Intrauterine contraceptive devices

Question 1

Intrauterine contraceptive devices

Effectiveness

Answer 1

Intrauterine contraceptive devices comprise both conventional copper intrauterine devices (IUDs) and levonorgestrel-releasing intrauterine systems (IUS, Mirena). The IUS is also used in the management of menorrhagia

Mode of action:

• IUD: primary mode of action is prevention of fertilisation by causing decreased sperm motility and survival (possibly an effect of copper ions)
• IUS: levonorgestrel prevents endometrial proliferation and causes cervical mucous thickening

Question 2

Intrauterine contraceptive devices

IUD is effective immediately following insertion
IUS can be relied upon after 7 days

Potential problems

Answer 2

Potential problems:

• IUDs make periods heavier, longer and more painful
• the IUS is associated with initial frequent uterine bleeding and spotting. Later women typically have intermittent light menses with less dysmenorrhoea and some women become amenorrhoeic
• uterine perforation: up to 2 per 1000 insertions
• the proportion of pregnancies that are ectopic is increased but the absolute number of ectopic pregnancies is reduced, compared to a woman not using contraception
• infection: there is a small increased risk of pelvic inflammatory disease in the first 20 days after insertion but after this period the risk returns to that of a standard population
• expulsion: risk is around 1 in 20, and is most likely to occur in the first 3 months