Is contraceptive failure more likely with a malpositioned IUD/IUS?

Anteby et al.3 reported on transvaginal sonographic (TVS) assessment of 25 pregnant women with an IUD and 100 non-pregnant women who had had an IUD fitted 45–60 days previously. The control women had Multiload 375^© devices, and it is implied but not specifically stated that the case women had these devices also. The IUD was found to be displaced to the cervix in 13/25 (52%) of the pregnant women and 7/97 (7%) of the non-pregnant women. The authors concluded that failure may be due to a malpositioned device and recommended replacing an IUD that is incidentally found to be low-lying.

A retrospective case-control study of 216 pregnant women with an IUD and 657 non-pregnant women with an IUD was described by Thonneau et al.5 Risk of failure was associated with lower age of the woman and lower copper content of the IUD. There was no effect of polyps, fibroids or medication, but previous IUD expulsion was a risk factor for failure, odds ratio (OR) 3.31 [95% confidence interval (CI) 1.4–7.8]. Thonneau et al.6 also published a review article in 2001 that looked at risk factors for IUD failure. They commented that displacement of the IUD reduces effectiveness but this was based solely on the data from the Anteby et al. paper.3

Moschos and Twickler7 published a retrospectively derived case series of 42 women with IUDs in early pregnancy, and included a TVS-derived description of position of the IUD. Thirty-one (74%) of the pregnancies were intrauterine, three (7%) were ectopic and eight (19%) were diagnosed as pregnancies of unknown location. Of the 31 intrauterine pregnancies, 8/31 of the IUDs were normally positioned, 17/31 were ‘low-lying’ and 6/31 could not be seen.

A retrospective case-control study was published by Braaten et al.8 looking at 182 women with malpositioned IUDs and 182 women with correctly situated IUDs, as determined by TVS. All ultrasound reports from a 5.5-year period at one centre that referred to an IUD were searched and 1748 reports with IUDs in situ were identified. Of these, 10.4% were found to have a malpositioned IUD, the majority of which were in the lower uterine segment or cervix (73%). Embedded or rotated IUDs were also classified as malpositioned, as were expelled or extrauterine devices, which made up 14% of the total. The 182 controls were patients with normally sited IUDs and each was the next consecutive patient in the database after a study case. The main aim of this study was to determine whether malpositioning was more common after postpartum insertion, and the authors reported no statistically significant difference. Of the 182 women with a malpositioned device, 121 had the device removed, but only 30% then took up another highly effective method of contraceptive. Two years later there were more pregnancies in the case group who had had their IUD removed around the time of diagnosis than in the control (normally sited IUD) group whose IUDs were removed electively (19.2% vs 10.5%). No pregnancies were reported in the 28 women who had their malpositioned IUD left in situ.

Finally, Pakarinen and Luukkainen9 described a randomised trial of an intracervical device releasing 20 µg LNG/day. Some 151 women had the device placed intracervically and 147 had the device placed at the uterine fundus. Failure rates, continuation rates and removals for bleeding issues were no different between the two groups. However, expulsion rates were high. This study is suggestive that LNG-releasing devices are likely to have contraceptive efficacy even if they are not placed fundally within the uterus.

Are women with a malpositioned IUD/IUS more likely to experience symptoms of pain and/or bleeding?

Benacerraf et al.10 wished to determine whether abnormally placed IUDs were associated with a higher incidence of pain and/or bleeding than normally placed IUDs. They looked retrospectively at the case records of 167 women with an IUD who had had three-dimensional (3D) TVSs, which were performed for a variety of clinical indications. Twenty-eight (16.7%) of the IUDs were abnormally placed within the uterus, either low-lying or within the cervix, or with abnormally lying side arms. Of these 28 women, 21 (75%) complained of pelvic pain and/or abnormal bleeding. However, statistically significantly fewer women with a normally sited IUD [38/139 (34%)] complained of pelvic pain and/or abnormal bleeding. Twenty-one of the abnormally sited IUDs in women with symptoms were removed and 20 of these women reported an improvement of their symptoms. This study was retrospective and there are no data on the progress of the symptoms of women with normally placed IUDs. However, it does demonstrate the use of 3D ultrasound to improve detection of abnormally placed IUDs, which may be an additional tool in the investigation of women with pain or bleeding.

However, Faundes et al.11 published a case-control study of 236 women with an IUD who complained of bleeding and/or pain, and 245 women who had an IUD but no symptoms. In contrast to Benacerraf et al.'s findings,10 they found no difference in the uterine position of the IUD between the two groups, concluding that a low-lying IUD was not more likely to cause symptoms of pain or bleeding.

De Groot et al.12 published a case report of four women who complained of pain, abnormal discharge and/or dyspareunia with the LNG IUS. Two of the devices were found at hysteroscopy to have perforated the uterine wall and one was lying transversely within the cavity. They recommended consideration for hysteroscopy to determine the cause of symptoms and possible correction of the IUD position.

Can an IUD/IUS move within the uterine cavity?

Faundes et al.13 published a study in 2000 in which they monitored by TVS the position of T-shaped IUDs within the uterus for 90 days following insertion. Two hundred and fourteen women underwent TVS on Days 1, 30 and 90 following copper IUD insertion. Seventeen IUDs were classified as malpositioned at insertion, but 15 of those migrated upwards towards the fundus during the next 90 days. However, at 90 days post-insertion, 21 IUDs were classified as malpositioned, only six of which had been malpositioned at insertion. The authors concluded that the T-shaped IUD does accommodate its position within the uterine cavity and can move both upwards and downwards.

Similarly, Morales-Rosello et al.14 performed TVS monitoring at 2 months post-insertion on a group of 32 women whose IUD was noted to be low-lying immediately after insertion. They found that 97% of the IUDs moved upwards towards the fundus over 2 months. They also concluded that there is movement of IUDs within the uterus in the first few months after insertion.

Faundes et al.15 analysed data on TVS measurements of IUD placement within the uterus from the group of 481 women on which they had previously published. They demonstrated a correlation between endometrial thickness and IUD-myometrium distance and concluded that an IUD can move vertically within the uterine cavity with endometrial thickness changes during the menstrual cycle.

De Kroon et al.16 performed a prospective comparative study in which TVS was used to determine the position of the IUD immediately after insertion and at 6-week follow up. A total of 195 women were included initially with 181 available for follow up. After IUD insertion, the clinician was asked if they felt the IUD was correctly sited. Of 175 IUDs felt to be positioned correctly, 172 were within 5 mm of the fundus on TVS [negative predictive value (NPV) of clinical evaluation 0.98, 95% CI 0.96–1.00]. Of 20 IUDs felt to be incorrectly positioned, 12 were low-lying on TVS [positive predictive value (PPV) 0.6, 95% CI 0.39–0.81]. At follow-up, women were interviewed and examined and clinicians again asked if they felt the IUD was correctly sited. NPV was 1.0 (n=160) and PPV was 0.54, 95% CI 0.26–0.81. Of seven incorrectly sited IUDs that were left in situ, five had migrated to a correct position by the 6-week follow up.

As an alternative to replacing the incidentally found low-lying IUD, Ber et al.17 reported on a case series of 18 patients who were asymptomatic but found to have a low-lying LNG-IUS. Alligator forceps were used to grasp the device in the cervical canal and push it up towards the fundus. This was confirmed to be successful on TVS in 17/18 cases, but 3/17 had become malpositioned again 2 months later. The authors suggest consideration of this technique as a cheaper option to removing and replacing a low-lying LNG IUS.

Is postpartum insertion associated with increased malpositioning of an IUD/IUS?

The systematic review found just one study that directly looked at postpartum insertion as a risk factor for IUD malpositioning. Braaten et al.8 performed a retrospective case control study with a group of women with normally situated IUDs and a group of women in whom the IUD was malpositioned. Malpositioning was not specifically associated with insertion at 6–9 weeks postpartum (OR 1.46, 95% CI 0.81–2.63).