Table 1.

General classification of UCA.

	Pathology		Incidence	Risk Factors	Associated Pathology	Adverse Outcome	Reference
Placental Insertion Anomalies	Velamentous Cord Insertion		0.23–1% singleton gestation 15% monochorionic twin pregnancy	▪ART (IVF), low lying placenta, placenta praevia ▪Accessory lobe or bilobated placenta ▪Multiple pregnancy	▪Vasa praevia ▪Single umbilical artery—12.5% of cases ▪Fetal anomalies	Intrauterine growth restriction, preterm labor, placental abruption, low Apgar score, intrauterine fetal death, acute fetal distress by rupture, kinking, or compression of the cord insertion, hemorrhage and obstetrical maneuvers for placental retention in the third stage of labor, vessel thrombosis with placental infarction and distal segment fetal amputation, neonatal purpura, twin–twin transfusion syndrome	[14,22,23,24,25,26,27,28,29]
	Vasa praevia		0.0004–0.08%	▪Second-trimester low-lying placenta or placenta praevia, bilobed or succenturiate lobe placenta ▪Assisted reproductive technologies ▪Velamentous cord insertion ▪Vaginal bleeding ▪Multiple gestation ▪First trimester umbilical cord insertion in the lower 1/3 of the uterus	▪Fetal heart abnormalities	Preterm birth (<32 weeks), SGA neonate, neonatal death, postpartum hemor-rhage, emergency cesarean section, elective cesarean section, admission to NICU, neonatal blood transfusion	[16,25,30,31]
	Eccentric/Marginal Cord Insertion		7% singleton pregnancy 25% twin pregnancy	Advanced maternal age (≥35 years) Chronic maternal pathologies Female fetus Marginal cord insertion in previous pregnancy		Intrauterine growth restriction, preterm labor, progression to velamentous cord insertion, high risk of cesarean section, low Apgar score Fetal malformations, NICU admission, preeclampsia, emergency and elective cesarean section	[27,31,32,33]
Fetal Insertion Anomalies	Omphalocele and gastroschisis		0.08%	▪Extreme ages (under 20 and over 40 years) ▪Maternal obesity ▪Inconstantly demonstrated teratogenicity caused by selective serotonin reuptake inhibitors	▪Fetal aneuploidies, ▪Gastrointestinal abnormalities ▪Cardiac defects ▪Genitourinary, orofacial and diaphragmic malformations ▪Neural tube defects ▪Polyhydramnios ▪Cantrell pentalogy, ▪Amniotic bridle sequence ▪Fusion defect association ▪OEIS syndrome, Shprintzen syndrome, Carpenter syndrome, Goltz syndrome, Meckel–Gruber syndrome, CHARGE syndrome and Beckwith–Wiedemann syndrome	Intrauterine growth restriction, prematurity, elective cesarean section	[34,35,36,37,38,39,40]
Positional anomalies Cord anomalies		Nuchal Cord	Between 35% and 0.6% (>3 loops)	▪Excessive fetal movement ▪Excessive long umbilical cord ▪Monoamniotic twins ▪Number of loops increases with gestational age ▪Male fetuses	Cord knot	Intrauterine growth restriction, acute fetal distress, perinatal death, stillbirth, operative vaginal delivery, emergency cesarean delivery, need of oxygen supplementation at delivery	[41,42,43,44,45,46,47]
		Cord Knot	0.3–1.3%	▪Advanced maternal age ▪Multiparity ▪Obesity ▪Previous spontaneous abortion ▪Chronic hypertension ▪Gestational diabetes	Long umbilical cord length	Prematurity, low Apgar score, NICU admission, emergency cesarean delivery, elective cesarean delivery, antepartum and intrapartum fetal death (likelihood of stillbirth is more than 4-fold higher)	[17,48,49]
		Cord Strictures	rare	Twin pregnancy	▪Umbilical cord overcoiling ▪Long umbilical cord length	Intrauterine growth restriction, Intrauterine fetal death	[50]
	Structural anomalies	Single Umbilical Artery	0.55–5.9%	▪Extremes of maternal age ▪Diabetes ▪Smoking ▪Hypertension ▪Twin pregnancy	▪Genitourinary malformations ▪Caudal regression syndrome ▪Sirenomelia ▪Cardiac anomalies ▪Gastrointestinal anomalies ▪Musculoskeletal anomalies ▪Central nervous system anomalies	High rate of pregnancy loss Intrauterine growth restriction Iatrogenic prematurity	[51,52,53,54,55,56,57]
		Umbilical artery hypoplasia	0.04%	Maternal diabetes mellitus	▪Placentation anomalies ▪Abnormal placental cord insertion ▪Trisomy 18 ▪Agenesis of corpus callosum ▪Cardiac anomalies ▪Genitourinary minor malformations ▪Polyhydramnios	Intrauterine growth restriction	[58]
		Supernumerary vessels (Right Umbilical Vein Persistence)	0.5%	▪Twin pregnancy (thoracopagus and omphalopagus twins) ▪Thrombus obstruction, teratogens or folic acid deficiency ▪Female fetuses	▪Anterior chest wall defects ▪Bilateral cleft lip and palate ▪Placental arteriovenous fistula ▪Edema ▪Heterotaxy syndrome ▪Trisomy 18 ▪Holoprosencephaly ▪Polyhydramnios ▪Omphalocele ▪Triploidy ▪Hypertrophic cardiomyopathy ▪Ectopia cordis ▪Tetralogy of Fallot ▪Ductus venosus agenezia (DV)	Intrauterine growth restriction	[59,60,61,62]
		Umbilical Cord Cyst	2–3%	Chromosomal anomalies	▪Fetal aneuploidies ▪Omphalocele ▪Vertebral defects ▪Imperforate anus ▪Tracheoesophageal fistula ▪Radial and renal dysplasia association ▪Angiomyxoma of the cord	Rapid enlargement with the restriction of blood flow and fetal distress requiring emergency birth. Torsion or thrombosis may cause fetal demise	[63]
		Cord Hematoma	9 × 10−5	▪Umbilical blood sampling ▪Fetal transfusion	Fetal bradycardia	Modified umbilical artery flow velocimetry, perinatal hypoxia, miscarriage	[64,65]
		Cord Varix/Aneurysm	0.0011%	▪Chromosomal anomalies ▪Single umbilical artery ▪Male fetus	▪Chromosomal anomalies ▪Anatomical abnormalities ▪Single umbilical artery	Intrauterine death by aneurysm rupture or varix thrombosis, fetal hydrops, SGA, invalidated neurodevelopmental delay	[61,66,67]
		Cord Tumors: angiomixomas, mixosarcomas, coriomixomas, hemangiomas, teratomas	Isolated cases	Twin pregnancy for teratomas	Teratomas assoaciate: ▪Omphalocele ▪Trisomy 13 Angiomyxoma assoaciate: ▪ Skin hemangiomas	Intrauterine death due to torsion or compression effect on umbilical cord vessels	[68,69]
	Coiling and length anomalies	Excessive/Absent Coiling	4–5%	Abnormal placentation	Single umbilical artery	Fetal growth restriction, congenital anomalies, fetal heart rate abnormalities, preterm birth, intrauterine death	[70]
		Abnormally short/long Cord	8.26%	Fetal malformations	▪Fetal malformations ▪Myopathic and neuropathic diseases	Fetal inactivity in cases of short umbilical cord, oligohydramnios, placental pathology, fetal growth restriction, long cord entanglement and intrauterine asphyxia and fetal death.	[71,72,73]