Single umbilical artery is one of the most common congenital anomalies with a reported incidence of 0.2-1.2% in live newborns [1]. The incidence is higher (0.3-7%) among twins, fetal deaths, abortuses and autopsies [2,3]. The rate of associated congenital anomalies with single umbilical artery is about 10% as reported by a National Registry [4].

Perinatal autopsy was carried out in 214 cases within a span of 5 years in our center. These fetuses were either aborted due to intrauterine death or after prenatal detection of a malformation. The study was approved by the Institutional ethics committee.

Single umbilical artery was noted in 17 (9 males) fetuses (7.9%). The gestational age of the fetuses ranged from 12 to 39 weeks. All the pregnancies were singletons. Karyotype was done in 6 cases and was normal in four of them. On autopsy, congenital anomalies and/or growth abnormalities were detected in sixteen fetuses. Of the 17 fetuses, 14 had associated major fetal anomalies detected in the antenatal ultrasonogram, while the remaining three had oligohydramnios, intrauterine growth retardation and a choroid plexus cyst, respectively. There was predominant involvement of genito-urinary system in six cases followed by central nervous system in 4 cases. Intrauterine growth retardation, chromosomal abnormalities (trisomy 13 and Turner syndrome), posterior urethral valve with hydroureteronephrosis and neural tube defect were noted in two cases each. There were eight cases with single system involvement while seven fetuses had multisystem involvement. One fetus had intrauterine growth retardation without any associated anomalies. The detailed description of the cases is provided in Web Table I. Two of these cases have been published earlier [5,6].

The single umbilical artery is known to be associated with poorer perinatal outcome compared to those with two arteries. The incidence of single umbilical artery at perinatal autopsy in our study is similar to the incidence (7.01%) reported by Csecsei, et al. [1]. The rate of chromosomal anomalies has been found to be significantly higher (8-11%) among fetuses with single umbilical artery compared to those with two umbilical arteries [7,8]. In our study, chromosomal abnormalities were noted in two fetuses with single umbilical artery and six fetuses without single umbilical artery (11.7% vs 2.8%). Similar to previous reports [2,9], our study also shows involvement of urinary system in majority of fetuses.

The etiopathogenesis of absence of one of the umbilical artery is not clear till date. Abuhsmad, et al. [10] hypothesized that it could be due to primary agenesis or atrophy of one of the arteries or the persistence of the original allantoic artery in the body stalk of embryo. Also, the poorer perinatal outcome and association of other fetal anomalies in fetuses with single umbilical artery is not clearly understood till date. However, it is important to look for other associated anomalies when single umbilical artery is diagnosed antenatally or postnatally. We conclude that single umbilical artery warrants a detailed evaluation of the fetus for other anomalies.

Funding: Indian Council of Medical Research (BMS No. 54/5/2010); Competing interest: None stated.