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Background: Single umbilical artery (SUA) is found in 0.5–6% of all pregnancies worldwide. Although the association of SUA with some congenital malformations is mainly accepted, its effect on pregnancy/neonatal outcomes is still controversial. Objective: This is the first study aimed to approximate the SUA prevalence in southern part of Iran. SUA epidemiologic features accompanied by some of its effects on pregnancy/neonatal outcomes are investigated as well. Materials and Methods: In this cross-sectional study, data from two referral centers in Southern Iran were analyzed. In total, 1,469 pregnancies, fetuses, and neonates were examined for epidemiological features associated with SUA. SUA was confirmed by pathological examination, while congenital anomalies were diagnosed by clinical, ultrasound, and echocardiographical examinations. Data on pregnancy outcome were recorded based on the patients’ medical records. Results: The prevalence of SUA was 3.47% (95% CI: 2.6–4.6%). Fetal anomalies including renal, cardiac, and other congenital anomalies, intrauterine fetal death, early neonatal death, low birth weight, low placental weight, and preterm birth were significantly higher in the SUA group (OR = 68.02, 31.04, 16.03, 3.85, 11.31, 3.22, 2.70, and 2.47, respectively). However, the maternal multiparity was lower in the SUA group (OR = 0.65; 95% CI: 0.44–0.98). Conclusion: A significant association was observed between SUA and increased risk of intrauterine fetal death and early neonatal death, as well as low birth weight and preterm birth. Obstetrical history of the mother like parity was identified as an important predictor of SUA. Further investigations are suggested on risk stratification of neonates in this regard.   Key words: Umbilical cord, Single umbilical artery, Pregnancy outcome, Congenital abnormalities.

percent of case patients bed-shared compared with 13% of control patients. Overall, bed-sharing was associated with an increased risk of SIDS (11 studies, N58,959, OR 2.89; 95% CI,. When bedsharing was not routine and only performed on the "last sleep," the risk of SIDS increased (four studies, total number participants not stated, OR 2.18; 95% CI, 1.45-3.28). SIDS risk was not increased when bedsharing was routine (two studies, total number participants not stated, OR 1.42; 95% CI, 0.85-2.38). An increased risk of SIDS was observed when there was maternal smoking and bed-sharing (4 studies, total number participants not stated, OR 6.27; 95% CI, 3.94-9.99), but not for nonsmokers (3 studies, total number participants not stated, OR 1.66; 95% CI, 0.91-3.01). Bed-sharing with infants ,12 weeks old increased the risk of SIDS (3 studies, total number participants not stated, OR 10.37; 95% CI, 4.44-24.21), but not with infants .12 weeks old (3 studies, total number participants not stated, OR 1.02; 95% CI, 0.49-2.12). A potential limitation of this meta-analysis was that the studies spanned from 1987 to 2006 which was both before and after the "back to sleep" campaign which started in 1994 that decreased the overall rate of SIDS. Another limitation was the diversity in methods across studies, although confounders such as socioeconomic status and sleeping position were controlled.