Early Pregnancy Ultrasound: Are you having twins?

OMNI will confirm or exclude the presence of twins using high resolution ultrasound evaluation of the pregnancy. Multiple births include twins and higher order multiples (e.g. triplets, quadruplets). An early pregnancy scan can determine the number of fetuses (singleton or multiple) present.

The prevalence of multiple births has been increasing because of more widespread use of assisted reproductive technologies (ARTs) to treat infertility. The use of fertility drugs such as clompihene and other ARTS such as IVF or GIFT has contributed to the increasing number of higher order pregnancies.

Having diagnosed a twin pregnancy at the 1st trimester scan, it is important to determine if the fetuses have separate placentas or share the same placenta. This is referred to as the chorionicity and ultrasound gives us the answer. If the fetuses have separate placentas, then this is known as dichorionic (DC) twins. If however the babies share the same placenta, then this is known as monochorionic (MC) twins.

Why is it important to determine the number of placentas or chrorionicity? Twin to Twin Transfusion Syndrome (TTTS) occurs in twins that share the same placenta (MC twins) and not in DC twins. TTTS is a condition in pregnancy that exists when blood passes disproportionately between twins with a shared placenta. This causes one twin to receive less than normal amounts of blood supply during pregnancy while the other receives too much. There are degrees to the severity of the syndrome, and it can be life-threatening due to the fact that it can worsen at anytime during pregnancy. Therefore it is important to distinguish between MC and DC twins in the first trimester at an early ultrasound examination. The earlier the scan is performed in pregnancy, the easier this can be achieved. Once the chorionicity is known, then your Obstetrician can plan your pregnancy, frequency of interval scans and follow up accordingly.