7. Contraception (lecture) Flashcards
what is the effect of oestrogen in early / middle follicular phase (before ovulation) on HPG axis?
negative feedback on anterior pituitary and hypothalamus (inhibit GnRH, LH, FSH)
effects of oestrogen on HPG axis at ovulation?
positive feedback on anterior pituitary (LH surge) and hypothalamus (GnRH)
effect of progesterone on HPG axis at lower doses?
progesterone doesn’t inhibit LH surge, ovulation still likely
progesterone will THICKEN cervical mucus
what happens at moderate / high dose of progesterone at ovulation?
(corpus luteum release progesterone, HIGH oestrogen)
progesterone inhibits the positive feedback of oestrogen –> NO LH surge, NO ovulation
what happens at moderate / high dose of progesterone on the HPG axis at early / mi-follicular phase? (before ovulation)
progesterone enhances NEGATIVE feedback of natural oestrogen - reducing LH and FSH secretion
(low oestrogen, negative feedback)
what are common methods of contraception?
natural barrier prevention of ovulation inhibition of sperm transport inhibition of implantation sterilisation (permanent)
what are the natural methods of contraception?
fertility awareness methods
lactational amenorrhoea method
what is fertility awareness method of contraception? (natural)
use of fertility indicators to identify fertile and infertile points of the menstrual cycle. using:
cervical secretions
basal body temperature (higher post ovulation)
length of menstrual cycle (when day 14 is approx.)
what are the advantages of using natural methods of contraception?
no hormones no contraindications (no drug harms)
what are the disadvantages of using natural methods of contraception?
not as effective
unreliable
what is the lactational amenorrhoea method of contraception? (natural)
breastfeeding delays the return of ovulation after childbirth
how long is the lactational amenorrhoea method of contraception effective for? (natural)
only effective up to 6 months after birth
what are the barrier methods of contraception?
male / female condoms
female diaphragm / cap
what is the mechanism of action male / female condoms? (barrier)
prevents entrance of sperm into the cervix
what is female diaphragm / cap also used with? (barrier)
diaphragm / cap also used with spermicide so additional CHEMICAL barrier
advantages of barrier contraception?
can help prevent STIs
can be inserted anytime before intercourse
disadvantages of male condom (barrier contraception)?
sensitivity / allergy to latex
disadvantages of female condom (barrier contraception)?
not as widely available
what is a disadvantage of barrier contraception?
need to use with spermicide (can cause a local reaction)
what are the different pills used for prevention of ovulation?
combined oral contraceptive pill (COCP)
progesterone depot
progesterone implant
why do progesterone pills work as a contraception?
at moderate / high doses, progesterone inhibits the positive feedback of oestrogen - no LH surge, no ovulation
(lower doses progesterone thickens cervical mucus, so progesterone needs to be high enough)
what is progestogen?
synthetic form of progesterone
what is the principle action of combine oral contraceptive pill (COCP)?
prevents ovulation
what are the secondary actions of COCP?
Reduces endometrial receptivity to inhibit implantation
Thickens cervical mucus to inhibit penetration of sperm
what are the advantages of COCP?
can relieve menstrual disorders
reduces risk of ovarian cysts and cancer (compared to just oestrogen)
disadvantage of COCP?
user dependent
side effect of COCP?
breakthrough bleeding
breast tenderness
mood disturbance
what can COCP lead to increased risk of?
venous thromboembolism (clot in veins) myocardial infarction
how do you take COCP?
taken either 21 days followed by 7 day break
OR
taken for 21 days with 7 days of ‘dummy’ pill
what are progesterone depot AND progesterone implant’s main mechanism of action?
prevents ovulation
what are progesterone depot AND progesterone implant’s secondary actions?
Reduces endometrial receptivity to inhibit implantation
Thickens cervical mucus to inhibit penetration of sperm
what are the advantages of progesterone depot?
convenient
can also relieve menstrual disorder
what are the disadvantages of progesterone depot?
Altered and irregular bleeding is common
Delayed return of fertility for up to 1 year after stopping
Not quickly reversible
Small loss of bone mineral density and and possible increase in fracture risk
what is progesterone depot?
synthetic progestogen
how is progesterone depot administered?
via subcutaneous / IM injection, which is slowly released into systemic circulation
how long does an injection of progesterone depot last for?
between 8-13 weeks
what are the advantages of progesterone implant?
long duration of action
convenient
can also relieve menstrual disorders
what are the disadvantages of progesterone implant?
small procedure required to fit and remove the implant
local adverse effects can occur
can cause changes in bleeding pattern
how does progesterone implant work?
progestogen containing 4cm flexible rod implant which si inserted sub-dermally (under the skin) in the upper arm
how long can progesterone implant last up to?
3 years
