Twin pregnancy: extra scans, risks and when twins are usually born

Finding out you’re having twins is a lot to take in. Here’s what the NHS says about the extra care you’ll be offered, the scans, the risks and when twins are usually born.

Types of twins

Your care depends on whether your babies share a placenta and a sac (‘chorionicity’). The NHS describes three types:

DCDA: separate placentas and separate sacs. All non-identical twins are this type.
MCDA: a shared placenta but separate sacs. Most identical twins are this type.
MCMA: a shared placenta and sac. This is much rarer.

Scans and appointments

You should be offered an ultrasound scan at around 11 to 14 weeks, which is the best time to work out which type of twins you’re having and to check your dates. A cervical length scan at 16 to 20 weeks may also be offered, and a short cervix may mean daily progesterone tablets until 34 weeks. You’ll have the anomaly scan at 20 weeks. See 12-week scan and 20-week anomaly scan.

After that, with DCDA twins you’ll usually be scanned every 4 weeks (NHS). If your babies share a placenta (MCDA), the NICE guideline says you should be scanned every 2 weeks from 16 weeks until birth. MCMA twins need more scans and monitoring, and may be referred to a specialist fetal medicine centre. The NHS says your antenatal team should be experienced in caring for women having twins or triplets.

Risks

The NHS lists premature birth, low birthweight, pre-eclampsia and iron deficiency anaemia. Around 6 in 10 twins are born before 37 weeks. Twin-to-twin transfusion syndrome affects 10 to 15% of twins who share a placenta, and your scans watch for it. Many twins are born healthy.

See high blood pressure and pre-eclampsia and anaemia and iron tests.

When will my twins be born?

The NHS says planned birth is usually recommended at:

37 weeks for twins with separate placentas (DCDA)
36 weeks for identical twins sharing a placenta (MCDA)
32 to 33 weeks for twins sharing a sac (MCMA)

The NHS says it can be dangerous for a multiple pregnancy to continue past these dates. If you’d rather wait, you should be offered weekly obstetrician appointments, weekly scans and a growth scan every 2 weeks. Your team will talk through whether a vaginal birth or caesarean is right for you.

Support

Twins Trust runs a free helpline on 0800 138 0509, open Monday to Thursday 10am to 1pm and 7pm to 10pm, excluding bank holidays. You don’t need to be a member.

Questions people ask

Can I have twins naturally?

Many people do. The NHS page doesn’t cover birth method, so talk through vaginal birth and caesarean with your team.

Why do I need so many scans?

Twins are watched more closely for growth, and for problems such as twin-to-twin transfusion in babies who share a placenta. With separate placentas, the NHS says scans are usually every 4 weeks.

Will my twins be early?

Probably, and that’s planned. The NHS says around 6 in 10 twins are born before 37 weeks, and planned birth is usually recommended at 36 or 37 weeks.

Do I need extra vitamins?

Ask your midwife. The general advice is in folic acid and pregnancy vitamins.