Multiple pregnancy: twins or more

A multiple pregnancy means you are carrying two or more babies. Two babies are called twins, three are triplets, and four are quadruplets.

Most multiple pregnancies result in healthy babies. However, they need closer monitoring because some complications are more common than in a pregnancy with one baby. The most common is premature birth, meaning birth before 37 weeks.

Twins are described by whether they share a placenta and amniotic sac. The placenta supplies oxygen and nutrients. The amniotic sac is the fluid-filled membrane around a baby.

The main types are:

• Dichorionic diamniotic twins: each baby has a separate placenta and sac
• Monochorionic diamniotic twins: the babies share a placenta but have separate sacs
• Monochorionic monoamniotic twins: the babies share both a placenta and a sac

These terms may be shortened to DCDA, MCDA and MCMA. Triplets can also have different combinations of shared or separate placentas and sacs.

Knowing this arrangement is important. Babies who share a placenta or sac need more frequent ultrasound scans because they have specific risks.

There is no symptom that reliably confirms a multiple pregnancy. An ultrasound scan is needed.

Pregnancy symptoms may begin earlier or feel stronger because the body produces higher levels of pregnancy hormones. You may experience:

• Nausea or vomiting
• Marked tiredness
• Breast tenderness
• Faster abdominal growth
• Pelvic pressure or back discomfort
• Heartburn, constipation or breathlessness later in pregnancy

These symptoms can also occur in a pregnancy with one baby. The size of your abdomen does not show how many babies you are carrying.

Persistent vomiting can cause dehydration and weight loss. This is called hyperemesis gravidarum and may require treatment.

Later in pregnancy, you should usually notice movements from each baby, although it may be difficult to tell which baby is moving. Your maternity team can explain how to monitor your babies’ usual pattern of movement.

Multiple pregnancy happens in two main ways.

Non-identical twins develop when two separate eggs are fertilised. Each baby has different genetic material, like any other siblings. They may be the same or different sexes and usually have separate placentas and sacs. Their placentas can sometimes appear joined on a scan.

Identical twins usually develop when one fertilised egg splits into two embryos. They have very similar genetic material and are usually the same sex. Whether they share a placenta or sac is linked to when the embryo divided.

It is not always possible to explain why an embryo splits.

Factors associated with non-identical twins include:

• Fertility treatment that stimulates the release of more than one egg
• Transfer of more than one embryo during in vitro fertilisation, or IVF
• A personal or maternal family history of non-identical twins
• Increasing maternal age, because releasing more than one egg becomes more likely

Identical twinning is generally not inherited. Having twins in the father’s family does not directly increase the pregnant partner’s chance of releasing two eggs.

Multiple pregnancy is confirmed by ultrasound. It may be found during an early scan or at the routine dating scan.

The scan checks:

• The number of babies
• Whether the babies share a placenta or amniotic sac
• Each baby’s heartbeat and early development
• The estimated stage of pregnancy
• Whether there are signs of an early complication

Identifying the placenta and sac arrangement is called determining chorionicity and amnionicity. This is most accurate early in pregnancy and guides the timing of later scans.

You will usually be offered additional ultrasound scans to monitor growth and amniotic fluid. Babies sharing a placenta generally need scans more often than babies with separate placentas.

Screening for chromosomal conditions, such as Down syndrome, can be more complex in a multiple pregnancy. Your maternity team can explain which blood tests, ultrasound tests and diagnostic tests are available and what their results can show.

A multiple pregnancy is managed with additional antenatal care rather than a treatment that removes the condition. Care is usually coordinated by a team experienced in twin or triplet pregnancies.

Appointments may include blood pressure checks, urine tests and blood tests. Ultrasound scans monitor each baby’s growth, fluid levels and blood flow. The exact schedule is based mainly on how many babies there are and whether they share a placenta.

Healthy eating is important, but carrying twins or triplets does not mean you need to eat twice or three times as much. Your care team can advise about suitable weight gain and pregnancy supplements. Iron may be recommended if blood tests show anaemia, meaning too few healthy red blood cells.

Low-dose aspirin may be advised when your overall risk of pre-eclampsia is increased. Pre-eclampsia is a pregnancy complication involving raised blood pressure and sometimes organ problems. Whether aspirin is appropriate is based on your medical history and local guidance.

There is no routine treatment that prevents every premature birth in a multiple pregnancy. If early birth becomes likely, you may be offered medicines to help prepare the babies, depending on the stage of pregnancy and the clinical situation.

Birth is usually planned earlier than it would be for one baby. The timing depends on the number of babies, their placenta and sac arrangement, growth, position and any complications.

A vaginal birth may be possible, especially when the first twin is head-down and there are no other concerns. A caesarean birth may be recommended if the first baby is not head-down, the babies share one sac, there are three or more babies, or another complication makes surgery safer. Plans may change during labour.

Complications are more common in multiple pregnancy, but they do not affect everyone.

Premature birth is the main concern. Babies born early may need care in a neonatal unit for help with breathing, feeding or keeping warm. The chance of early birth rises with three or more babies.

The babies may grow at different rates. One may be smaller because the placenta is not supplying it as effectively. Ultrasound scans help identify this.

Babies who share a placenta can develop complications involving uneven blood flow. Twin-to-twin transfusion syndrome, or TTTS, happens when blood passes unevenly between the babies through shared placental blood vessels. It can affect both babies and needs prompt specialist assessment. Other shared-placenta complications include twin anaemia-polycythaemia sequence, known as TAPS, and selective fetal growth restriction.

Twins sharing one amniotic sac have a risk of their umbilical cords becoming entangled. These pregnancies receive particularly close specialist monitoring.

For the pregnant person, possible complications include:

• Anaemia
• High blood pressure and pre-eclampsia
• Gestational diabetes
• Severe nausea and vomiting
• Blood clots
• Heavier bleeding after birth
• Assisted vaginal birth or caesarean birth

Recovery after birth can be affected by surgery, blood loss, premature delivery and the demands of caring for more than one newborn.

Most naturally occurring multiple pregnancies cannot be prevented. There is no established way to prevent an embryo from splitting into identical twins.

Some multiple pregnancies are associated with fertility treatment. When IVF is being considered, transferring one embryo at a time can reduce the chance of twins or triplets. The appropriate approach depends on factors such as age, embryo quality, previous treatment and the fertility service’s guidance.

Medicines that stimulate ovulation can cause more than one egg to be released. Monitoring during treatment helps estimate this risk, but it cannot remove it completely.

Once a multiple pregnancy has begun, care focuses on monitoring and managing risk rather than trying to make it a single pregnancy.

You are likely to have more appointments and scans than someone carrying one baby. This can offer reassurance but may also require extra travel, time away from work and childcare planning.

Physical discomfort often becomes more noticeable earlier. Rest breaks, gentle activity when comfortable and practical help with daily tasks may be useful. Bed rest is not routinely advised simply because you are carrying twins or triplets.

Your maternity team will usually discuss birth planning before the final weeks of pregnancy. This includes where to give birth, pain relief, vaginal or caesarean birth, and the possibility of neonatal care. A hospital with suitable maternity and newborn services may be recommended.

Some babies remain in hospital after the parent is discharged, particularly if they are premature. Neonatal teams can help you take part in feeding, skin-to-skin contact and day-to-day care.

Feeding twins or more can take time to establish. Breastfeeding, expressed milk, formula feeding or a combination may be used. Support from midwives, infant-feeding specialists and family can make the workload more manageable.

Over the following months and years, most families settle into routines that work for them. Children from a multiple pregnancy are individuals and may develop at different rates. Babies born early may have development assessed using their corrected age, which accounts for how many weeks early they were born.

Keep routine antenatal appointments even when you feel well. Contact your maternity team between appointments if you have concerns about symptoms, growth, medicines, emotional wellbeing or your birth plan.

Seek urgent maternity advice if:

• Your babies are moving less than usual or their movement pattern changes
• You have vaginal bleeding or fluid leaking from the vagina
• You develop regular contractions, period-like pain or unusual backache
• You have persistent vomiting and cannot keep fluids down
• You develop a severe headache, vision changes, sudden swelling or pain below the ribs
• You have fever or feel significantly unwell

Call emergency services for severe breathing difficulty, chest pain, fainting, a seizure, heavy bleeding, or severe and persistent abdominal pain.

Do not wait for the next routine appointment when movements decrease or signs of premature labour occur. Maternity services can assess you and the babies even if the symptoms turn out not to be caused by a serious problem.

Are twins always considered a high-risk pregnancy?

A twin pregnancy has higher chances of certain complications than a pregnancy with one baby, so it receives closer monitoring. “Higher risk” does not mean that a problem will happen. Many twin pregnancies progress without a major complication.

Can twins have different fathers?

It is biologically possible for two separate eggs released in the same cycle to be fertilised by sperm from different people, but this is very uncommon. Identical twins develop from one fertilised egg and therefore cannot have different biological fathers.

How can doctors tell if twins are identical?

Twins who are different sexes are non-identical. Twins who share a placenta are usually identical, but twins with separate placentas may be identical or non-identical. DNA testing after birth can give a clearer answer when needed.

Can I have a vaginal birth with twins?

Many people can, particularly when the first twin is head-down and there are no complications that make caesarean birth safer. Your babies’ positions, gestational age, health and placenta arrangement all affect the plan.

Will twins be born early?

Twins and triplets are more likely to be born before 37 weeks, either because labour begins or because earlier delivery is recommended. It is not possible to predict the exact birth date for an individual pregnancy.

Do twins need to be delivered on the same day?

They are usually born within a short time of each other during the same labour or caesarean birth. Rarely, in a very early birth and carefully selected circumstances, specialists may try to delay the birth of the remaining baby.