The normal structure and Doppler parameters of the umbilical cord are closely related to many diseases, including fetal infection, chromosomal abnormalities, hypoxia, and growth and development restrictions. We report a case of bilateral umbilical artery confluence resulting in the formation of a single umbilical artery in the free segment of the fetal umbilical cord, diagnosed at 24 weeks and 4 days gestation. The fetus was born prematurely after premature membrane rupture at 31 weeks and 3 days gestation. The Toxoplasma, Others, Rubellavirus, Cytomegalovirus, Herpesvirus test showed positive results for Toxoplasma gondii, rubella virus, and herpes simplex virus IgG antibodies. A 36-year-old woman had vaginal discharge for > 1 hour at 31 weeks + 3 days gestation and came to our obstetrics department for treatment. The pregnant woman sought treatment due to premature membrane rupture and vaginal discharge for > 1 hour. The vaginal discharge was caused by Escherichia coli. After cesarean section, the Toxoplasma, Others, Rubellavirus, Cytomegalovirus, Herpesvirus test revealed positive results for the following: T gondii, rubella virus, and herpes simplex virus IgG antibodies. The patient underwent 2 ultrasound examinations and was diagnosed with umbilical artery malformation (the free segment of the umbilical cord on the fetal side converged into a single umbilical artery), which may have been related to fetal infection. The patient received anti-inflammatory and fetal lung maturation treatment for 2 days before undergoing a cesarean section. The mother and newborn received anti-inflammatory, symptomatic, and supportive treatment and were discharged after 1 week of improvement. After 1 month, 6 months, and 1 year of follow-up after birth, the growth and development of the infant (height and weight) were significantly lower than those of her peers, and her responses to sound and light were slightly delayed. Umbilical artery malformation is extremely rare and may be related to intrauterine parasitic and viral infections. Ultrasound has the advantages of being noninvasive and cost-effective and can be used to dynamically observe umbilical artery structure. An abnormal change in umbilical artery structure found during ultrasound examination can indicate intrauterine infection risk, which provides clinical guidance for further examination of pregnant women, early diagnosis, timely targeted treatment, and fetal prognosis improvement.