At least 50-60 per cent of twins are born before 37 weeks, and up to fifteen per cent before 32 weeks. Once the babies are born, each baby will be assessed and treated individually.
Two key factors in how a baby does after a premature birth are gestational age and birth weight. In addition, some babies have other health problems, identifiable before birth or soon after, that may affect their progress and outcome.
The more premature a baby is, the more assistance they are likely to require. For example, twins born at 36 weeks may be more mature but are still likely to be a little slow in learning to breastfeed; those born before 32 weeks are likely to require assistance with breathing (ventilation) and may have other health problems (temporary or otherwise); and those born before 28 weeks may have potentially life-threatening problems at birth and a poorer long-term prognosis. However, if a premature baby has a good weight for gestational age at birth, their chances of survival, and of a life with minor or no permanent health problems, improve considerably. The issue of prematurity is therefore not the only factor to take into consideration when babies are born early.
Reasons for premature delivery
There are several reasons why so many twins are born prematurely. One is that the mother goes into labour spontaneously. We still do not know what triggers labour, or why membranes rupture without warning, and it is therefore very difficult to prevent premature labour from occurring. Sometimes, if there are concerns about the health of the mother or the babies, the decision is taken to deliver the babies early (whether by induction or Caesarean section), as the risks to the babies by being born at this time are less than if they remain for longer in the womb.
The reasons for early delivery include:
- risk of infection after premature rupture of the membranes
- pre-eclampsia or high blood pressure
- pre-existing diabetes or gestational diabetes
- genital tract infection (e.g. chlamydia, gonorrhea)
- bleeding from the placenta due to placenta praevia or placental abruption
- reduced efficiency of the placenta
- intra-uterine growth restriction (IUGR)
- monochorionic pregnancy
- twin-to-twin transfusion syndrome (TTTS)
- fetal abnormality.
It is not possible to predict if a woman with a healthy pregnancy will go into spontaneous premature labour (although it is known that if you have had a previous, unexplained premature birth it is more likely to happen again). Similarly, there are often no indicators that an issue will develop that requires an early delivery. No medication given to women with twins to prevent pre-term delivery has been shown to have an improved outcome.
What happens when you go into labour prematurely
If you think you might be experiencing signs of premature labour, call the labour ward without delay, whatever your gestation, so that they can advise you on what to do. Similarly, if you have any bleeding you must seek advice immediately.
If you are asked to come in to the hospital to be examined and it is confirmed that your labour is beginning, you may be given a drug to relax the uterus; this, together with complete bed rest for a few days, may slow down the contractions or stop them altogether. If your contractions do not cease, the doctors will have a discussion with you and a decision will be made whether to deliver the babies vaginally or by Caesarean section.
Depending on the gestation of your pregnancy, doctors may attempt to delay the delivery for as long as possible, as the more time that very premature babies are in the womb, the more it helps their lungs and brains to mature. Doctors will give you a steroid injection (or two, twelve hours apart), which speeds up the production of surfactant, the substance that is essential for the functioning of the lungs.
Surfactant only begins to be produced at 26 weeks, continuing right up until 40 weeks. So the later babies are born, the better their lung development will be, which increases their chances of being able to breathe unassisted at birth. Delaying the delivery may also enable you to be transferred, if necessary, to a hospital with suitable neonatal care facilities. This will mean that you and your babies are both in the same hospital after the delivery and, if they are very premature, will ensure they are given the appropriate level of care from the moment they are born.
Excerpt from Expecting Twins? by Professor Mark Kilby, Jane Denton and Debbie Beckerman, published by Hardie Grant Books, $34.95.