What is this?
Oral contraceptives, commonly known as birth control pills, are hormone-based medications taken orally to prevent pregnancy. They work by inhibiting ovulation and by preventing sperm from passing through the cervix.
Oral contraceptive pills (OCPs) come in two types: combined estrogen-progesterone pills (also known as combined oral contraceptive pills or COCs) and progesterone-only pills (POPs).The most frequently prescribed pill is the combined oral contraceptive (COC) pill. In this pill, progesterone prevents pregnancy, while the estrogen component helps regulate menstrual bleeding.
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The
effectiveness of oral contraceptive pills (OCPs) depends on how they are used.
With perfect use, where the pills are taken consistently and correctly every
time, fewer than one woman out of 100 will become pregnant in the first year.
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However,
with typical use, which includes occasional inconsistencies or incorrect usage,
the failure rate increases to 9 women out of 100 becoming pregnant in the first
year. Due to human error, the failure rate for combined oral contraceptive
(COC) pills is typically around 9%.
While most women take
OCPs to prevent pregnancy, 14% use them for non-contraceptive purposes. OCPs
can be used to manage various health conditions, particularly menstrual-related
disorders such as menstrual pain, irregular menstruation, fibroids,
endometriosis-related pain, and menstrual-related migraines.
How does this work?
The primary mechanism
of action of oral contraceptive pills is the prevention of ovulation. They
inhibit follicular development and prevent ovulation. Progestogen provides
negative feedback to the hypothalamus, reducing the pulse frequency of
gonadotropin-releasing hormone (GnRH). This, in turn, lowers the secretion of
follicle-stimulating hormone (FSH) and decreases luteinizing hormone (LH)
levels. Without follicle development, there is no increase in estradiol levels
(which are produced by the follicle). The progestogen's negative feedback,
combined with the lack of estrogen's positive feedback on LH secretion,
prevents the mid-cycle LH surge. As a result, ovulation is prevented since no
follicle develops and no LH surge occurs to release the follicle.
Estrogen also helps
inhibit follicular development through negative feedback on the anterior
pituitary, which slows FSH secretion, although its effect is not as prominent
as that of progesterone. Another key mechanism is progesterone's ability to
make cervical mucus hostile to sperm, preventing them from penetrating through
the cervix and upper genital tract. Additionally, progesterone-induced
endometrial atrophy helps deter implantation.
Efficacy:
The effectiveness of
OCPs depends on the consistency and correctness of their use:
○
When
used consistently and correctly every time, fewer than 1 woman out of 100 will
become pregnant in the first year.
○
With
typical use, which may include occasional inconsistencies or incorrect usage,
the failure rate is about 9 women out of 100 becoming pregnant during the first
year.
Due to human error,
the typical failure rate for combined oral contraceptive (COC) pills is
typically around 9%.
Usage duration recommended:
Combined Oral
Contraceptive Pills (COCs)
Choice of COC:
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Typically
contain less than 50 mcg of ethinyl estradiol.
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Can
be monophasic (same dose in all active pills) or multiphasic (varying doses).
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Prescribed
as cyclic (monthly bleeding), extended cyclic (bleeding every 3 months), or
continuous dosing (no bleeding).
Formulations:
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Cyclic: 21-24 days of active pills followed by 4-7 days of
hormone-free pills.
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Extended Cycle: 3 months of active pills followed by a placebo week.
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Continuous Use: Only active pills used for 1 year, stopping all menstrual
bleeding. Monophasic pills are easiest to manipulate for this method.
Initiation:
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Take
at the same time each day.
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First-day
start: Start on the first day of menses.
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Quick
start: Start any day; use additional contraception for the first 7 days.
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Sunday
start: Start on the first Sunday after the period begins; use additional
contraception for the first 7 days.
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Post-abortion/pregnancy
loss: Start within 7 days.
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Postpartum:
Avoid for the first 21 days due to risk of venous thromboembolism (VTE). Higher
risk women should avoid for 42 days. Breastfeeding women should avoid it for 42
days.
Missed Doses:
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If a
tablet is missed, take it as soon as remembered and the next tablet at the
usual time (two pills in one day).
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If
two tablets are missed in the first or second week, take two tablets the day
remembered and two the next day, then resume one per day. Use additional
contraception until a new cycle starts.
Emergency Contraception:
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Recommended
if unprotected intercourse occurs and two or more pills are missed in the first
week of the cycle.
Progesterone-Only Pills (POPs)
Choice of POP:
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Suitable for women who cannot use estrogen.
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Norethindrone
taken continuously with no hormone-free pills.
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Drospirenone
includes 24 hormone pills and 4 hormone-free pills.
Initiation:
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Take
at the same time each day.
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If
starting more than 5 days from the onset of menses, use backup contraception
for the first 48 hours.
Missed Dose:
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If
missed by more than 3 hours, or if vomiting/severe diarrhea occurs within 3
hours, take the missed pill as soon as remembered and the next pill at the
scheduled time. Use additional contraception for 48 hours.
Emergency Contraception:
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Recommended
for unprotected intercourse within 48 hours of starting POP or missed pills if
backup contraception was advised.
Side effects of oral contraceptive pills can include:
If you experience
severe or persistent side effects, it's important to consult your healthcare
provider.