Multiple pregnancy

A multiple pregnancy is when there are two or more babies growing in a mother's womb at the same time. They may be either:

• Identical - looking exactly alike
• Fraternal – like usual siblings

If you're expecting multiple babies rest assured you'll be in good hands. Guidelines ensure you'll receive care from a specialist as well as special antenatal education and advice on monitoring your pregnancy.

Identical multiples

Identical multiples happen in 1 in every 285 births. Identical twins occur when a single egg fertilised by one sperm splits into two. If the egg splits again, it produces triplets, and so on. These types of multiples are identical because they have the same:

• Chromosomes
• Blood type
• Hair and eye colour
• Hand and footprints

Their lips can sometimes be a bit different, and height and size may be influenced by environmental factors.

Fraternal multiples

Fraternal multiples happen when more than one egg is released from a woman's ovary and each egg is fertilised by different sperm. The babies are just like normal siblings with different genes. They only share 50% of their DNA and just happen to share the womb and be born together. Fraternal multiples are more common than identical multiples.

Same mum, different dad

Sometimes, if two eggs are released in a single month and are fertilised by two different men, it can result in two babies born to the same mum, but different dads. These fraternal babies are genetically half-brothers or sisters, who share 25% of their DNA.

Strong bonds

According to a survey of parents of multiples, these children have a unique advantage in life by having a special bond with someone who is always there for them. Around 95% of parents described their children as 'best friends for life', taking care of each other and sharing a special understanding. This may extend to a 'language only they understand'. Bonding seems to start even in the womb. One study of twins showed they made intentional movements towards each other by the 14th week of pregnancy. Finally, a survey of adult multiples found they are almost twice as likely to rely on their brother or sister for emotional support compared to ordinary siblings.

Multiple births - what to expect?

To be safe, most women giving birth to multiples in the UK do so in a hospital setting. This is for you and your babies' safety, as the risk of heavy bleeding is more likely with multiple births. Plus, over half of multiples need special care after they're born. Your hospital will have its own policy on these types of births which may include:

• A caesarean section
• Induced labour

Your obstetrician will discuss options with you ahead of time and may recommend a date for your labour. This will also depend on whether your babies share a placenta (monochorionic) or have their own placentas (dichorionic). At the end of the day though, the choice of how and where to have your babies is still yours.

Reason: Fertility drugs

One of the common reasons for multiple births is fertility treatment. This may be given to you if you are having trouble getting pregnant. These drugs may be used along with in vitro fertilisation (IVF). They increase levels of certain hormones in your body, which helps your ovaries release more eggs. This can increase the chance of you becoming pregnant. These drugs have been safely used for many years but there may be side effects that include a higher chance of multiple births.

Reason: IVF

In vitro fertilisation (IVF) is when eggs are removed from your ovaries and fertilised with sperm in a laboratory. The fertilised egg is then placed back inside your womb to grow and develop. The procedure can be carried out using your partner's sperm or sperm from a donor. In the UK a maximum of two embryos can be transferred to women under 40, and a maximum of three embryos to women over 40. In some cases, this results in two or more babies.

Reason: Mum's age

In the UK in 2015, women over 45 were the most likely to have multiple births. In fact, 1 in 10 pregnancies in that age range resulted in multiples. Reasons include:

• Ageing eggs which are more likely to split once fertilised
• More older women undergoing IVF

Reason: Mum's height

Your height and weight may influence your likelihood of having a multiple birth. Mums who have multiples are an average of an inch taller than other mums, according to one small study. It's possible that a hormone that's present in greater amounts in taller women may be the reason. Insulin-like growth factor (IGF) may make a woman's ovaries release more eggs, but more research is needed to be certain.

Reason: Milk

One US study suggests that dairy may be linked to a higher chance of having multiple babies. Researchers found that women who drank more milk or milk products were more likely to have twins. Some scientists suggest dairy intake may prompt your body to make more IGF, which can stimulate the release of more eggs during your monthly cycle.

Complication: Premature births

Premature births are one of the most common complications linked with having multiples. A full-term baby is usually delivered at around 39 or 40 weeks, while being born prematurely means before 37 weeks. Babies born before 32 weeks are at an increased risk of long-term problems like hearing loss, vision problems, and even brain damage. This is why you will be cared for by a specialist and monitored throughout your pregnancy and birth.

Complication: Pre-eclampsia

This condition causes high blood pressure and other potentially serious problems. It's possible in any pregnancy, but you're at higher risk with a multiple pregnancy. The first sign may be a rise in blood pressure and symptoms like:

• Swelling of feet, ankles, face and hands
• Headaches
• Vision problems
• Pain below the ribs
• Nausea and vomiting

Seek medical help right away as this can be dangerous for you and your babies. The only cure is to deliver the babies, so you'll be monitored closely until your babies can be delivered. The condition goes away after the mother gives birth.

More health checks

If you're having more than one baby your doctors and medical team will keep a close eye on you throughout your pregnancy and birth. You'll have more than the standard 7-10 antenatal check-ups, and the two ultrasound scans, recommended for a single pregnancy. Make sure you attend all your appointments. This is because there's a higher risk of complications and earlier deliveries than with single babies. Don't worry though, your babies' growth and development will be closely monitored and you will be watched carefully for signs of early labour.

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