Many designs of IUD have been tried in different countries over the years. Some have never reached widespread production; others have been used and later withdrawn from the market for reasons such as increased risk of infection or septic. The most commonly-approved IUDS are the Lippes Loop (one of the earliest types, and still used by more women worldwide than any other type), the Saf-Tcoil, the Copper-T, the Copper-7, and the Progestasert-T. The Copper-T and Copper-7, as their names imply, are IUDS which have wrappings of copper wire. The Progestasert-T is a progestogen-elaborating IUD. All the above styles are fitted with threads that hang down through the cervical canal and into the vagina. These help to reassure the woman that the nm is still correctly in place, and also facilitates removal of the IUD if necessary. Generally practitioners prefer to use IUDS with tails, except in China where a particular tail-less model is popular.
How it works
For some years there was doubt as to just how an IUD worked. Researchers soon began to agree on one main effect, which is that in some way the IUD prevents implantation of a fertilized ovum. This could happen because of a local inflammation of the uterus; because of localized hormonal changes; because of a chemical imbalance affecting the endometrium; because of disruption of the normal hormonal pattern needed to sustain pregnancy; or because of mechanical disruption of the implanted blastocyst. It is also possible that the transport of the ovum down the fallopian tube may be accelerated, so that the blastocyst reaches the uterus before it is ready to implant. In addition it is possible that in some way the IUD immobilizes the sperm as they pass through the uterus and makes them incapable of fertilizing an ovum. However the incidence of pregnancy andpregnancy in IUD users makes this unlikely, as do recent animal tests which have shown that animals fitted with IUDS conceive numerous foetuses which can then be flushed out of their uteri.
It also seems certain that IUDS have no effect whatsoever on ovulation. The generally-accepted explanation for the IUD’S effect is that it stimulates an inflammatory reaction in the uterus, which prevents the fertilized egg from implanting. This inflammation is sterile, that is, it is not associated with bacteria or viruses. Copper seems to stimulate this reaction, which explains the greater effectiveness of the IUDS which contain copper.
Before being fitted with an IUD, various checks will be made. Details are taken of the woman’s menstrual history (e.g. whether her periods are light, heavy, irregular, painful) and also of her fertility history (whether she has ever had a child, an abortion, a miscarriage, an ectopic pregnancy). She will also be asked whether she has ever had pelvic inflammatory disease (Pm), if she has a history of IUD expulsion, and whether she intends ever to have any (more) children.
IUDS cannot be used in women with very small uteri, and women with an allergy to copper cannot use the Copper-T or Copper-7. Damage to the uterus or cervix during a previous childbirth may make an IUD undesirable. Also, some doctors prefer not to fit IUDS in women who have had caesarians, as there may be a likelihood of the IUD perforating the uterus through the old scar; other doctors are happy to fit IUDS to those patients provided at least three months have passed since the operation. IuDs should not be fitted if there is undiagnosed irregular bleeding, a history of PID, or large numbers of— these can alter the contours of the uterus and make the IUD ineffective. Some doctors prefer not to fit IUDS to women on anticoagulant or steroid therapy, or women with chest disease, some heart conditions, or renal disease. Any patient with anaemia should be treated before fitting, as most IUDS increase menstrual flow.
There is some disagreement over whether IUDS should be fitted in women who have never had children. The general consensus in this country is that they should not, as fitting is more difficult and there is an increased risk of ND with IUDS, which can cause future infertility. Other countries, and some individual clinics in this country, are prepared to fit IUDS in women who have never had children.