Repro: Contraception

Question 1

What is the difference in oestrogen feedback roles at low and high levels?

Answer 1

Low levels of oestrogen has a negative feedback role so this reduces FSH and LH secretion.
High levels of oestrogen has a positive feedback role causing an LH surge

Question 2

What are the different feedback roles of progesterone at low and high doses?

Answer 2

At high doses progesterone enhances the negative feedback of oestrogen and inhibits positive feedback of oestrogen.
At low doses of progesterone the LH surge is not inhibites. Low progesterone thickens cervical mucus

Question 3

What are the 2 natural methods of contraception?

Answer 3

Fertility awareness: monitoring cervical secretions, basal body temp (higher at ovulation) and the length of the menstrual cycle to monitor infertile points of the cycle.

Lactational amenorrhoea: breastfeeding full time up to 6 months after birth prevents pregnancy. The prolactin suppresses GnRH release

Question 4

What are the 2 methods of barrier contraception?

Answer 4

Male and female condoms: prevent entrance of sperm into the cervix
Female cap: need to use alongside spermacide

Question 5

Which methods of contraception prevent ovulation? How does this work?

Answer 5

The COCP, progesterone depot (IM injection) and progesterone implant.
The high levels of progesterone inhibits positive feedback of oestrogen therefore there is no LH surge

Question 6

What are the secondary actions of the COCP, progesterone implant and depot?

Answer 6

Reduces endometrial receptivity to implantation

Thickens cervical mucus to inhibit penetration of sperm

Question 7

Which methods of contraception inhibit sperm transport? How does this work?

Answer 7

The progesterone only pill. Contains a lower dose of progesterone which does not inhibit LH surge however thickens cervical mucus making it impenetrable to sperm.

Question 8

Which methods of contraception inhibit implantation? How does this work?

Answer 8

Two types of coil: intrauterine system which contains progesterone and intrauterine device which contains copper.
IUS: progesterone reduces endometrial proliferation which prevents implantation
IUD: copper is toxic to sperm and ovum. Can also be used as emergency contraception up to 5 days after unprotected intercourse

Question 9

What are the permanent methods of contraception?

Answer 9

Vasectomy: local anaesthetic procedure where the vas deferens is cut or clipped.

Tubal ligation: local or general. Fallopian tubes are cut or clipped.

(NB the clips can fall off 2/1000 cases)