Finley et al. suggested that a delayed return of foetal bowel from the umbilical cord to the foetal abdomen, potentially resulting in the failure of normal fixation of the small bowel mesentery, could predispose to intrauterine volvulus, as observed in their reported case [15]. Due to the lesser or greater degree of rotation of the gut around the superior mesenteric artery, Cloutier et al. blamed the absence of broad mesenteric attachment [9]. While the majority of postnatal volvulus cases were attributed to malrotation, it is noteworthy that only 17% of intrauterine volvulus cases were associated with malrotation. Additionally, a significant proportion of intrauterine volvulus cases (46%) were found to have no identifiable aetiological or associated anomalies.

Our review identified 22 cases (29%) that were associated with atresia. Notably, the literature cites the rate of atresia in volvulus cases as 25% [5, 38]. However, it remains unclear from the reports whether these atresias occurred secondary to the volvulus or if the volvuli occurred secondary to the atresia. We posit that both scenarios may be true [1, 58].

In the literature, the prenatal ultrasonographic findings of intrauterine volvulus were reported as polyhydramnios, dilated intestinal loops, static abdominal mass, ascites, peritoneal calcifications and increased abdominal circumference [2,3,4, 17, 26, 30, 32, 36, 38, 40, 41, 46, 51]. In our review, we identified similar lists of prenatal USG findings, although peritoneal calcifications were less frequent while meconium cysts/pseudocysts were more common. Additionally, the literature reported foetal biophysical profile findings as foetal distress with decreased foetal movements and decreased variability during foetal monitorisation, along with foetal cardiac sinus rhythm with anaemia and increased peak systolic velocity in the middle cerebral artery Doppler [2,3,4, 17, 26, 30, 32, 36, 38, 40, 41, 46, 52] which was mostly observed after 27 weeks of gestation [4, 25, 26, 41]. We found similar foetal biophysical profile findings and more frequent foetal bradycardia, which also increases mortality.

The ultrasonographic signs of intrauterine volvulus can be indicative of several differential diagnoses, including intestinal atresia, meconium ileus, meconium peritonitis, segmental small bowel dilatations, cystic mass lesions such as mesenteric cysts, lymphangioma, or teratoma, Meckel’s diverticulum, duplication cysts, and omphalomesenteric cysts [45, 51, 53]. Definitive diagnosis of volvulus could only be made by the presence of the “whirlpool or snail configuration” or the “coffee bean sign” [1, 3, 4, 26, 32, 36, 38, 40, 43, 49, 53], which are difficult to define [5, 30] and not always associated with volvulus [59]. The sensitivity and specificity of the whirlpool sign were reported as 89% and 92%, respectively in neonatal volvulus cases [54, 60]. We found that the “whirlpool or snail configuration” was reported in 19 cases (24%) and the “coffee bean sign” was reported in 4 cases (5%). Due to the decreased occurrence of specific signs of volvulus and the increased prevalence of nonspecific signs that share many potential differential diagnoses, diagnosing and effectively treating these cases in a timely manner becomes challenging. Consequently, this contributes to elevated mortality and morbidity rates [3,4,5,6, 9, 13, 25, 30, 41, 43, 49, 51, 52].

Half of all the cases showed findings of foetal distress. Bartholmot et al. reported that 61.5% of mothers applied with the complaint of decreased foetal movements [1]. The increased risk of foetal loss and foetal distress may occur because of (1) Elevated intraabdominal pressure due to distended bowel and ascites, if present, can impede umbilical venous return and subsequently reduce cardiac output; (2) anaemia resulting from hemoperitoneum can lead to diminished perfusion; (3) the release of toxins from gangrenous or necrotic bowel tissue can exacerbate the physiological stress on the foetus [12, 22]; and (4) fluid escape into the third cavity (dilated bowel lumen) leading to hypovolemic shock and cardiovascular failure [33]. Leung et al. observed that following intrauterine paracentesis of ascites induced by meconium peritonitis, there was an improvement in foetal movements and suboptimal foetal heart rate patterns on non-stress test (NST). This improvement was attributed to the removal of irritant meconium, alleviation of compression on the foetal thorax, and potentially reducing compression on the vena cava, leading to enhanced venous return [24].

The literature mentioned that the outcome of intrauterine volvulus depends on the length of the viable intestine, level of obstruction, presence of meconium peritonitis, associated anomalies, birth weight, and gestational age at birth [17, 30, 38, 49, 54]. We found that the presence of foetal bradycardia at prenatal visits, and presence of meconium cyst or pseudocyst reported in operation were significantly related to decreased survival. Notably, 11 cases (17%) had short bowel syndrome, and two of them died.

One of the factors influencing mortality was the presence of meconium cyst/pseudocyst during operation. In deceased patients, a lower occurrence of dilated bowel in prenatal ultrasonography (44% vs 75%) and a higher incidence of meconium cyst/pseudocyst during operation (36% vs 9%) were observed. Thus, we hypothesize that mortality rises with necrosis and progression of volvulus to perforation, resulting in reduced bowel diameter and formation of meconium cysts.

Foetal anaemia, recognised for increasing mortality and morbidity in both the foetus and newborn, was more prevalent in cases with intrauterine volvulus [13, 36, 38, 42, 43]. While approximately one fourth of intrauterine volvulus cases in the literature were associated with foetal anaemia, we were unable to demonstrate its impact on mortality in our review. However, we observed that hemoperitoneum was a contributing factor to foetal anaemia. In line with the guidance provided by Kornacki et al., we advocate for evaluating the hemodynamic status of the foetus by measuring the peak systolic velocity of the middle cerebral artery in cases presenting with foetal bowel pathology, particularly in foetuses with intrauterine volvulus [36].

In severe cases, volvulus can manifest early in pregnancy, leading to the development of intestinal atresia and meconium peritonitis. Such instances may necessitate immediate intervention or preterm delivery due to the presence of foetal distress [6, 18]. Additionally, severe intrauterine volvulus led to ischaemic necrosis of intestines and might activate both feto-placental and hypothalamic release of stress hormones that results in uterine contractions and preterm labour [3, 20, 28, 30, 32, 42, 55]. We found that in the deceased patients, the preterm labour was more frequent (54% vs 21%), while urgent caesarean section and preterm newborn ratio was less frequent (27% vs 47%, 58% vs 78%, respectively). Therefore, we deduced that in cases where survival was achieved, obstetricians closely monitored these patients to detect signs of foetal distress and promptly conducted urgent caesarean sections to prevent foetal demise.

Two studies highlight that delays in diagnosing and treating intrauterine volvulus can lead to high complication rates, including loss of intestinal segments and the development of short bowel syndrome [17, 18]. Some authors suggest that delivery can be promptly performed via caesarean section after 34 weeks of gestation, while the timing of delivery before 34 weeks depends on the severity of the foetal condition and the need for prophylactic measures for foetal lung maturation [43, 45], Additionally, in cases where prenatal diagnosis is established, some authors recommend preterm delivery and emergent surgical intervention [26, 42]. However, others emphasize that the timing of delivery should be based on obstetrical indications, given the uncertainty in differentiating between intestinal atresia, meconium ileus, and volvulus [14, 17]. It’s also suggested to closely monitor foetuses presenting with signs of bowel obstruction and to consider urgent caesarean section in the presence of acute abdominal pathology or non-reassuring foetal status [1, 21, 55] when findings of acute abdominal pathology such as the heterogeneous echogenicity within the dilated bowel or the disappearance of peristalsis are presented [21] or when there are findings of non-reassuring foetal status [52, 55]. For instance, Herrera et al. recommend urgent delivery in the presence of specific indicators such as ascites, absence of intestinal peristalsis, decreased foetal movements, or sudden changes in bowel diameter [51], while Alvarez et al. suggest delivery when findings of thoracic compression are detected [14]. We recommend closely monitoring foetuses exhibiting signs of intestinal obstruction and administering betamethasone therapy for pulmonary maturity, particularly given the observed frequency of preterm labour. Urgent caesarean section should be considered as an option before foetal biophysical profile findings deteriorate further. It’s important to note that planned preterm delivery solely based on ultrasound findings is not advised, as these findings may also be indicative of conditions such as atresia or meconium peritonitis that do not necessitate urgent intervention. However, the likelihood of preterm delivery may still be higher due to a greater incidence of non-reassuring foetal tests.

However, our study has several limitations. Firstly, we were unable to access all the available case reports and