The incidence of Bandl’s ring and its impact on labor outcomes: a review of the published literature

Main findings

To the best of our knowledge, this is the first scientific paper to examine the outcomes of published cases involving Bandl’s ring. Our findings indicate that reports of Bandl’s ring in the medical literature are rare, despite its association with adverse maternal and perinatal outcomes. This underreporting is likely due to the difficulty in making a clinical diagnosis. The abnormal indentation of the maternal abdomen is subtle and often goes unnoticed, and delayed recognition can result in serious complications for both mother and child. Although current available data do not permit a comparison of outcomes based on whether the diagnosis was made clinically or via ultrasound, the latter method shows potential for enabling earlier and more accurate identification of abnormal uterine ring (Table 4).

Hystorical background

In 1872, German anatomist Christian Wilhelm Braune, a pioneer in the use of frozen cadavers for anatomical studies, documented a circular constriction ring dividing the uterus into upper and lower segments in a full-term pregnant woman who died during the second stage of labor [14].

Three years later, in 1875, Austrian obstetrician Ludwig Bandl expanded on Braune’s findings by identifying a similar constriction ring in a living patient. Like Braune, he located the ring at the junction between the upper and lower uterine segments and proposed that the lower segment originated entirely from the cervix.

Bandl argued that if Braune’s findings were accurate, then substantial anatomical and functional changes in the cervix must occur weeks or even months before labor begins. He questioned whether the cervical canal and internal os could transform into the structure Braune described within just a few hours [15].

Luis Rudolph, after reviewing 350 literature cases and 21 personal clinical cases, highlighted the underrecognized clinical importance of intrauterine constriction rings in obstructed labor. He described the condition as primarily functional in nature and noted that it has been referred to by at least 20 different names. He challenged the idea that all such rings correspond to Schroeder’s contraction ring or the retraction rings described by Barbour and Lusk, citing the diverse anatomical locations of these rings. The classification of the condition under the term “constriction ring dystocia” is mostly based on biological assumptions [16].

Rudolph further differentiated between physiological and pathological retraction rings. The physiological type, forming as part of the normal transition between uterine segments, is best referred to as the “physiological retraction ring” and should not be confused with Bandl’s ring, which originates from Braune’s postmortem discovery and is linked to mechanical dystocia. The pathological retraction ring, on the other hand, develops due to mechanical dystocia and represents an intensified form of the physiological ring, resembling Bandl’s original description. This terminology emphasizes the dysfunction caused by mechanical obstruction, especially in pregnancies involving younger or older mothers. Moreover, constriction rings are defined as localized circular uterine contractions that can appear at any level of the uterus and may lead to dystocia even when fetal position and pelvic dimensions are normal [16].

Good noted variation in the terminology used in literature, including terms such as “retraction ring”, “physiological ring”, “normal retraction ring”, “contraction ring”, and “normal contraction ring.” When the condition is considered pathological, it has been labeled as “pathological retraction ring”, “Bandl’s ring”, “pathological contraction ring”, or simply “constriction ring” [17].

Brody echoed the inconsistency in naming, listing terms like “Bandl’s ring”, “contraction of Bandl’s ring”, “White’s contraction ring dystocia”, “Pride’s retraction ring dystocia”, “simple contraction/retraction ring”, and “Rudolph’s uterine constriction ring” [18].

Gilliatt observed a wide range of terminology as well. In the UK, the term “contraction ring” is commonly used. In contrast, continental Europe lacks a standardized term, while in the United States, “retraction ring” or “Bandl ring contraction” are more frequently used. De Lee used “stricture uteri” to describe similar conditions, while Schroeder referred to a ring that forms during normal, uncomplicated labor as a “contraction ring” [19].

Animal studies have shown that some species are predisposed to develop constrictive rings or zones capable of transverse contraction [20], 21].

Greenhill emphasized the importance of distinguishing the constriction ring that complicates labor from both physiological and pathological retraction rings described by Rudolph and Ivy. The physiological retraction ring – also known as Schroeder’s contraction ring, Barbour and Lusk’s retraction ring, or Bandl’s physiological ring – is situated between the upper and lower uterine segments and typically appears only in neglected or obstructed labor, often during the second stage [22], [23], [24].

Allen defined a constriction or contraction ring as a localized tightening of circular muscle fibers, which can occur at any stage of labor but is most commonly seen in the second stage. If it appears during the third stage, it is often called an “hourglass contraction ring.” This type may be associated with the use of ergot alkaloids or pituitary extracts, which can cause excessive uterine contractions, leading to placenta entrapment and the formation of an hourglass-shaped uterus [23].

Mulcay, summarizing the work of various authors, noted that most cases occurred in first-time mothers [primigravidae+], with 60–70 % presenting in a posterior occipital position [24].

In 1955, Lauge-Hansen used advanced radiographic imaging (roentgenography) to demonstrate that Bandl’s ring or a spastic contraction ring could potentially be diagnosed early in labor. These imaging techniques were valuable for both diagnosis and monitoring labor progression [25].

Strength and limitation

The primary strengths of this systematic review lie in its comprehensive literature search and the detailed evaluation of Bandl’s ring. Nevertheless, the study has several limitations, including the retrospective nature of the included studies, their small sample sizes, and the absence of stratified analysis. Additional limitations involve heterogeneity in the diagnostic and management approaches across the studies and the impossibility to exclude other confounding factors that may impact on fetal and maternal outcome. Moreover, the limited number of cases in which ultrasound was performed prevented a robust assessment of the technique’s diagnostic accuracy. On this basis it is still impossible provide any useful guide to obstetricians managing these cases (Figure 1).

Figure 1:

Ultrasound appearance of the Bandle’s ring around fetal neck (arrow) and anatomic drawing of a longitudinal section of the uterine with the ring.

Implication for clinical practice

Ultrasound has become an increasingly accepted diagnostic tool in labor wards, providing a non-invasive and reliable means of monitoring labor progression [26]. Its utility has also been proposed in the context of prolonged labor. Emerging evidence suggests that ultrasound can aid in the early detection of Bandl’s ring, allowing for prompt intervention and potentially improving outcomes for both mother and child. On this basis we can suggest that in presence of an arrested second stage of labor a transabdominal ultrasound should be performed looking at the fetal occiput position and the characteristics of the anterior uterine wall (Figure 2). In this condition stopping oxytocin infusion if present, using acute tocolysis or administering nytroglicerin at the time of fetal extraction should be considered despite no evidences still exist on their efficacy. Similarly there is no agreement on the type of incision. A vertical midline incision through the ring itself has been suggested to provides access to upper and lower uterine segments [27]. However there are no comparative studies on the advantages of this approach compared to a trasverse incision on the retraction ring in term of surgical challenges and rate of complications.

Figure 2:

Suggested flow chart to diagnosis uterine Bandle’s ring in women with arrested second stage of labor.

These findings highlight the need for further prospective studies to investigate the role of ultrasound in diagnosing obstructed labor and preventing related complications.