[1] A previous model known as the Dalkon shield was associated with an increased risk of pelvic inflammatory disease (PID).

However, current models do not affect PID risk in women without sexually transmitted infections during the time of insertion.

[21] The progestogen released from hormonal IUDs mainly works by thickening the cervical mucus, preventing sperm from reaching the fallopian tubes.

They also cause the uterus and fallopian tubes to produce a fluid that contains white blood cells, copper ions, enzymes, and prostaglandins, which is also toxic to sperm.

[22] The very high effectiveness of copper-containing IUDs as emergency contraceptives implies they may also act by preventing implantation of the blastocyst.

Their primary mechanism of action is inducing a local foreign body reaction, which makes the uterine environment hostile both to sperm and to implantation of an embryo.

[46] Hormonal IUDs (referred to as intrauterine systems in the UK) work by releasing a small amount of levonorgestrel, a progestin.

Some of these side effects include bleeding pattern changes, expulsion, pelvic inflammatory disease (especially in the first 21 days after insertion), and rarely uterine perforation.

[57] Despite reports, as of 2023, there is no scientific agreement on whether using a menstrual cup increases the risk of IUD expulsion; more rigorous studies are needed.

[59] Modern IUDs do not lead to infertility or make it harder for a woman to become pregnant, and fertility typically returns within days of removal.

Some prior studies found an association between infertility and the Dalkon Shield, an early IUD design which is no longer available.

According to the CDC, benefits generally outweigh the risks, and IUDs are recommended for young and nulliparous women, although more careful attention may be required.

There is a condition known as polycystic ovarian syndrome (PCOS) which causes women to miss their periods and can lead to an increased risk of endometrial cancer.

[68] The use of intrauterine lidocaine (paracervical block) is underutilized in the United States as an effective method to reduce pain associated with insertion.

[76] A suction cervical stabilizer can be used in place of the standard tenaculum to hold the cervix open during the IUD insertion procedure.

After cesarean deliveries, the IUD is placed in the uterus with forceps or manually during surgery prior to suturing the uterine incision.

[83] He moved to the United States, where his colleagues H. Hall and M. Stone took up his work after his death and created the stainless steel Hall-Stone Ring.

A Japanese doctor named Tenrei Ota also developed a silver or gold IUD called the Precea ring (transl.

[83] These included the infamous Dalkon Shield, whose poor design caused bacterial infection and led to thousands of lawsuits.

The first model, Progestasert, was conceived of by Antonio Scommegna and created by Tapani J. V. Luukkainen, but the device only lasted for one year of use.

[6] A study found that female family planning providers choose LARC methods more often (41.7%) than the general public (12.1%).

[95] Mechanism of actionCopper-releasing IUCsWhen used as a regular or emergency method of contraception, copper-releasing IUCs act primarily to prevent fertilization.

Emergency insertion of a copper IUC is significantly more effective than the use of ECPs, reducing the risk of pregnancy following unprotected intercourse by more than 99%.2,3 This very high level of effectiveness implies that emergency insertion of a copper IUC must prevent some pregnancies after fertilization.Emergency contraceptive pillsTo make an informed choice, women must know that ECPs—like the birth control pill, patch, ring, shot, and implant,76and even like breastfeeding77—prevent pregnancy primarily by delaying or inhibiting ovulation and inhibiting fertilization, but may at times inhibit implantation of a fertilized egg in the endometrium.

Pregnancy begins with implantation according to medical authorities such as the US FDA, the National Institutes of Health79 and the American College of Obstetricians and Gynecologists (ACOG).80Ulipristal acetate (UPA).

Early treatment with ECPs containing only the progestin levonorgestrel has been shown to impair the ovulatory process and luteal function.83–87p.

Several clinical studies have shown that combined ECPs containing ethinyl estradiol and levonorgestrel can inhibit or delay ovulation.107–110How does EC work?In 2002, a judicial review ruled that pregnancy begins at implantation, not fertilisation.8 The possible mechanisms of action should be explained to the patient as some methods may not be acceptable, depending on individual beliefs about the onset of pregnancy and abortion.Copper-bearing intrauterine device (Cu-IUD).

Copper is toxic to the ovum and sperm and thus the copper-bearing intrauterine device (Cu-IUD) is effective immediately after insertion and works primarily by inhibiting fertilisation.9–11 A systematic review on mechanisms of action of IUDs showed that both pre- and postfertilisation effects contribute to efficacy.11If fertilisation has already occurred, it is accepted that there is an anti-implantation effect,12,13Levonorgestrel (LNG).

The precise mode of action of levonorgestrel (LNG) is incompletely understood but it is thought to work primarily by inhibition of ovulation.16,17Ulipristal acetate (UPA).

It is believed that this reaction, a sterile inflammatory response, produces tissue injury of a minor degree but sufficient to be spermicidal.

Very few, if any, sperm reach the ovum in the fallopian tube.The progestin-releasing IUD adds the endometrial action of the progestin to the foreign body reaction.