[Arterial-adaptive dilatation and Doppler velocimetry in normal fetuses with a single umbilical artery]

Comparative study of umbilical cord cross-sectional area in foetuses with isolated single umbilical artery and normal umbilical artery

Single umbilical artery (SUA) is one of the most common prenatal diagnoses in cases of foetal abnormality. This prospective study evaluated 77 foetuses with isolated SUAs and 77 healthy foetuses, both at 22-39 gestational weeks. We categorised gestational age into the second and third trimesters, measured the umbilical arterial blood flow parameters and calculated the umbilical vein (UV) area, umbilical artery (UA) area and UV area/UA area ratio. In the second and third trimesters, a higher UA area was obtained in the isolated SUA group than in the control group (p < .01). Furthermore, the isolated SUA group had a lower UV area/UA area ratio than the control group (p < .01), and a positive linear correlation was found between gestational age and UV area in both groups (p < .01). The presence of isolated SUAs was associated with low birth weight and a high prevalence of small for gestational age.IMPACT STATEMENTWhat is already known on this subject? Single umbilical artery (SUA) is one of the most common prenatally diagnosed foetal abnormalities and approximately 80% foetuses with SUA have isolated SUA, which is a soft indicator of chromosome abnormalities, congenital malformations and premature birth. Umbilical cord cross-sectional area can be evaluated prenatally by ultrasound imaging. Normal values increase with gestational age and foetal size in single pregnancies. Changes in umbilical cord thickness have been associated with complications during pregnancy.What do the results of this study add? The correlation between gestational age and umbilical vein area in the isolated single umbilical artery (SUA) group and control group was better than that between gestational age and umbilical artery area. UA area increased significantly in both groups before 28 weeks but not after 28 weeks, particularly in the isolated SUA group.What are the implications of these findings for clinical practice and/or further research? The study provides a reliable basis for maternal foetal monitoring during pregnancy in the isolated SUA and control groups. Objective assessment of the occurrence and development of foetuses with isolated single umbilical artery was performed.

Intrauterine Transfusion Complicated by Umbilical Artery Thrombosis

Background

Fetal anemia results from several conditions; however intrauterine transfusion (IUT) remains the treatment for severe cases. The complications of this procedure are rare and yet can result in preterm delivery or fetal death.

Case

31 y/o G3P2002 with Rh alloimmunization underwent IUT from 19 to 35 weeks. Umbilical artery thrombosis was noted after her 5^th IUT. Further transfusions were performed without any complications and she delivered a full term male infant with APGARS of 8 and 9 at 1 and 5 minutes, respectively.

Conclusion

The complication of umbilical artery thrombosis is unusual and the optimal management is unclear. We report such a case and propose that the presence of Hyrtl's anastomosis near the placental cord insertion may explain the reassuring fetal status throughout the pregnancy.

Isolated single umbilical artery in twin pregnancies and its adverse pregnancy outcomes - a case report and review of literature

Single umbilical artery is the most common congenital abnormality of the umbilical cord and is seen in 4-11% of twin pregnancies. It is usually associated with intrauterine growth retardation, preterm labour, small-for-dates and other structural anomalies. There is no significant difference in the incidence between monochorionic and dichorionic twins. The left artery is usually absent more commonly than the right. The female co-twin was predominantly more affected than their male counterparts. Single umbilical artery is found twice more common in white women than in Afro-Asians and Americans. The hemodynamic disturbances occur early in the embryonic development, influence greatly in the development of single umbilical artery. Genetic and environmental factors also play a major role in the development of this anomaly. The pregnancies with single umbilical artery were classified as high risk group, because the overall perinatal mortality rate was estimated to be as high as 20%. There is a significant increase in the occurrence of single umbilical artery in pregnancies due to artificial reproductive technologies, as well as in spontaneous miscarriages. Prenatal ultrasonography is the principal diagnostic technique employed to identify single umbilical artery during 3(rd) trimester of pregnancy. The present case, reports the presence of a single umbilical artery in a monozygotic, monochorionic twin pregnancy, which is acardiac-acephalic fetus, small for dates, female sex, associated with other major structural anomalies, and was still born. Authors analyse its incidence, clinical presentations and pregnancy outcome and also review the pertinent literature.

Single umbilical artery in twin pregnancies

OBJECTIVE

Our purpose was to evaluate the antenatal incidence of single umbilical artery (SUA) in twin pregnancies according to chorionicity and to assess its relationship with outcome.

METHODS

Consecutive twin pregnancies undergoing ultrasound evaluation at our institutions were included. A targeted sonographic evaluation of the umbilical cord and vessels was performed in all cases. Chorionicity was determined according to standard ultrasound criteria.

RESULTS

A total of 174 twin pregnancies, 100 dichorionic (DC) and 74 monochorionic (MC), were included in the study. An SUA was identified in 17 (9.8%) pregnancies, and in 18 (5.2%) fetuses. No difference was found in the incidence of SUA in DC and MC twins. Among affected pregnancies, all but one DC twin pregnancy were discordant for SUA. Structural and/or chromosomal abnormalities were present in 27.8% of fetuses with SUA. The prevalence of small-for-gestational-age fetuses and of discordant birth weight (> 20% discordance) was higher in the SUA group than in the rest of the population, although these differences were not statistically significant. Twin pairs discordant for SUA had significantly higher weight discordance than those with normal umbilical cords. The sonographic cross-sectional area of the SUA did not appear to show the typical adaptive dilatation usually seen in singleton pregnancies with SUA.

CONCLUSIONS

The incidence of SUA in twins is higher than in singletons, with no difference between MC and DC twins. Intrapair discordance for SUA in identical twins provides evidence against an exclusively genetic origin of this anomaly. The apparent failure of compensatory dilatation of the umbilical artery in twins with SUA may explain in part the higher risk for fetal growth restriction in these cases.