With one in every 65 pregnancies resulting in a multiple birth, it’s not a given that just because there are no twins in your family, you won’t have them. Debbie Ross from the Twins and Multiple Births Association says, “The older a mum you are, the more likely you are to have twins, and also if you’ve had twins before. Fertility treatment and IVF also increases the likelihood, as more than one embryo is implanted into the womb.”


So whether you suspect it’s going to be you, or you already know, here’s the what, why and how of having more than one.

It is possible to have twins by different fathers

How did that happen?!

Twins are formed pretty much at the moment of conception, when, or just after, the egg and sperm meet.

  • Identical twins develop when a fertilised egg splits in two.
  • Non-identical twins result from two separate eggs being fertilised by two sperm at the same time.
  • For triplets, quads, and so on, it’s the same process with one or more egg being fertilised.
A healthy weight gain in pregnancy is important - being too underweight or overweight when pregnant comes with risks.

When will I find out I’m having multiples?

You might have a suspicion beforehand, but most mums find out at the 12-week scan. “The symptoms of pregnancy can be magnified, such as rapid weight gain, morning sickness and fatigue,” says Delyth Raffell, founder of TwinsUK.

Can you tell the difference?

How can I find out if they’re identical?

The test for ‘identicalness’ is officially called zygosity determination. An ultrasound at 10-14 weeks might confirm identical twins. Or at birth, an examination of the placenta can reveal the zygosity. “Identical twins share 100% of their DNA and a simple test using a swab from their cheek cells has 99.99% reliability,” says Delyth. Zygosity testing isn’t routine, so if your hospital doesn’t do it, you can pay for a private test that costs around £80.

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Are twins born smaller?

For the first 26 weeks your twins will develop at exactly the same rate as a single baby, although they may be smaller. Twins often start out at different sizes and grow at different rates to each other. It’s only a problem if they start off the same size and one suddenly starts to develop more slowly. If so, you’ll be scanned more frequently and, depending on the health of you and your twins, they may be delivered early.

Angie was shocked to find out her two babies were at slightly different developmental stages

Is there enough room?

Your womb is incredibly stretchy and the average weight for twins is 5.5lbs each, so it’s not a huge problem! Also, twin pregnancies are considered full term at about 38 weeks, rather than the usual 40. “Due to the cramped space within the uterus, and possible unequal sharing of maternal nutrition, there can be slight developmental or physical differences between the babies,” says Delyth.

Will I be twice the size?

Well your bump will be, so you’ll gain more weight than with one. You’ll start to show earlier with twins – at about 11 weeks rather than 13. As well as the weight of the babies, you’ll be carrying twice the usual amniotic fluid, plus a larger placenta (or even two). You’ll also need to take in more calories (around 600 a day) in the last trimester.

Will I have more morning sickness?

It’s likely, yes, and it’s all to do with your hormones. Qualified Midwife and founder of www.havingtwins.co.uk, Penny Price explains, “Women who have twins have an increased amount of the hormone HCG, which often (but not always) causes increased morning sickness.” HCG is essential for a healthy pregnancy, so it’s nothing to worry about.

However you feed your twins, rest assured you’re giving your babies a great start in life

Are there more risks?

The biggest risk with a twin or multiple pregnancy is premature labour. Other conditions that pose a risk to mums with multiples include anaemia, hydramnios (excess amniotic fluid), vaginal bleeding (minor bleeding or miscarriage), gestational diabetes and pre-eclampsia. You’ll have extra tests and scans to make sure everything’s ok.

“But, while you should be aware of the risks, most women sail through their twin pregnancy without many complications,” says Delyth Raffell.

You are likely to see an obstetrician if you are booked in for a hospital delivery.

Will I get special care?

Because of the higher risk levels, you’ll be referred to a consultant for your antenatal care and usually you’ll get monthly check ups. If your babies share an amniotic sac, you’ll have more scans because of the increased risk of twin-to-twin transfusion syndrome. This is rare, but sometimes, when twins share a chorion (the outside layer of the amniotic sac), blood can pass from one twin to the other at birth, which can be risky.

Knowing what to expect when it comes to a caesarean birth will

Will I need a caesarean?

“It depends largely on the position of the babies,” says Delyth. “If both are breach or transverse (lying across the uterus), you’re more likely to have a caesarean.” You might also be offered one if your twins are identical, as that increases the risk of twin-to-twin transfusion syndrome. “Be guided by your obstetrician as it’s not a given that you have to have a caesarean,” advises Penny Price.

Mums’ stories

“We had two embryos implanted through IVF, but one divided after the transfer and we ended up with triplets! We were very surprised but so delighted – it felt like winning the lottery. It was our sixth try at IVF so to have a whole family in one go was, sorry to use a cliché, a dream come true.”

Barbara Hepburn, 39, from New Zealand, mum to triplets Rosanna, Estella and Otis, 7 months

“As soon as they found out the boys were identical, I was closely monitored to make sure they didn’t get twin-to-twin transfusion syndrome. I had monthly consultant appointments and saw the midwife regularly too. I had scans every fortnight, which, while time consuming, was really reassuring.”

Leanne Williams, 28, from Calne, Wiltshire, mum to identical twins Charlie and Freddie, 4 1/2 months


  • A third of twins are identical, two thirds are non-identical
  • Twins have been known to develop their own language
  • There are at least 125 million living multiples worldwide
  • Identical twins have almost identical brain wave patterns

Read more…