Usually, the umbilical cord is 22 inches long and consists of two arteries and one vein. The vein brings nutrients and oxygen to the fetus while the arteries dispose of waste products. In about 1 to 1.5 percent of pregnancies, the umbilical cord will have the usual one vein, but only one artery.
There are certain conditions which predispose the pregnancy to the two vessel cord. One is maternal age of 40 years or greater. Also, a pregnancy consisting of a female fetus has a higher incidence of a two vessel cord compared to a male fetuse. A history of diabetes mellitus, especially if poorly controlled, and taking certain medications like seizure medications contribute to the higher incidence of a two vessel cord as well.
The diagnosis of a two vessel cord is usually made by ultrasound performed in the second trimester. The two vessel cord can be associated with heart, kidney, and spine abnormalities along with poor fetal growth known as intrauterine growth retardation (IUGR). For this reason, your doctor will order a more detailed followup ultrasound (known as a level II ultrasound) to evaluate these anatomical structures and to keep an eye on the growth of the fetus.
A fetal echocardiogram and genetic studies will also be recommended if there is a diagnosis of a two vessel cord.
Once the fetus is viable, your doctor may also start requesting weekly or twice weekly nonstress tests (NSTs). The NST is a painless test where a belt is placed around your pregnant abdomen, and the heart rate of the fetus is observed on a monitor. The heart rate pattern will let your doctor know if the fetus is doing well or not. Your doctor may also order a weekly biophysical profile (BPP) which is a special ultrasound that monitors your infant’s growth along with the amount of amniotic fluid, infant’s breathing, muscular tone, and movement.
It was thought, at one time, that having a two vessel cord increased the chances of stillbirth. Over the past few years, the incidence of stillbirth has not been greater in pregnancies with two vessel cords compared to those with three vessel cords. The lack of increased stillbirths may be due to the increased surveillance testing using the BPP and the NST, but the important thing is that stillbirths are not increased.
A two vessel cord will not predispose you to a cesarean section.
Remember that not all pregnancies with two vessel cords will have problems. It just means that your doctor will follow your pregnancy more closely.
Wishing you a happy and uncomplicated pregnancy and delivery.