. Most birth control pills contain synthetic
forms of two female hormones: estrogen and
progestin. These synthetic hormones stabilize a
woman's natural hormone levels, and prevent
estrogen from peaking mid-cycle. Without the
estrogen bump, the pituitary gland does not
release other hormones that normally cause the
ovaries to release mature eggs.
Specifically, synthetic estrogen in the pill works to: lace top wedding dress
Stop the pituitary gland from producing follicle
stimulating hormone (FSH) and luteinizing
hormone (LH) in order to prevent ovulation.
Support the uterine lining (endometrium) to
prevent breakthrough bleeding mid-cycle.
Meanwhile, synthetic progestin works to:
Stop the pituitary gland from producing LH in
order to prevent egg release.
Make the uterine lining inhospitable to a
fertilized egg.
Partially limit the sperm's ability to fertilize
the egg.
Thicken the cervical mucus to hinder sperm
movement (although this effect may not be key
to preventing pregnancy).
There are two kinds of hormonal birth control pills:
(1) the combination pill which contains estrogen and
progestin and (2) the progestin-only pill (known as
the minipill). Combo pills are significantly more
effective than progestin-only pills and have the
added benefit of less breakthrough bleeding.
However, some women cannot tolerate estrogen and
prefer the progestin-only pill. Both types of pills
are available in several different brands, each of
which have slightly different blends of hormones.
These two kinds of hormonal birth control are
available in other forms besides pills. The
combination formula is also available as a patch and
a vaginal ring. The progestin-only formula is also
available in intramuscular shots (Depo-Provera), an
implant (Implanon), and in intrauterine devices
(the Mirena IUD).
Some women may prefer these other forms of
hormonal birth control because they can be taken
less often (and consequently are easier to
remember). While birth control pills must be taken
everyday, the patch is only applied once per week,
the vaginal ring only once per month, and the
intramuscular shot only once every 3 months. An
IUD is inserted into the uterus and can prevent
pregnancy for five years or more. In the US,
hormonal birth control pills and devices are only
available by prescription. Women may want to ask a
gynecologist or women's health care provider for
information about different kinds of birth control,
including which methods would be best for them
personally.
If you choose birth control pills (which are
sometimes the cheapest form of birth control), it
is very important to take the pills at the same
time everyday. This creates a more stable level of
hormones in your body. When you forget your pill
(or take it three to four hours late or more), this
causes a dip in your body's levels of the birth
control hormones. If you forget your pill one day,
you may need to take two pills the next day, which
will cause a spike in your body's levels of the birth
control hormones. To maximize protection against
pregnancy and to minimize side effects, pick a
time you are likely to remember (maybe first
thing in the morning or right before bed) and take
your pill this same time everyday.
Finally, birth control pills traditionally come in
packs of 21 or 28 pills. Both types of packs contain
21 active pills. The seven extra pills in the 28-pill
pack are placebo pills which are there to remind
you to continue taking one pill everyday and to
remind you when to begin the next pack. Whether
you take placebo pills or simply wait 7 days to
start the next pack, the 7-day break from
hormones triggers monthly bleeding that mimics a
woman's menstrual period. Women are still
protected from pregnancy during this time as long
as they have taken all the active pills consistently
and correctly. For more details, take a look at Why
do I menstruate while on birth control? in Go Ask
Alice! archive for Sexual Health.
Newer brands of birth control pills have been
approved by the U.S. Food and Drug Administration
(like Seasonale) which allow women to have their
"period" fewer times per year. Seasonale packs
come with 84 active pills followed by a placebo week
so the woman bleeds only 4 times per year. For
more info, check out Delaying your period through
oral contraceptives (link is external)
in the Go Ask Alice! Sexual and Reproductive
Health archive. If you're interested in using
hormonal birth control, speak with your health care
provider about which method would suit you best.