Complications of twin (multiple) pregnancies

Twin pregnancies, as with all multiple pregnancies, carry greater risks for the mother and baby than ‘singleton’ pregnancies.

Having twins increases the risk of many of the complications of pregnancy, such as intrauterine growth restriction (IUGR), pre-eclampsia, and gestational (pregnancy-related) diabetes. Twin pregnancies also have complications of their own.

During antenatal care, labour and delivery, and in the neonatal period immediately after birth, twin pregnancies should be treated as high risk. Twin births need careful planning to ensure that delivery takes place in a way that is best for the mother and babies’ safety with skilled obstetric care available to manage the delivery.

Regular scanning and monitoring must take place to ensure that complications are detected early. This includes electronic fetal heart monitoring during labour and delivery. With correct care, additional scanning and monitoring in pregnancy, proper advice and planning the method of delivery for the birth, and correct and skilled management of labour and delivery, many of the risks of twin pregnancy can be managed or avoided.

What are the different types of twin pregnancy?

We tend to think of twins as either identical or non-identical but, in medical terms, twin pregnancies are classified according to whether the babies’ share the placenta and its inner and outer membranes.

There are three types of twins:

DCDA or dichorionic diamniotic twins

DCDA twin babies each have their own placenta with its own amnion or separate inner membrane and chorion or outer membrane. Non-identical twins are always DCDA. One third of identical twins are DCDA. DCDA twin pregnancies are lower risk than other types of twins. 

MCDA or monochorionic diamniotic twins

MCDA twin babies share one placenta with a single outer membrane and two inner membranes. Two thirds of identical twins are MCDA.

MCDA twin pregnancies are at highest risk of twin-to-twin transfusion syndrome or TTTS, a dangerous abnormality of the placenta which can be life-threatening for one or both babies. MCDA twins must be scanned and monitored more often than other twin pregnancies. The mother of MCDA twins may be referred to a fetal medicine centre for specialist care during her pregnancy.

MCMA or monochorionic monoamniotic twins

MCMA twin babies share one placenta and both the inner and outer membranes. MCMA twin pregnancies are rare. 1 in 100 identical twin pregnancies are MCMA. MCMA twins have an increased risk of cord entanglement, a life-threatening complication of pregnancy for the babies. They need specialist care with close monitoring and frequent scanning.

Each type of twin pregnancy has its own risks. The type of twin pregnancy and its risks determine the level of care that must be given during pregnancy, such as the frequency of antenatal appointments, tests and scans.

Parents can find out which type of twins they have at the antenatal ultrasound scan appointment. This important appointment usually takes place at around 11 to 14 weeks of pregnancy. In addition to finding out about the type of twins, this appointment also helps confirm the expected date of delivery and includes Down Syndrome screening.

Complications of twin pregnancy

Twin pregnancies or multiples, such as triplets, have a higher risk of suffering complications of pregnancy, such as:


Anaemia in pregnancy often arises from lack of iron and can often be treated with iron tablets, folic acid supplements and changes to diet. Untreated anaemia increases the risks of harm from maternal and fetal death, IUGR, infection, heart failure and bleeding.

Hypertension (high blood pressure), pre-eclampsia and HELLP syndrome

Mothers of twins have more than twice the risk of other pregnant women of developing hypertension (high blood pressure). Hypertension often starts earlier and becomes worse in twin pregnancy than where the mother is carrying a single baby. Having high blood pressure in pregnancy increases the risk of placental abruption (early detachment of the placenta). It can also be a sign of other serious conditions.

Hypertension and protein in the pregnant mother’s urine (proteinuria) are signs of pre-eclampsia. Pre-eclampsia needs careful monitoring as it can be dangerous for both mother and baby if left untreated.

Other symptoms of pre-eclampsia include severe headaches, swelling (oedema) of the ankles, face or hands, visual disturbance and abdominal pain. Pre-eclampsia is usually treated by admission to hospital, bedrest, medication and careful monitoring, to reduce the mother’s blood pressure to safe levels. Where the mother’s blood pressure remains high, the only way to avoid the risk of serious injury may be to deliver the baby prematurely.

HELLP syndrome is a very dangerous condition which is similar to pre-eclampsia. The syndrome’s name, HELLP, is an acronym which comes from the key features of the condition:

  • Haemolysis (breakdown of red blood cells)
  • ELevated liver enzymes
  • Low Platelet count (affecting blood clotting)

Pregnant women with HELLP syndrome need urgent treatment to avoid serious injury to both mother and baby. HELLP syndrome is often mistaken for other conditions. When this happens, the mistaken diagnosis can lead to delays in vital treatment.

Signs and symptoms of HELLP syndrome include:

  • hypertension
  • proteinuria
  • swelling (oedema)
  • visual disturbance
  • headache
  • nausea and vomiting
  • indigestion
  • pain, such as in the upper body, when breathing deeply

In many cases, HELLP syndrome can only be treated by early delivery of the baby and a blood transfusion for the mother. Untreated HELLP syndrome can cause maternal death or critical illness from liver rupture or stroke. It can also lead to stillbirth or brain injury to the unborn baby from placental failure or abruption.

IUGR or intrauterine growth restriction

Twins are often naturally smaller than babies in a single pregnancy. Twin babies’ growth should be carefully monitored and charted in pregnancy. Reduced growth of one or both twins may be a sign of problems with the placenta or the umbilical cord, which may put the babies’ lives at risk. 

Women with twin pregnancies should have regular ultrasound scans to monitor their unborn babies’ growth so that problems can be detected, and treatment or early delivery can be carried out, if necessary for the babies’ safety.

Gestational diabetes

Where gestational (pregnancy-related) diabetes arises in pregnancy, it can often be controlled by diet and exercise. In severe cases, tablets or insulin injections may be required to keep the mother’s blood sugar within safe levels.

Uncontrolled diabetes increases the risk of other complications of pregnancy, such as high blood pressure and pre-eclampsia, big babies and shoulder dystocia, stillbirth, premature birth, and neonatal problems, such as respiratory (breathing) difficulties, hypoglycaemia (low blood sugar) and jaundice.

Premature birth

The most common complication of twin and other multiple pregnancies is premature birth (before 37 weeks of pregnancy) and low birth weight (below 5.5lb). 60% of all twins and 80% of all triplets are born prematurely.

Premature birth is risky for the baby, particularly if they are born before their organs have had the chance to develop fully. The lungs are among the latest of the baby’s organs to develop. For this reason, pregnant women who go into labour prematurely are often given steroids to help the baby’s lungs develop quickly and reduce respiratory problems after birth.

Premature babies usually need care in a neonatal intensive care unit (NICU or SCBU) after birth. This may be because they need help with breathing and feeding or because they are struggling to control their body temperature or fight infection.

Premature babies are at risk of other serious conditions, such as retinopathy of prematurity (ROP) which arises when a baby is born before the retina in their eyes have developed properly. Premature babies are known to be at risk of ROP and must be carefully monitored for signs of ROP after birth. Delay in diagnosis and treatment of ROP can lead to permanent blindness.

TTTS (twin to twin transfusion syndrome)

Twin to twin transfusion syndrome (or TTTS) is a condition which can affect monochorionic twins (identical twins sharing a single placenta). MCDA twins have the highest risk of TTTS, but MCMA twins can also be affected.

TTTS happens when abnormal connections between blood vessels in the placenta allow blood to flow to the unborn babies in an unbalanced way. In twins with TTTS, one baby gets more blood supply than the other. The ‘donor twin’ doesn’t get enough blood and is undernourished and anaemic. The ‘recipient twin’ may have heart failure from too much blood and other problems from too much amniotic fluid.

If a woman who is pregnant with monochorionic twins experiences one or more of the following ‘red flag’ warning symptoms for TTTS, she should seek medical help straight away:

  • Sudden abdominal distension (or swelling);
  • Abdominal pain;
  • Sudden breathlessness;
  • Inability to lie on her back;
  • Reduced fetal movements.

When TTTS is suspected in a twin pregnancy, the unborn twins must be carefully monitored with frequent ultrasound scanning to check on their growth and wellbeing. The mother may need to be referred urgently to a fetal medicine centre for specialist treatment. 

Delays in diagnosis, referral to a fetal medicine specialist centre and treatment of TTTS can result in death or hypoxic (lack of oxygen) brain damage to the baby.

Breech presentation and delivery

When an unborn baby is positioned in the womb with their bottom or feet down (instead of head down) in the final weeks of pregnancy this is known as a breech presentation. 

Breech presentation can occur in any pregnancy, but it is common in twin pregnancies for one twin to be in the breech position. Planned caesarean section is often recommended in twin pregnancy where the first twin is in the breech position. Where the mother goes into labour spontaneously, it may be safer for the babies to be delivered vaginally by an obstetrician (childbirth doctor) who is skilled in vaginal breech delivery.

Twin deliveries should take place in hospital under the care of a multi-disciplinary maternity team including midwives, an obstetrician and paediatricians. The unborn twins must be carefully monitored throughout labour and delivery using electronic fetal heart monitoring, such as CTG or fetal scalp electrode.

Claims can arise where babies have suffered a brain injury from hypoxia or trauma as a result of incorrect management of the twins’ delivery.

Our recent multiple pregnancy complication cases

Some of our recent cases involving twins include:

  • £24 million lifetime compensation for a second twin with cerebral palsy from uterine hyperstimulation during induction of labour
  • Compensation of over £2.2million for a child with severe brain injury from TTTS caused by delayed referral to a fetal medicine centre
  • A settlement of nearly £3 million for a second twin with cerebral palsy who was deprived of oxygen when the umbilical cord became wrapped around his neck during delays at birth


They have a great deal of knowledge and expertise, and client care seems to be their top priority.

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