Risks Associated with Carrying Multiples (Twins or More)

With all pregnancies there are associated risks. There are various factors that can increase the chances of problems during pregnancy, and carrying more than one baby is one of them. It is important that you are aware of these risks and of how to minimise them, but at the same time you must not let your pregnancy be dominated by the fear that something will go wrong. An optimistic outlook is beneficial to both your health and the health of your babies.

Am I at greater risk of suffering a miscarriage if have twins?

In short, yes, multiple pregnancies do have a higher rate of miscarriage than single pregnancies. Identical twins are thought to be at greater risk than fraternal twins. As with single pregnancies, though, the majority of these occur during the first trimester, before the mother is even aware that she is carrying twins. Consequently, there are no solid figures to indicate the actual increased risk for multiples.

It is possible to miscarry one of the foetuses while continuing with a healthy pregnancy for the remaining foetus (or foetuses). If this happens before the mother has had a scan then it is possible that she might believe that she is no longer pregnant when, in fact, she is still carrying one or more healthy foetus. Sometimes, if only one twin is miscarried, the mother might experience very few or even no symptoms at all. The twin is absorbed back into the mother's body and she might remain unaware that she ever carried more than one foetus in the first place - this is what is known as 'vanishing twin' syndrome.

Increased risks to your health

As many as 25% of multiple pregnancies are affected by problems associated with high blood pressure. When you are carrying multiples you are automatically expected to attend more frequent antenatal appointments. At all of these your blood pressure will be monitored.

Pre-eclampsia occurs more frequently in mothers expecting multiples. Significant amounts of protein in your urine or elevated blood pressure are the most recognisable symptoms of pre-eclampsia and your midwife will check these at all of your antenatal appointments.

You are also up to 3 times more likely to have gestational diabetes if you are pregnant with multiples. You should let your midwife know if you are very thirsty a lot of the time, if you urinate often or if you are feeling particularly tired. Unfortunately all of these symptoms are also common symptoms of a healthy pregnancy so they are not clear indicators. However, if your midwife is concerned then he or she will arrange for you to have a glucose intolerance test.

There are also risks associated with the delivery of multiple babies; this is because you are more likely to experience a haemorrhage, early labour or need a caesarean section.

Increased risk to the babies' health

Premature birth is common amongst multiples. Your ultrasound scans will provide an estimated due date for your baby as week 40, but generally multiple births aren't expected to go further than 35-57 weeks. Half of all twins, and 90% of triplets are born before 37 weeks and have a birth weight of below 2.5kg (5.5lb). Low birth-weight multiples tend to be have fewer health problems than single babies born at the same weight.

Premature birth of multiples has an increased risk of death in the early days after birth. Twins and triplets are also more likely to have birth defects or illnesses, especially cerebral palsy.

Identical twins that share a placenta (monochorionic) have a 10-15% risk of a condition known as Twin-Twin Transfusion Syndrome (TTTS). Abnormal connecting blood vessels in the placenta cause an imbalance in blood flow from one twin to another. Foetal death is higher amongst babies with this condition if it is untreated, but your antenatal team will discuss your treatment options with you.