Mirena: The new generation coil

Dr Brigid Monda

Mirena is a hormone-releasing coil. It was initially developed for women with abnormal uterine bleeding who did not want their uteruses removed for various reasons like still wanting to have children or being poor candidates for surgery. Today, the list of uses and benefits of Mirena has grown immensely.

Like its cousins, Mirena is made of a flexible piece of T-shaped white plastic with a single strand of strong, smooth plastic string attached to its end that allows for its easy removal. The string also allows a woman or her doctor to tell if the coil is still in the correct position by either feeling or visualising it. Unlike its cousins though, Mirena has no copper but instead carries a cylinder on its stem that contains a synthetic hormone, Levonorgestrel.

Levonorgestrel is a type of progesterone used in some types of pills. Mirena continuously releases the hormone into the uterus with very little entering the blood stream, and prevents pregnancy for up to five years.

It is inserted through the vagina into the uterus in a procedure that takes only minutes. Once inserted, the coil is immediately effective and when removed (by a doctor), its contraceptive effect is immediately reversed. It can also be inserted at any time during the cycle but preferably during one’s period when the cervix is open.

How it works

It prevents pregnancy very effectively by releasing the hormone in its cylinder into the uterine cavity. This hormone thickens the cervical mucus plug, which prevents sperm from entering the uterus and thins the lining of the uterus, which prevents any fertilised egg from implanting in it. It also creates a very hostile environment in the whole upper reproductive tract making it difficult for sperm to move about in the uterine cavity and in the tubes. The hormone in the Mirena may sometimes stop ovulation.

Advantages

Mirena gives you the advantages of the coil and those of hormonal contraception like the pill without the side effects of either. It also has a long list of non-contraceptive benefits, namely;

• Very cost-effective because it gives you long term contraception after a just one insertion.

• Is as effective as a bilateral tubal ligation (BTL) giving women who do not want any more babies and have no desires for a BTL.

• Convenient because you don’t have to remember to swallow a pill daily.

• Is safe and private.

• Prevents period pains.

• Thins the lining of the uterus dramatically reducing the number of days and amount of blood lost during one’s periods. Aneamic women can vouch for this one.

• Protects against Pelvic Inflammatory Disease (PID) and ectopic pregnancies because it reduces the amount of bleeding and thickens the cervical mucus plug preventing both sperm and bacteria from ascending into the upper parts of the reproductive tract.

• Protects against cancer of the uterus because of its effect on the lining of the uterus

• Its contraceptive effect takes place before fertilisation so it cannot be regarded as a cause of abortions like the other coils sometimes are.

• Can be used by breast-feeding mothers and women who cannot use estrogen-containing birth control pills because its hormonal effects are limited to where it is needed — in the uterine cavity.

• Can be inserted immediately following the delivery of a baby, immediately after an abortion or immediately after removal of another coil.

• There is no delayed return to fertility. A woman using Mirena is able to conceive soon after removing the coil.

• Can be used in women who have painful and heavy periods due to endometriosis, adenomyosis, fibroids or those who have inherited bleeding disorders.

• Its long-term use reduces the incidence of fibroids, related heavy periods and fibroid related surgery

• Can be used as part of Hormone Replacement Therapy for postmenopausal women.

Disadvantages:

• It is expensive compared to other long-term methods of contraception because the initial cost of insertion is high.

• Your partner may feel the strings during intercourse.

• It does not protect you against STDs like HIV.

• One may develop a functional ovarian cyst.

• There may be spotting in between periods, especially during the first few months.

• A small percentage of women completely stop having periods after using Mirena for a year, which may worry the affected women but for doctors, this is a positive health benefit because it protects against anaemia.

• Accidental puncturing of the uterus during insertion.

• There is a slight risk of infection during insertion.