Overview

We all inherit 46 chromosomes, 23 chromosomes come from the mother, and the other 23 from the father during conception. There are 22 pairs of chromosomes called autosomes, which determine your general characteristics like hair and eye colour. There is one sex chromosome (X or Y), which determines your gender. However, in triploidy, there is a rare condition where there are three copies of each chromosome instead of two. This means there are a total of 69 chromosomes.¹ This causes life-threatening effects to foetuses whilst in the womb, and can lead to miscarriages or early death once born. Triploidy is a rare disorder that affects 1-3% of pregnancies. This article will explore what triploidy is and the long-term health effects for the infants that survive. 

Causes of triploidy

Triploidy is caused by having a full extra set of chromosomes. This usually happens when the egg becomes fertilised by two sperm, or the egg is fertilised by a sperm that has an extra set of chromosomes. The egg can also have an extra set of chromosomes and be fertilised by a normal sperm. This is not something that is inherited and passed through families and generations. It is also not linked to parents' ages. 

There are two types of triploidy. When the extra set of chromosomes is gained from the father, triploidy is referred to as diandric, and when it is taken from the mother, it is called digynic.² 

• Diandric: Causes the foetus to have delayed growth and an enlarged placenta, or the placenta does not grow normally
• Digynic: Where the foetus has a very delayed growth and uneven growth of body parts

This is important to know when considering the type of pregnancy seen. A molar pregnancy is where there is an abnormal growth of cells called trophoblasts. This group of cells becomes responsible for feeding the growing foetus, which is referred to as the placenta. There are two types of molar pregnancies: complete and partial molar pregnancies. Partial molar pregnancies are linked to diandric pregnancies, where the father contributes to having an extra set of chromosomes. It’s not usually seen when the chromosomes are passed down from the mother.³

Impact of triploidy on foetal development

• Severe restriction of growth in the uterus due to impaired placental function, which means there’s less oxygen and nutrients going to the baby, meaning organs do not grow properly 
• The brain doesn’t divide into two hemispheres, causing facial deformities (holoprosencephaly); there may be large fluid-filled areas, and the brain and skull remain abnormally small (microcephaly), causing intellectual and neurological deficits 
• Development of cleft lip
• Wide eyes (hypertelorism) or small eyes (microphthalmia)
• Abnormal development of the ears
• Impaired heart function due to incomplete development, or holes in the walls of the heart, meaning cannot flow normally between the chambers of the heart (septal defects)
• Development of extra toes and fingers(polydactyl) 
• Shortened limbs
• Clubfoot, where the feet are twisted into an abnormal position 
• Incomplete formation of the spine
• Underdeveloped lungs, making breathing harder or nearly impossible
• Kidneys are larger than normal or underdeveloped, causing low amniotic fluid levels
• Intestines can grow outside the body

Triploidy affects many areas of foetal development, causing severe abnormalities in the way the brain, heart and limbs develop. The limited growth and problems with the placenta make it extremely difficult for the baby to grow normally, compromising survival.⁴ 

Long-term health implications of triploidy 

Triploidy is a severe disorder where infant survival is very rare. It causes abnormal growth in nearly every organ. As the survival rate is very poor, long-term health effects are not always seen. There are rare cases where the foetus survives, but it is only for a short while, as they have fatal complications. These complications can include heart problems, neurological deficits, growth and developmental delays, poor metabolism, and breathing and digestion issues.⁵

Neurological impacts

Triploidy stops the brain from growing normally, causing the following:

• Developmental delays: Skills like sitting up and crawling would be delayed and may not be possible due to poor muscle control and abnormal brain growth
• Seizures: Babies that survive tend to have recurring seizures as electrical activity in the brain cannot be controlled and maintained, which can cause further brain damage
• Intellectual disabilities: Little to no cognitive function is normally seen, making learning new things, communicating with others and the world around them nearly impossible⁵

Cardiovascular effects

During development in the womb, the heart does not grow to its full capacity, causing heart problems such as:

• Long-term heart failure: Involves poor circulation and less oxygen being delivered, meaning organs cannot function normally
• Congenital heart defects: There may be valves that have not formed properly, holes in the heart, and/or underdeveloped chambers⁵

Growth and development

There is usually intrauterine growth restriction (IUGR), meaning the babies cannot grow to full size and are much smaller than normal. They may have:

• They may struggle with sucking and swallowing, and as a result, they may need to be fed by a tube
• Weight and height would be largely under what is considered normal
• They may be unable to sit up and walk, or this could be very delayed⁵

Endocrine effects

The endocrine system is made up of hormones that help to promote growth and metabolism. However, in triploidy, these hormones are not balanced, causing:

• Metabolic disorders: Nutrients cannot be processed normally, meaning there are difficulties in gaining weight, excessive tiredness and troubles maintaining normal body temperature
• Hormone levels are not maintained: Different glands do not function normally, resulting in stunted growth, blood sugar levels not being maintained, and low energy levels⁵

Gastrointestinal and respiratory impacts

Babies born after surviving triploidy usually have poor lung and digestive function, causing:

• Babies may have reflux, vomiting and poor digestion, making weight gain very difficult 
• Swallowing may be difficult due to structural changes in the throat
• Lungs become weak, making it hard to breathe normally and may require a ventilator to provide support for breathing⁵

Weakened immune system

Triploidy weakens the immune system, putting the infant at risk of developing infections like pneumonia and sepsis. This is because the body is unable to make white blood cells and antibodies, which fight off infections.⁵

Palliative care and supportive care

Babies that survive through the pregnancy tend to live for a couple of hours, and possibly days. As there is no cure, the focus is on making the baby as comfortable as possible through palliative care. Medical intervention is focused on providing:

• Support breathing by offering oxygen therapy, but ventilators are not used as the lungs are too underdeveloped to work long-term
• Reduce pain through medication
• Help with nutrition by giving small amounts of milk
• Provide comfort by extending skin-to-skin contact

Medical intervention is not usually recommended as the majority of the organs are too underdeveloped, and even with intervention, the babies will not survive long-term. Trying to extend life may cause more suffering and reduce the quality of life. This is why palliative care and support are recommended to help provide comfort until passing.⁶

Psychological impact on families

A triploidy diagnosis is devastating and can cause intense emotional distress for parents and families. 

Grief and loss 

Parents grieve not only for their baby but also for the future they imagined. The loss is deep, even if the baby was only carried for a short time.

Guilt and self-blame 

Many parents wonder if they did something wrong to cause triploidy, but it’s important to know that triploidy happens randomly and is not caused by anything a parent did or didn’t do.

Anxiety and depression

The emotional toll of losing a baby can lead to ongoing mental health struggles, making professional support essential.

Strain on relationships

Couples may grieve in different ways, leading to communication challenges and emotional distance. Support from loved ones and counselling can help families cope together.

Because the grief of pregnancy loss is often not fully recognised by society, parents may feel isolated. Support groups, therapy, and talking with others who have experienced similar losses can be incredibly helpful.

Summary

Triploidy is a rare condition with 69 chromosomes. Surviving infants face severe, life-limiting health problems affecting nearly all organs, including major neurological, cardiovascular, and growth issues. Life expectancy is very short, with palliative care focused on comfort due to the severity of these complications.