Intrauterine devices
Intra uterine devices are the contraceptive method most widely used in the developing countries and in the family planning programmes of the WHO (World Health Organization).
“A whole range of intrauterine devices currently exists in various forms, made of plastic (T-shaped or crow’s foot) or metallic (copper or other metals). They are inserted non-traumatically through the cervix in the uterine cavity. T-shaped IUDs may contain a progestogen substance in their horizontal arm, which is released slowly into the uterine cavity. When the IUD is introduced into the uterus, it is deployed in the cavity like an umbrella and anchors itself to the wall, remaining linked to the outside by a thin plastic wire, allowing for its removal two to five years after introduction. Sometimes the IUD fails to prevent the implantation of the embryo and a pregnancy develops: the IUD can then be removed under ultrasonic control by delicate traction on its ‘tail’, allowing the pregnancy to continue without risk to the baby, but as it is a delicate operation, it is more prudent to leave the IUD in situ and not remove it until after delivery”.
“Unfortunately, in both cases the risk of spontaneous abortion during pregnancy is far higher (around 50 %,) than under normal conditions (around 12%)”.
- “The IUD does not prevent fertilization, given that it is criticized for being responsible for ectopic pregnancies.
- The IUD acts through a mechanical effect, which is always present. Insertion of the IUD triggers a reaction to a foreign body in the mucus membrane of the uterine cavity, probably giving rise to uterine contractions and irritation of the endometrium, making the uterus unfit for nidation. It can be deduced that the IUD prevents nidation of the embryo and hence acts as an abortifacient.
- The IUD causes chronic endometritis. The inflammatory reaction in tissues in the area in contact with the coil releases products of cellular decomposition of white corpuscles and endometrial cells, whose action is prejudicial to spermatozoa and the fertilized egg, which is unable to implant in an endometrium ‘in disorder’.
- The presence of the IUD also causes the release of prostaglandin in the endometrium, increasing the contractile activity in the fallopian tubes and uterine body. This hinders the ascent of spermatozoa and prevents implantation of the fertilized egg.
- The presence of copper in some IUDs has the additional effect of increasing secretion and fluidity in the endometrial mucus. This fluidization prevents implantation of the blastocyst, which then tends to wander along the uterine walls without being able to make stable contact. There is also a reduction in the sensitivity of the endometrial cells to the action of oestrogens. Finally, copper exerts a toxic effect on spermatozoa.
- In IUDs containing progestogens, the mechanical effect is combined with a hormonal effect. 18 hours after insertion of an IUD in the uterus, superficial endometrial atrophy can be observed, which prevents implantation of the blastocyst. Here again, the abortive action of the intrauterine device is potentiated. An embryo unable to implant is expelled in the next menstruation. The woman will not realize she has been pregnant because the expulsion happens very early. A pregnancy test at this stage will be negative because there has been no placental development”.