How untreated thyroid disorders can affect a baby's growth and development

Experts explain how delayed diagnosis of thyroid disorders during pregnancy can disrupt brain development, growth and vision, with effects that may surface long after birth

Pregnancy places extraordinary demands on a woman’s body, and the thyroid gland plays a far bigger role in this journey than many realise. From supporting early brain formation to regulating growth, thyroid hormones quietly shape a baby’s development long before birth. When thyroid disorders go undiagnosed or untreated during pregnancy, the consequences can extend long after birth, sometimes affecting a child’s learning ability, growth patterns and even vision.

 

Doctors warn that while thyroid disorders are common and often manageable, delayed detection can turn a preventable condition into a lifelong challenge for the child.

 

How thyroid hormones support early foetal growth

 

Thyroid hormones are essential for the development of the baby’s brain and nervous system, especially in the first trimester. During this period, the foetus relies entirely on the mother’s thyroid hormone supply.

 

 

“Thyroid hormones are vital for the baby’s brain and nervous system development, particularly during the first trimester when the baby is solely dependent on the mother’s thyroid hormone levels,” explains Dr Astha Dayal, Director, Department of Obstetrics & Gynaecology, CK Birla Hospital, Gurugram.

 

When hypothyroidism remains untreated, reduced hormone levels can limit oxygen and nutrient delivery to the foetus. This may lead to low birth weight, restricted growth and delayed brain development.

 

Hyperthyroidism, on the other hand, can interfere with placental function, increasing the risk of growth restriction and preterm birth.

 

Impact on brain development and learning ability

 

One of the most serious concerns linked to untreated thyroid disorders is their effect on brain development. Low thyroid hormone levels during early pregnancy can disrupt:

 

• Neuronal migration (movement of brain cells to their correct positions)
• Myelination of nerve fibres (formation of the protective coating that speeds up nerve signals)
• Formation of synapses crucial for learning and memory

 

These changes may not be immediately visible at birth but can emerge later as learning difficulties, attention problems or delayed cognitive milestones.

 

According to doctors, overt hypothyroidism poses the highest risk, though even subclinical hypothyroidism can affect intellectual development if ignored for long periods.

 

Developmental delays in infancy and early childhood

 

Children born to mothers with poorly controlled thyroid conditions may show signs of developmental delay in infancy or early childhood. These can include:

 

• Delayed motor milestones
• Speech and language difficulties
• Reduced muscle tone
• Feeding problems

 

Dr Dayal notes that behavioural issues, such as hyperactivity or poor social responsiveness, have also been observed later in life.

 

In severe cases, uncontrolled maternal hypothyroidism may contribute to intellectual disability, while unmanaged hyperthyroidism increases the risk of low birth weight and congenital thyroid problems in the baby.

 

How thyroid disorders can affect vision development

 

Thyroid hormones also play a key role in visual system development, an aspect that often goes unnoticed. Dr AAV Ramalinga Reddy, Senior Cataract Surgeon at Maxivision Super Speciality Eye Hospital, highlights that visual pathways develop alongside the brain in early pregnancy.

 

“Untreated hypothyroidism can impair neuronal migration, optic nerve myelination and retinal development, increasing risks of poor visual accuracy and delayed visual processing,” he explains.

 

Hyperthyroidism, by increasing the likelihood of premature birth, can also indirectly affect visual development.

 

Early warning signs include:

 

• Poor eye contact
• Delayed visual tracking
• Squint or abnormal eye movements

 

These often reflect deeper neurological issues rather than isolated eye problems.

 

Warning signs during pregnancy that should not be ignored

 

Thyroid-related symptoms during pregnancy are often subtle and easily mistaken for normal pregnancy changes. However, certain red flags deserve attention:

 

• Unexplained fatigue
• Sudden weight changes
• Heat or cold intolerance
• Palpitations
• Hair thinning, constipation or mood changes
• Abnormal foetal growth patterns
• Irregular foetal heart rates
• History of infertility, miscarriage or autoimmune disease

 

Routine TSH (thyroid-stimulating hormone) testing during pregnancy plays a critical role, as abnormal levels often provide the first clear indication of risk.

 

Why early screening can change outcomes

 

Timely screening and treatment can dramatically reduce risks to the baby. Detecting thyroid disorders in the first trimester allows hormone levels to be corrected before irreversible brain changes occur.

 

“Blood tests and effective therapies make thyroid disease one of the most preventable causes of developmental injury if identified and treated early in pregnancy,” says Dr Dayal.

 

Proper management significantly lowers the chances of miscarriage, preterm delivery, growth restriction and long-term neurodevelopmental impairment.

 

Can early intervention help after birth?

 

While some prenatal effects cannot be fully reversed, early postnatal intervention can make a substantial difference. Newborn screening for congenital thyroid disease enables prompt diagnosis, often within days of birth.

 

Early hormone replacement therapy supports normal brain growth, while developmental monitoring, speech therapy, physical therapy and nutritional support help address emerging delays. Regular paediatric and ophthalmic follow-ups ensure that problems are identified and managed early.

 

As Dr Reddy emphasises, early intervention does more than improve outcomes, it can fundamentally alter a child’s developmental trajectory, allowing many children exposed to thyroid imbalance in the womb to grow and thrive normally.   

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This report is for informational purposes only and is not a substitute for professional medical advice.