The impact of different sides of the absent umbilical artery on fetal growth in an isolated single umbilical artery

Risk of adverse pregnancy outcome in isolated single umbilical artery diagnosed at the mid-trimester anomaly scan: a large Danish retrospective cohort study

OBJECTIVE

To examine the association of isolated single umbilical artery (iSUA) confirmed at the mid-trimester anomaly scan and adverse pregnancy outcome and congenital malformations with up to 10 years postnatal follow up.

METHODS

This retrospective cohort study included 116,501 singleton pregnancies consecutively enrolled in first trimester screening for aneuploidies and mid-trimester anomaly scan at three University Hospitals in the Capital Region of Copenhagen, Denmark.Data from the Danish Fetal Medicine Database (2008-2017) were verified by manually scrutinizing pre- and postnatal records. The main outcomes of interest were intrauterine fetal demise (IUFD), small for gestational age (SGA), preterm delivery, cesarean section and unrecognized pre- and postnatal congenital malformations.

RESULTS

In total, 775 pregnancies with iSUA were identified. Isolated SUA were associated with a significantly increased risk of IUFD (OR 4.16, 95% CI 2.06-8.44), SGA < 3^rd centile (aOR 2.41, 95% 1.85-3.14) and SGA < 10^th centile (aOR 1.84, 95% CI 1.53-2.21), but not with preterm delivery or cesarean section. The laterality of the missing artery was not associated with SGA. In total, 4.3% of pregnancies with iSUA had unrecognized congenital malformations. 1.5% with iSUA had congenital cardiovascular malformations, which were considered minor.

CONCLUSION

Isolated SUA is associated with IUFD and SGA, supporting surveillance during third trimester. If, during the mid-trimester scan, the sonographer achieves thorough, extended cardiac views and finds no additional malformation other than SUA, fetal echocardiography seems not to be needed.

Changes in Artery Diameters and Fetal Growth in Cases of Isolated Single Umbilical Artery

Background-There are conflicting data in the international literature on the risks of abnormal fetal growth in fetuses presenting an isolated single umbilical artery (SUA), and the pathophysiology of this complication is poorly understood. Objective-To evaluate if changes in diameter of the remaining umbilical artery in fetuses presenting an isolated SUA are associated with different fetal growth patterns. Study design-This was a two-center prospective longitudinal observational study including 164 fetuses diagnosed with a SUA at the 20-22-week detailed ultrasound examination and 200 control fetuses with a three-vessel cord. In all cases, the diameters of the cord vessels were measured in a transverse view of the central portion of the umbilical cord, and the number of cord vessels was confirmed at delivery. Logistic regression and nonparametric receiver operating characteristic (ROC) analysis were carried out to evaluate the association of the umbilical artery diameter in a single artery with small for-gestational age (SGA) and with fetal growth restriction (FGR). The impact of artery dimension was adjusted for maternal BMI, parity, ethnicity, side of the remaining umbilical artery and umbilical resistance index (RI) in the regression model. Results-A significantly (p < 0.001) larger mean diameter was found for the remaining artery in fetuses with SUA compared with controls (3.0 ± 0.9 vs. 2.5 ± 0.6 mm). After controlling for BMI and parity, we found no difference in umbilical resistance and side of the remaining umbilical artery between the SUA and control groups. A remaining umbilical artery diameter of >3.1 mm was found to be associated with a lower risk of FGR, but this association failed to be statistical significant (OR = 0.60, 95% CI = 0.33-1.09, p value = 0.089). We also found that the mean vein-to-artery area ratio was significantly (p < 0.001) increased in the SUA group as compared with the controls (2.4 ± 1.8 vs. 1.8 ± 0.9; mean difference = 0.6; Cohen's d = 0.46). Conclusion-In most fetuses with isolate SUA, the remaining artery diameter at 20-22 weeks is significantly larger than in controls. When there are no changes in the diameter and, in particular, if it remains <3.1 mm, the risk of abnormal fetal growth is higher, and measurements of the diameter of the remaining artery could be used to identify fetuses at risk of FGR later in pregnancy.

Should fetal growth be a matter of concern in isolated single umbilical artery?

OBJECTIVE

To examine birth weight in pregnancies with isolated single umbilical artery (ISUA).

METHODS

Case control study with retrospective review of 131 singleton pregnancies with isolated single umbilical artery diagnosed before birth. Control group consisted of 730 singleton pregnancies recruited prospectively, that had histological confirmation of a 3 vessels cord. Pregnancies were classified as uncomplicated or high-risk according to the presence of diseases that increase the risk of placental insufficiency during pregnancy. Mean birth weight and frequency of low birth weight (< 2.500 g), very low birth weight (< 1.500 g) and fetal growth restriction below the 5th and 10th centiles were compared between groups.

RESULTS

Mean birth weight difference between ISUA (n=131, 2840±701g) and control (n=730, 2.983 ± 671g) pregnancies was 143g (95% CI= 17-269; p=0.04) and birth weight below the 5thcentile was significantly more common in ISUA group [28/131 (21.4%) versus 99/730 (13.6%), p=0.02]. When only uncomplicated pregnancies were considered in both groups, no birth weight differences were observed. Amongst high-risk subgroups, birth weight below the 5th centile remained significantly more common in ISUA compared to control pregnancies [10/35 (28.6%) versus 53/377 (14.1%), p=0.04].

CONCLUSION

Isolated single umbilical artery does not increase the risk of fetal growth restriction in uncomplicated singleton pregnancies.