Identical triplets

Although it may seem to be almost impossible, conceiving with identical triplets, whilst quite rare, is actually possible.

There is no one, consistent statistic quoted when it comes to the odds of having identical triplets. But the generally agreed upon figures are in the vicinity of between one in 60 thousand to one in 200 million. So it is clear that there is no consensus on the likelihood and even the experts cannot agree. This may be because there is thought to be a natural attrition to the numbers of identical triplets who continue to develop towards birth. Alternately the true figures just cannot be accounted for.

But what exactly are the odds of having identical triplets?

Non identical triplets occur around once in every 4000 naturally conceived pregnancies. Just for some added confusion, the chances of having identical triplets are about one in every six (overall) triplet pregnancies.

How are identical triplets formed?

The majority of triplets are what is known as trizygotic. This is because they are formed when three separate, individual eggs are fertilised by three separate sperm. These babies share the same characteristics as any other siblings with the same biological parents. They can be the same or opposite genders.

Triplets can also occur when two of the babies are identical and have formed from monozygotic (identical) twins – see below. This means the other, third baby is a singleton, formed from a completely separate egg and sperm. Two of the babies will be identical but the third will be their own, unique little individual.

But are all three identical triplets exactly the same?

When one single egg is fertilised by one single sperm and this fertilised zygote quickly and evenly divides into three separate zygotes, identical triplets are formed. Another possibility is that the fertilised egg splits into two and then one of these eggs divides again. These are what are known formally as monozygotic triplets. This splitting occurs shortly after fertilisation and before a woman even suspects she is pregnant. There is nothing she or her partner can do to influence the likelihood of this occurring. It is pure biological luck.

Even taking fertility hormones such as Clomid will not influence the likelihood of conceiving with identical triplets. Although artificial hormones do increase the number of eggs matured to ovulation each month, Clomid does not cause splitting of the fertilised egg after fertilisation.

Although it is extremely unlikely, it is still possible for identical triplets to occur after single embryo transfer which occurs during fertility assistance. This did happen to one woman in 2008 (the first recorded event) who was undertaking fertility treatment. One single embryo split after being returned to her uterus and then divided three times, resulting in three identical boys.

When identical triplets are formed this means that all three share the same identical DNA, gender, characteristics and features. Some researchers believe that a certain percentage of monozygotic triplets actually start as identical quadruplets but one of the embryos does not continue to grow to maturity or becomes reabsorbed. (See Vanishing Twin Syndrome).

How would I know if I’m having identical triplets?

You won’t in the early stages of your pregnancy. But you could suspect you are having a multiple pregnancy because of your exaggerated pregnancy symptoms. Extreme nausea, having an obvious pregnancy belly much earlier than expected or being unable to hold even the smallest volume of wee in your bladder may all raise your suspicions.

Triplet pregnancy is confirmed by ultrasound and this can be done in the first trimester of pregnancy, based on pregnancy symptoms. It may not be clear in the very early stages of pregnancy if the triplets are identical or not. If they share a placenta, this is a strong and definitive sign that they are identical. However, it can be very difficult to determine via ultrasound the exact placental structure. Separate placentas can also fuse making them appear to be one.

When a triplet pregnancy is confirmed, it is standard obstetric practice for a woman to require more frequent ante natal checks, ultrasounds, pathology work and general health checks. Bed rest may be ordered if there is a threat of miscarriage or premature labour. If a mother is pregnant with triplets and she does not have enough “in home” support, she may need to be hospitalised as an enforced form of bed rest. Some women who are pregnant with multiple babies need to spend many months in hospital, especially if they are threatening to miscarry and their pregnancy is at risk.

How can you tell identical triplets apart?

Well this can be tricky. Even parents of identical triplets say they can get confused about which baby is which. This is why many have developed little tricks to help tell their babies apart and not get them confused with each other.

One of the more popular strategies is to paint one little fingernail of each baby with a different colour nail polish. Different coloured clothing on each e.g. white/lemon/pale green; white/pink/blue are also good prompts to differentiate three tiny identical babies. Some parents retain their triplets hospital arm bands long after they could be removed and only take them off when they become too tight on their babies growing arms.

Each baby is likely to display their own unique and special characteristics from the newborn stage. Parents are often keen to appreciate the individual differences between their three babies and see them as separate rather than “the triplets”. With time and maturity, triplets, just like singletons exert their own, unique personalities.

What are the risks to a mother in carrying identical triplets?

Overall, the metabolic stress to her body of carrying triplets is considerable and as the pregnancy advances, the stress and risks increase.

There is an increased risk of every pregnancy complication including:

• Hypertension and Preeclampsia.
• Placenta Praevia.
• Premature Labour and delivery.
• Ante Partum Haemorrhage.
• Post Partum Haemorrhage.
• Gestational Diabetes.
• Caesarean section delivery is most likely. Because of this there are the associated risks of any abdominal surgery including bleeding, infection, delayed healing and pain.

Average Pregnancy Weight Gain with Triplets

NB Any rapid gain or loss of weight is concerning, especially in the third trimester of pregnancy. Monitoring weight is just one way of assessing maternal/foetal well being and should not be considered in isolation of other observations.

What are the risks to the identical triplets?

• Higher incidence of congenital abnormalities.
• Prematurity – statistically, the majority of triplets are born before 34 weeks of gestation.
• Low birth weight – the average birth weight for an individual triplet is around 1.8 kilos.
• Breathing and circulation difficulties due to underdeveloped lungs and immature respiratory function.
• Higher risk of infection.
• Transfusion Syndrome between the triplets.
• Cerebral Palsy.
• Global delays including social/Emotional, Communication, Fine Motor and Cognition and Gross Motor.

For more information:

• The Australian Multiple Birth Association. (Each State and/or Territory has their own branches).
• Multiples NZ
• Multiple Birth Parents
• HealthInsite