Abnormal pregnancy outcome rates associated with UCCs in published case series have been reported to range from 38–85%, encompassing fetal chromosome abnormalities, fetal anomalies, and local cord complications[4]. Trisomy 18 and 21 emerged as the most prevalent fetal chromosome abnormalities, while fetal abdominal wall anomalies, patent urachus, and FGR were the predominant combined fetal anomalies. Consequently, comprehensive ultrasound examinations, amniocentesis for chromosome analysis, and genetic counseling are recommended for this specific patient group[5].
Contrary to the assertion in previous literature, which suggests that isolated UCCs with normal karyotype do not significantly increase the risk of adverse pregnancy outcomes[6], our case series challenges this notion. Our observations indicate that adverse events stemming from local complications of persistent UCCs in the second and third trimesters are still a valid concern. The umbilical cord functions as a critical conduit for maternal-fetal material exchange, and disruptions by other umbilical abnormalities, such as vascular abnormalities (eg, umbilical vessels thrombosis and aneurysm) or tumors (eg, angiomyxomas and teratomas), have been reported to associate with adverse events due to insufficient umbilical cord supply[6]. Local cord complications, arising from factors like torsion, umbilical vessel compression, thrombosis, tumor or cyst rupture, vessel tearing, bleeding, and hematoma, can lead to fetal anemia, hydrops, distress, growth restriction, or fetal demise[7].
Despite limited literature elucidating the impact of UCCs on umbilical cord local complications, our cases and existing literature underscore the potential for severe fetal effects. This underscores the need for clinicians to establish a hierarchical management platform for UCCs, selecting appropriate screening strategies for different UCC types and considering intrauterine treatments when necessary.
Previously, the size of the UCC was considered to be an important grading indicator, with Sepulveda et al. suggesting that UCCs exceeding 3 cm may lead to local complications and aspiration of the cyst is indicated if it is very large and causing symptoms[6]. In our research, Cases 6, 8, 9, 10, and 16 experienced complications such as FGR, fetal distress, and fetal demise, and while these could not be attributed to fetal structural malformations or chromosome abnormalities, a potential association with umbilical cord local complications was considered. Notably, these cases shared a commonality: the longest diameter of the UCCs exceeded 5 cm, and the shortest diameter exceeded 2.5 cm. Therefore, the author posits that cysts with a diameter equal to or greater than 3 cm should prompt increased vigilance for complications, suggesting a potential need for more frequent ultrasound monitoring and fetal cardiotocography (CTG), aligning with the perspective of Sepulveda et al.
Although most of the combined fetal deaths in the literature have occurred in larger UCCs, instances of fetal death due to UCCs smaller than 3 cm have been reported. In 2005, Sepulveda et al. documented a case of an allantoic cyst with an umbilical cord hematoma resulting in fetal demise, despite the cyst having a maximum diameter of only 1.6 cm[8]. Similarly, Brown et al. reported pseudocyst rupture with secondary umbilical cord hematoma and fetal death, where the pseudocyst's maximum diameter was less than 3 cm, yet its rupture grossly distended the umbilical cord over half its length at the time of fetal demise[9]. On the other hand, our literature review identified 11 cases of UCCs with a maximum diameter exceeding 10 cm, as shown in Table 2, of which only one case resulted in fetal death. Thus, the importance of UCC size alone appears diminished. The size of UCCs and the length of the involved umbilical cord do not necessarily correlate with an increased likelihood of fetal death. Furthermore, the risk threshold for cyst size may vary by gestational week, complicating the application of cyst size as a grading criterion. It might be more accurate to establish a ratio parameter combining cyst size and fetal biometry to assess risk during pregnancy, akin to the lung-to-head ratio (LHR) in congenital diaphragmatic hernia or the cystic adenomatoid malformation volume ratio (CVR) in congenital cystic adenomatoid malformation.
Table 2
Outcome of UCCs with a maximum diameter exceeding 10 cm.
literature | maximum UCC diameter/cm | perinatal outcome | GA at delivery/ weeks | Mode of Delivery |
Kiran(2003) | 50 | alive | 39 | CS |
Kilicdag(2004) | 50 | alive | 37 | CS |
Jacques(2013) | 20 | IUD | 26 + 4 | VD |
Wilson(1994) | 16 | alive | 36+ | VD(after aspiration) |
Wanyonyi(2023) | 15 | alive | 38 | CS |
Jauniaux(1990) | 2 cysts(13/8) | alive | 37 | CS |
Haino(2010) | 10.6 | alive | 37 | CS |
Zmora(2020) | >10 | alive | Term | unclear |
Draper(2014) | 10 | alive | 36 + 6 | VD |
Angelico(2019) | 10 | alive | 36+ | CS |
Matsuda(2011) | 10 | alive | 39 | unclear |
Rocha(2017) | 10 | alive | 39 | VD(Vaccum-assisted) |
* GA: gestational age; CS: caesarean section; VD: vaginal delivery.
However, as seen in our Case 6, the ultrasound before fetal death demonstrated a dramatic increase in the cyst size, suggesting that suddenly change in the cyst size may be associated with adverse perinatal outcomes. Likewise, Battaglia et al reported an allantoic cyst in which comparison of two ultrasound examinations 12 hours apart revealed an increase in cyst volume and a worsened UA Doppler velocimetry. Subsequent cardiotocographic monitoring showed a bradycardic non-reactive trace with late decelerations, suggesting fetal hypoxemia[10]. Therefore, the authors suggested that fetal monitoring and frequency of ultrasound examinations should be enhanced if ultrasound suggests a suddenly increase in cyst volume.
Doppler ultrasound, a suitable method for detecting compression of umbilical circulation, raises the question of its utility as a predictive factor for fetal demise in UCCs. In our past experience, fetal distress and demise due to umbilical vascular accident tend to occur rapidly and manifest as sudden death. As in our Case 6, fetal death occurred 1 day later despite normal umbilical artery, middle cerebral artery, and ductus venosus blood flow. Again, none of the deaths we reviewed in literature had a Doppler ultrasound change prior to death except the case reported by Battaglia et al. Therefore, we assert that Doppler ultrasound has limited evaluative value for UCCs.
Considering the lack of clear predictors for intrauterine adverse events in UCCs, it is crucial for parents to be informed that, despite close surveillance, the possibility of sudden umbilical vascular accidents cannot be entirely excluded.
If UCCs are very large, increased rapidly, or causing symptoms, intrauterine therapy may be a viable option to offer to patients who are extremely concerned about an adverse event, before the fetus is viable. Previously reported few intrauterine treatments for UCC were limited to ultrasound-guided cystic fluid aspiration, with the objective to reduce cyst size. However, the limitations of this approach are evident, as cystic fluid regeneration may nullify the effects of aspiration. Wilson performed aspiration of a 16 cm UCC at 36 weeks' gestation, which decreased the volume by one half after 350 ml was withdrawn, but the cyst increased to three fourths the previous largest volume on the following day[11]. Similarly, Edgardo managed a large pseudocyst associated with an angiomyxoma with two percutaneous sonographically-guided aspirations of 400 mL of fluid at 27 and 32 weeks, but the cyst fluid also reaccumulated[6]. Interestingly, Lisovaja et al reported a case of pseudocyst combined with umbilical cord angiomyxoma, which spontaneous ruptured at 34 weeks of gestation without hemorrhage, after which an increase in the fetal abdominal circumference of the fetus was observed, suggesting rupture and decrease in size of the cyst can promote umbilical vessels flow and improve fetal growth[12]. The notion of ultrasound-guided UCCs ostomy, facilitating continuous drainage of cystic fluid, has been inspired by Lisovaja`s report. The feasibility and efficacy of such an intervention warrant further consideration.
The mode and gestational week of delivery for UCCs lack consensus in the literature. While many large UCCs have been successfully carried to term, a considerable majority of these cases opted for caesarean section deliveries. The concern among obstetricians regarding the risk of rupture during vaginal delivery for large UCCs underscores the lack of a standardized approach. However, there is only one report of an antenatal cystic fluid aspiration that resulted in a successful vaginal delivery[11]. The contentious debate revolves around whether antenatal ultrasound-guided cyst aspiration should be considered for women with a strong preference for vaginal delivery.