Adhesions are the most common cause of SBIO in pregnant women [6]. The most frequent causes of postoperative adhesions in the general population are appendectomies and gynaecologic procedures [11].

Even without prior abdominal surgeries, adhesions cannot be ruled out as the underlying cause of SBIO, as 11% of adhesions are congenital [11].

The second most common cause of SBIO in our review was internal herniation (28.8%), mainly in patients with previous RYGB. This bariatric procedure, as a treatment for severe obesity, has increased in the past decade; most patients are women [12]. While the weight loss experienced by patients who undergo RYGB helps to reduce health risks, these patients are at risk of bariatric surgical complications, such as internal herniation, intussusception, and small bowel obstruction during pregnancy, due to the increase in intra-abdominal pressure caused by the gravid uterus and the reduction in excessive fat [13]. The American College of Obstetricians and Gynecologists (ACOG) published a review and practice bulletin in 2009 to inform obstetricians about SBIO in pregnant women as a well-recognized life-threatening late complication of RYGB [14]. Some authors have suggested that a bariatric surgeon should evaluate any pregnant patient with RYGB and abdominal complaints [15]. Some centres advocate a low threshold for diagnostic laparoscopy to rule out internal herniation. Internal hernias post-RYGB usually occur at 3 locations: (1) between the Roux limb mesentery and transverse mesentery (Petersen’s space); (2) at the defect in the transverse mesocolon; and (3) at the jejunojejunostomy mesenteric defect. All potential defects causing internal herniation must be inspected and closed during surgical exploration to prevent recurrence.

Abdominal pain is present in more than 85% of pregnant women with SBIO [16]. Due to the nature of pregnancy, abdominal pain can be confused with gastroenteritis or premature labour, whereas vomiting might be treated as hyperemesis gravidarum. Constant and nonremitting abdominal pain should alert practitioners to rule out the possibility of intestinal obstruction, particularly closed-loop obstructions, as the abdominal pain caused by gastroenteritis or uterine contractions is usually associated with periods of remission. Nausea and vomiting persisting into or starting in the third trimester should warrant further investigations to rule out intestinal obstruction.

Physical examination in pregnant women can be challenging and nonspecific due to the gravid uterus. The enlarged gravid uterus might mask abdominal distension caused by SBIO. Intermittent colicky pain caused by the obstructed bowel might be misinterpreted as labour pain. As the obstruction progresses, the uterus may contract due to the underlying irritation. This might confuse obstetricians, who incorrectly diagnose SBIO as early labour with contraction pain. Other clinical signs, such as fever, tachypnoea, hypotension, and tachycardia, usually appear later as secondary manifestations of severe acidosis and infection. Unfortunately, at this stage, this usually means that the bowel is compromised, and it might be too late to offer surgical intervention [17]. All these challenges highlight the clinical difficulties in diagnosing SBIO in pregnant women.

Laboratory tests yield little information besides electrolyte imbalances and impaired renal function in dehydrated patients. Leucocytosis is common during pregnancy, especially in late pregnancy and during labour. However, an increasing trend of leucocytosis over several hours is significant in gravid patients with suspected obstruction and should alert obstetricians to consider other causes [16].

Radiological imaging, such as X-rays of the abdomen, is used to aid in diagnosing SBIO. Diagnosis may be delayed due to apprehension about using X-ray imaging and exposing the foetus to radiation. However, significant maternal and foetal mortalities associated with acute abdominal emergencies outweigh the potential risk of radiation exposure to the foetus [10]. Sometimes, in the early stage of obstruction, a single film might not be sufficient to diagnose SBIO [18]. However, progressive bowel dilatation or air-fluid levels in serial films obtained at 4–6 h intervals are indicative of SBIO [19]. Previous literature described using contrast studies such as gastrografin or barium studies to diagnose SBIO [17]. This has been gradually phased out in recent years, especially with the widespread availability of advanced imaging modalities such as CT and MRI scans.

The use of ultrasound is widespread, as this modality does not confer any radiation exposure to the foetus. However, one study reported that only 55% of patients had ultrasound findings similar to the surgical findings [20]. Thus, ultrasound is not the most sensitive modality to rule out SBIO in pregnant patients.

CT scans play a role as a diagnostic modality in the general population. Abdominal CT scan with oral and intravenous contrast is the best radiological tool to evaluate patients with previous RYGB who present with obstructive symptoms suggestive of internal hernias [21]. Unfortunately, radiation exposure to the foetus is highest when a full scan of the abdomen and pelvis is performed [22]. Hence, the benefits of a CT scan should be weighed against the cumulative radiation exposure to the foetus. These levels vary by institution; practitioners should be aware of the cumulative radiation exposure to the foetus. MRI has been gaining popularity in pregnant women to diagnose intestinal obstruction and the underlying cause, as this modality provides excellent soft tissue multiplanar imaging without ionizing radiation [23]. The use of gadolinium remains contraindicated as this agent crosses the placenta, and the effects on the foetus are not fully understood. With the increasing use of MRI and CT scans, early diagnosis of SBIO in pregnant women is possible, especially in regions where health care resources are more accessible.

With an earlier diagnosis, health care practitioners can intervene early to reduce maternal and foetal morbidity and mortality. In this review, most patients (61%) underwent surgery in the first 24 h after presentation. Due to the higher stakes in pregnant patients, past literature strongly recommended operative intervention for intestinal obstruction in pregnant women [17]. As early as 1932, Murray Blair suggested that the abdomen should be opened, and the cause should be ascertained when intestinal obstruction occurs during a normal intrauterine pregnancy [24]. Harper WB Jr states that conservative treatment for intestinal obstruction during pregnancy is generally not recommended because of the frequency of closed-loop obstruction, which occurs in up to 40% of patients [25]. Perdue et al. reported a significant risk in treating SBIO during pregnancy with tube decompression alone, except possibly in pregnant patients with sigmoid volvulus [6].

Pregnant women with RYGB-associated SBIO generally require surgical exploration for diagnosis and treatment, even if the condition responds to conservative treatment measures [26]. This is because the common causes of SBIO post-RYGB, such as adhesions, mesenteric defects, and stenosis, persist without surgical intervention, potentially leaving the patient at risk for recurrent and catastrophic SBIO. Gudbrand et al. described a case of recurrent SBIO caused by internal herniation in a pregnant woman with previous RYGB despite the closure of Petersen’s defect in the first surgery performed laparoscopically. She eventually underwent laparotomy and closure of the Petersen defect when the condition recurred within 8 weeks [9]. In this review, all patients with SBIO and a history of previous RYGB were operated on. All mothers and babies survived except in four cases, including two cases of foetal mortality, one case of maternal mortality, and one case in which both the mother and baby did not survive due to a delay in diagnosis.

Surgical management and techniques in this group of patients do not differ from those in the general population. Once the decision for surgery is made, the consideration of which surgical approach to utilize (laparoscopy versus laparotomy) is based on the surgeon’s skills and the availability of the appropriate staff and equipment. With the increasing popularity of minimally invasive surgery (MIS), there are concerns about the use of MIS in pregnant patients due to the risk to the foetus from trocar insertion and CO2 insufflation, the risk to the mother from pneumoperitoneum causing a reduced venous return to the heart and the ability to obtain adequate view with a gravid uterus. It has been shown that laparoscopy can be performed safely during any trimester of pregnancy with minimal morbidity to the foetus and mother [23]. Nezhat FR et al. reported favourable outcomes in 51 cases of abdominal operative laparoscopy performed in pregnant patients [27]. In our review, 15.9% of patients underwent successful MIS. Most patients still undergo laparotomy, especially if the case is complicated or the diagnosis is uncertain.

Management of the foetus at the time of operation will depend on the gestational age of the foetus as well as the maternal condition at the time of laparotomy. Unless the pregnancy is at term and the foetus is ready to be delivered, surgeons should minimize manipulation of the uterus as much as possible. Hypotension and hypoxia, while the mother is anaesthetized, are the two most common causes of foetal death or abortion [28]. In this review, only 21% of foetuses were delivered during surgery. If foetal delivery is needed during the operation, this should precede relief of the obstruction.

Conservative management of SBIO in pregnant women was frowned upon, as later intervention often leads to dire consequences. Chiedozi LC et al. reported a case where a pregnant woman with SBIO was started on a trial of conservative treatment [29]. Ten days later, the patient experienced maternal collapse from shock. She was resuscitated and brought to the operating theatre immediately. Most of the intestine was found in a tight volvulus at laparotomy. Eight feet of the gangrenous small intestine were resected, but both the patient and foetus died 12 h after the operation. This case highlights the importance of carefully selecting patients for a trial of conservative treatment, especially if no prior imaging has been done to rule out life-threatening emergencies such as closed-loop obstruction or volvulus.

If closed-loop obstruction and bowel ischaemia have been ruled out and the patient has no prior history of RYGB, stable patients with reassuring foetal tracing can be started on a trial of conservative management. Most of this carefully selected group of patients have SBIO due to adhesions with no worrisome findings on CT or MRI. M Phillips et al. described a case of recurrent SBIO secondary to adhesions in a pregnant woman. She was placed on conservative management for 10 weeks with an elemental diet via tube feeding. She delivered a healthy baby boy via elective caesarean section due to breech presentation without any complications [30].

SBIO can cause malnutrition in pregnant women due to the failure to absorb nutrients from the gut. This will increase the risk of spontaneous abortion, congenital malformations, intrauterine growth restriction (IUGR), preterm delivery, and perinatal mortality and morbidity [31]. For the past decades, the use of TPN was described as providing adequate nutritional support for malnourished pregnant women. Caruso et al. demonstrated that intravenous nutrition is well tolerated and can be administered safely and effectively to malnourished pregnant women without catheter-related or metabolic complications [32]. After appropriate counselling, patients who require TPN during conservative management for SBIO should be referred to experienced obstetric centres where TPN and careful monitoring of the maternal and foetal conditions can be carried out. In an unfortunate case, Lee S et al. reported a case where the patient presented with SBIO secondary to adhesions in the second trimester [33]. The patient was started on TPN and observed closely for 18 days. Unfortunately, the foetus developed acute onset foetal brain haemorrhage, likely secondary to vitamin K deficiency, and thus surgical intervention had to be offered. The baby died shortly after delivery via caesarean section in the same setting. This highlights the need for close observation of both maternal and foetal conditions. Due to the high costs of TPN and limited availability, especially in areas with limited access to health care resources, TPN initiation in pregnant patients with SBIO who are treated conservatively can be difficult.

Over the years, there has been an increase in the survival of pregnant patients with SBIO. A 75% maternal fatality rate was reported in Ludwig’s series in 1913 [5]. Subsequently, Harper WB Jr reported a maternal mortality rate of 22% from 1928 to 58, [25], and Morris reported a maternal mortality rate of 12% in 1965 [16]. Immediate causes of maternal death include irreversible shock and infection. The overall maternal mortality rate in our series was 3.7%. This improvement is likely due to early diagnosis and early intervention.

Compared to the maternal mortality rate, the foetal mortality rate is usually higher. Perdue et al. reported a foetal mortality rate of 26% compared to a maternal mortality rate of 6% in his case series. In our series, the foetal mortality is 16%, which is lower than what was reported by Perdue et al. in 1992. This is a reflect of medical improvement over the years, where early diagnosis and intervention can be carried out promptly.

As the mother’s condition deteriorates, the foetal condition will worsen rapidly. There was a dramatic progression of foetal mortality as patients approached the third trimester, with 15 foetal deaths occurring in the third trimester group. It is tragic for patients to lose their viable babies due to abdominal conditions. In our review, there were 5 cases of maternal and foetal mortality. Four out of the 5 patients were operated on immediately upon presentation. Despite immediate surgical intervention, the damage caused by profound shock was irreversible, resulting in the demise of the patients and the foetuses. One can only hope that pregnant patients have better access to health care and thus present earlier when they are ill.