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Are you carrying twins?
You might think you're carrying more than 1 baby if:
It's usually possible to find out if you're having twins through your 12-week scan.
At the scan, you should be told whether the babies share a placenta (meaning they're identical) or if they have 2 separate placentas (meaning they can be identical or not).
If this is not clear from the first scan, you should be offered another one.
What causes twins?
Nobody knows what causes identical (monozygotic) twins. Everyone has the same chance of having identical twins: about 1 in 250.
Identical twins do not run in families. But there are some factors that make having non-identical twins more likely:
- non-identical twins are more common in some ethnic groups, with the highest rate among Nigerians and the lowest among Japanese
- if you’re pregnant and over 35 you’re more likely to have non-identical twins because you’re more likely to release more than 1 egg during ovulation
- non-identical twins run on the mother's side of the family, probably because of an inherited tendency to release more than 1 egg
IVF can increase the chance of twins, as more than 1 embryo may be transferred.
It's important to understand your birth options if you're expecting more than 1 baby.
Your birth choices with twins
It's a good idea to discuss your birth options with your midwife or consultant early on in your pregnancy.
You'll normally be advised to give birth in a hospital, as there's a higher chance of complications with twins.
There are usually more health professionals at a multiple birth – for example, there may be 2 midwives, an obstetrician and 2 paediatricians (1 for each baby).
For more information on who's who, read about the antenatal team.
The process of labour is more or less the same as for 1 baby, but your maternity team will usually advise you to have your babies electronically monitored because of the higher risk of complications.
This means attaching belts with sensors (1 for each twin) to your bump. You'll still be able to move around into different positions.
Once your waters have broken, your midwife may ask your permission to attach a clip attached to a wire to the first baby's head to get a more accurate measure of their heartbeat.
You'll be offered a drip in case it's needed later – for example, to restart contractions after your first baby is born.
Triplets or more babies are almost always delivered by a planned caesarean section.
Can you have a natural birth with twins?
Lots of women think they have to have a caesarean section with twins, but in fact, many twin births are vaginal
If you're planning a vaginal delivery, it's usually recommended that you have an epidural for pain relief, but you can discuss this with your midwife.
If there are any problems, it's easier for your antenatal team to deliver your babies quickly if you have already got an epidural in place.
You're more likely to have a vaginal birth if the first twin is in a head-down position.
But there may be medical reasons why a vaginal birth is not recommended.
If you have had a caesarean section before, for example, it's not usually recommended that you have a vaginal birth with twins.
As with any vaginal birth, you may need an assisted birth. This is where forceps or vacuum delivery are used to help deliver your babies.
Once the first baby is born, your midwife or doctor can check the position of the second baby by feeling your tummy and doing a vaginal examination. They may also use an ultrasound scan.
If the second baby is in a good position, it should be born soon after the first, as your cervix is already fully dilated.
If your contractions stop after the first baby is born, the doctor or midwife may discuss giving you hormones via a drip to restart them.
Caesarean section and twins
In the UK, more than half of twins and almost all triplets are delivered by caesarean section is a common method used during twin and triplet births.
You may choose to have a planned caesarean, or your doctor may recommend a caesarean, if:
- the first baby is lying feet, knees or buttocks first (breech)
- 1 twin is lying sideways (transverse)
- you have a low-lying placenta
- your twins share a placenta
- you have had a difficult delivery with a single baby before
As with any pregnancy, if you plan a vaginal birth, you may still end up needing an emergency caesarean.
In a small number of cases, some women deliver 1 twin vaginally and then need a caesarean section to deliver the second twin.
When you're expecting twins or triplets, it's important that you attend all your appointments because of the increased risks with this type of pregnancy.
Your antenatal team should be experienced in caring for women having twins or triplets.
Check-ups and scans in a twin pregnancy
The number of tests and scans you'll be offered will depend on the type of twins or triplets you're having.
Women with multiple pregnancies should be offered an ultrasound scan at around 11 to 14 weeks. It's important to attend this appointment.
This is the best time to find out what type of placenta and membranes your twins have (chorionicity) and check your dates.
You can also have a nuchal translucency test for Down's syndrome done at the same time if you wish.
You'll also be offered a scan, called an anomaly scan, at 20 weeks to check that your babies are developing normally.
Different types of twins
One-third of all twins will be identical and two-thirds non-identical.
Identical (monozygotic) twins happen when a single egg (zygote) is fertilised.
The egg then divides in 2, creating identical twins who share the same genes.
Identical twins are always the same sex, so if your twins are identical, you'll have 2 girls or 2 boys.
Non-identical (dizygotic) twins happen when 2 separate eggs are fertilised and then implant into the womb (uterus).
These non-identical twins are no more alike than any other 2 siblings.
Non-identical twins are more common. The babies may be of the same sex or different sexes.
How can I tell if my twins are identical?
The most accurate way to tell if twins are identical is through a DNA test. This can only be done after your babies are born.
The placenta could also provide clues. If your first ultrasound scan is done before 14 weeks, it should be possible to tell accurately what kind of placenta your twins have.
Otherwise, the placenta can be examined after your babies are born.
For more information on this and birth options, read about giving birth to twins or more.
Read more about the different types of twins on the Twins Trust website.
More detailed information on DNA testing and how to find out whether twins or triplets are identical is available on the Multiple Births Foundation website.
What extra care may I need?
If your babies are MCDA, you can expect more scans and monitoring, as this type of twins has the highest risk of twin-twin transfusion syndrome (TTTS), which is an abnormality of the placenta.
You may be referred to a regional centre for foetal medicine to be seen by a specialist doctor.
If your babies are MCMA, you'll also have frequent scans. With this type of twins there's often some cord entanglement, which can cause complications.
These types of twins are rare, and you can expect to receive specialist care and close monitoring.
If your babies are DCDA, the risks to their health in the womb are much lower. You'll usually be scanned every 4 weeks.
It's important to attend all your appointments so any problems can be picked up early and treated if necessary.
Risks in twin pregnancies
While most multiple pregnancies are healthy and result in healthy babies, there are more risks to be aware of when you're pregnant with 2 or more babies.
Make sure you go to all your antenatal appointments so any problems can be picked up early and treated if necessary.
Twins and triplets have a higher risk of being born prematurely (before 37 weeks) and having a low birthweight.
Most twins and triplets are born prematurely.
Around 6 in 10 twins are born before 37 weeks. Almost 8 in 10 triplets are born before 35 weeks.
If you are expecting twins or triplets, you will be offered a planned birth at:
- 37 weeks for twins with a placenta each
- 36 weeks for identical twins sharing a placenta
- 35 weeks for an uncomplicated triplet pregnancy
- 32-33 weeks for MCMA twins
It can be dangerous for twin and triplet pregnancies to carry on after the planned birth dates. Plans for the birth will be discussed with you taking into account your needs and preferences.
If you turn down the offer of a planned birth, you will be offered weekly appointments with an obstetrician and weekly ultrasound scans plus a foetal growth scan every 2 weeks.
Your obstetric team will work closely with you throughout your pregnancy and after your babies are born to help make sure you and your babies are safe and healthy.
Twin-twin transfusion syndrome
Twin-twin transfusion syndrome (TTTS) affects identical twins who share a placenta (monochorionic).
The risk is higher for MCDA twins, but it can happen in MCMA twins, too.
It's caused by abnormal connecting blood vessels in the twins' placenta.
This results in an imbalanced blood flow from 1 twin (known as the donor) to the other (recipient), leaving 1 baby with a greater blood volume than the other.
TTTS affects 10 to 15% of monochorionic twins and can have serious consequences.
You'll need to discuss your individual case with a doctor, as what works in one TTTS pregnancy may not be appropriate in another.