What are the common complications in twin pregnancies?

Understanding complications in twin and triplet pregnancies

When you find out you’re expecting twins, triplets or more, it’s natural to feel excited and worried at the same time. You might start hearing new medical terms and want to understand what they mean for you and your babies.

Most people with a multiple pregnancy don’t experience serious complications. However, the risks are higher than in a single pregnancy, so your care will usually be more frequent and more detailed. You’ll often be monitored in a twin or multiples’ clinic, run by midwives and doctors with extra training and experience in caring for twins, triplets or more.

At your first specialist appointment, your team should explain how often you’ll be seen, which scans and tests you’ll have and who to contact if something doesn’t feel right. If you’re unsure what type of multiple pregnancy you have, you can ask your consultant to explain this and how it affects your monitoring.

You’re the advocate for your own health and your babies. If you’re unhappy with your care at any stage, you have the right to ask questions, seek a second opinion or move to a different hospital.

Key complications affecting twins, triplets or more

Some complications in multiple pregnancy happen because the babies share a placenta. Others relate to how each baby grows or when they’re born. Understanding the main issues can help you feel more prepared for conversations with your team.

Twin-to-twin transfusion syndrome (TTTS)

If your babies share a placenta, one of the main concerns is twin-to-twin transfusion syndrome (LINK - INF-16). In TTTS, some of the blood that should be shared evenly is passed from one ‘donor’ baby to the ‘recipient’ baby. The donor baby can become smaller with less amniotic fluid, while the recipient baby may have too much fluid and extra strain on the heart. TTTS affects around 10% to 15% of twins sharing a placenta and is monitored through careful growth and doppler scans.

Twin anaemia-polycythaemia sequence (TAPS)

TAPS (LINK - INF-17) also only affects pregnancies with a shared placenta. Tiny blood vessel connections mean one baby becomes anaemic, with too few red blood cells, and the other becomes polycythaemic, with too many. This imbalance can strain both babies’ hearts. TAPS is harder to spot than TTTS because the fluid around each baby can look similar, so it’s usually diagnosed with detailed doppler scans or sometimes after birth.

Twin reversed arterial perfusion sequence (TRAPS)

TRAPS (INF-18) is very rare. One baby develops as expected, but the other does not form into a baby who can survive. Blood vessels in the placenta connect them, so the developing baby has to pump blood for both. This can place serious strain on their heart, which may be seen on specialist ultrasound scans.

Selective intrauterine growth restriction (SIUGR)

It’s common for one baby to be a little smaller than the other, but sometimes the size difference is larger and one baby isn’t growing as expected. This is called selective intrauterine growth restriction (LINK - inf19). It often happens when the placenta isn’t providing enough nutrients to one baby. If the size difference goes beyond around 10%, you may be referred to a fetal medicine specialist for closer monitoring of growth and blood flow using dopplers. SIUGR can happen on its own or alongside TTTS.

Prematurity and time in neonatal care

Twins and triplets are more likely to arrive early. Around 60% of twins and around 75% of triplets or more are born before 37 weeks. Sometimes this is planned because of the risks of staying pregnant for longer, and sometimes labour starts on its own. Your consultant should talk with you during the second trimester about the chance of preterm birth, your birth options and what might happen if your babies need extra help.

If an early birth is likely, you’re often offered steroid injections to help your babies’ lungs mature. Many twins and triplets spend some time in the neonatal unit or special care baby unit so they can grow, learn to feed and get used to life outside the womb before going home.

Monitoring, treatment and protecting your own health

Because there’s more for your body to cope with in a multiple pregnancy, you’re also at higher risk of some conditions that affect your health. These are monitored closely at your antenatal appointments with blood pressure checks, urine tests and blood tests.

Preeclampsia is more common if you’re carrying more than one baby. It’s linked with raised blood pressure and protein in your urine and can affect both you and your babies. Symptoms may include swelling in your face, ankles and hands, severe headaches, vision changes and pain under your ribs. If you notice these symptoms, you should contact your maternity team straight away. Treatment may include medication, rest in hospital or, in severe cases, an earlier birth.

Gestational diabetes is also more likely in twin or triplet pregnancies. It means your body is struggling to manage blood sugar levels. You might feel very thirsty, need to wee more often, feel very tired or notice blurred vision. These can also be normal pregnancy symptoms, so gestational diabetes is often picked up through routine screening and urine testing. Once it’s diagnosed, treatment such as dietary changes, extra monitoring and sometimes medication usually keeps it under control.

Anaemia is common because your body is working hard to supply oxygen to you and your babies. Eating iron-rich foods, such as well-cooked red meat, lentils, beans, leafy green vegetables and iron-fortified cereals, can help. Your midwife or doctor may also recommend iron supplements if your blood tests show low haemoglobin. Symptoms can include tiredness, breathlessness, paleness and feeling faint.

HELLP syndrome is a rare but serious condition that can develop in late pregnancy or soon after birth. It can have similar symptoms to preeclampsia, such as headaches, nausea, indigestion with pain after eating, upper right abdominal or chest pain, pain on breathing in, shoulder pain, vision changes or swelling. Treatment is usually to deliver your babies, so if you experience any of these symptoms you should seek urgent medical advice.

Your team should explain any tests or treatments they recommend and give you time to ask questions. You can always ask for something to be repeated or written down if that helps you feel clearer.

Staying informed, reassured and supported

Reading about complications (LINK - complications guide) can feel frightening, but it’s important to remember that many of these conditions are rare and you’re being monitored for them throughout your pregnancy. Regular scans, blood tests and checkups are there to keep you and your babies as safe as possible.

You can help by going to every appointment you’re offered, using tools like our pregnancy tracker to keep on top of tests and scans, and listening to your body. Eating well, keeping moderately active if it feels comfortable and resting when you can all support your health during this demanding time.

If you’re ever worried about symptoms, if something feels different from usual, or if you have questions about your care, speak to your midwife, doctor or antenatal consultant. Reaching out early means problems can be picked up and treated quickly, and it gives you the chance to feel more informed and involved in decisions about your pregnancy and birth.