Twin Ultrasound

Pregnancy scans & multiple pregnancy.

Twins and your ultrasound

Twins, and rarely higher multiples, can be identified through ultrasound. One of the medical reasons for “routine” ultrasounds for every pregnancy is so that they are detected. This is important both for the families and for medical care.

The scan is particularly valuable in determining the type of twinning, which can help assess the likelihood of complications. This assessment is most accurate during the first trimester, such as in an early pregnancy scan or the 12-14 Week scan.

Identifying the type of twins

Concepts about twins often get mixed up. In the community, the type of twins often refers to whether they are non-identical (fraternal) twins from separate eggs or identical twins from a single egg that splits after fertilisation.

Fraternal Twins

Develop from two separate eggs and are more common.
Can be the same sex or one of each.
Always have separate placentas (though they may appear joined) and separate inner sacs.
Are influenced by family history, maternal age (peaking at 35–39), and factors like ovulation induction.

Identical Twins

Result from a single egg that splits after fertilisation.
Are the most common twin type after IVF (with single embryo transfer).
Usually share a placenta and circulation and are always the same sex.
May have the same placental appearance as fraternal twins if the embryo splits very early (before Day 3).

How Ultrasound Helps

At 5–6 weeks, the yolk sac (a small visible structure) appears. By 7–8 weeks, the number of yolk sacs and the relationship between the outer sac (chorion) and the inner sac (amniotic membrane) help provide more clarity.

Identical Twins and Blood Vessels

Identical twins often have one placenta and two amniotic sacs, in which case they are called monochorionic diamniotic (MCDA) twins. They usually do well but are at higher risk. This is partly because of their shared blood circulation. This type of identical twins receive much closer ultrasound monitoring than dichorionic (DCDA) twins, in which there are 2 separate placentas.

Twin Pregnancies at QDOS

Even the lower risk dichorionic twin pregnancies still need more ultrasounds than single pregnancies, as ultrasound is the best type of test to check each baby separately. Because of the increased number of scans, you may meet all our staff during your twin pregnancy! Remember to state you have twins, each time when booking, so that we allow extra time.

Schedule Your QDOS Ultrasound Now

Receive professional, compassionate care from our experienced team. Book an ultrasound appointment at a time that works best for you and take the next step in your pregnancy journey.