Normal length 55-60cm, 1-2cm diameter (up to 3cm with excess Wharton's jelly)
    <30cm can have difficult vaginal delivery
    >100cm risk of knots
     umbilical vein empties into ductus venosis (40%) and portal system (60%)
     umbilical arteries arise from internal iliac arteries    

Three vessel cord doppler - (normal circulation)
        two arteries are best seen coursing on both sides of the bladder
       arterial waveform is low resistance (RI<0.7, with Systolic/Diastolic ratio<3) that increases slightly with GA >40wks.

• S/D ratio >4 suggests IUGR.
• normal doppler in small GA fetus is likely to have normal outcome
• absent or reversed diastolic flow is highly specific for fetal distress and is suggestive of imminet fetal demise

Two vessel cord - occurs in 1% of pregnancies and 50% of the time is associated with chromosomal anomalies and fetal malformations. If no malformations found, amniocentisis is not usually performed.
NB persistent Right umbilical vein (ie 4 vessel cord) associated with lethal anomalies

Umbilical cord masses
    cysts: remnants of vitelline or allantoic duct (small 4-6mm), rarely associated with omphalocele
    hemangiomas: can have associated elevated alpha fetoprotein, hydrops, hemorrhage
    hematomas: usually with cord manipulation or puncture
    vein thrombosis: not always fatal, particularly if normal size cord

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