Fetal Thyroid Diseases

Fetal thyroid diseases are conditions that occur when the fetal thyroid gland doesn’t develop or function properly.

The thyroid gland, a small, butterfly-shaped gland located at the base of the front of the neck, produces hormones that are critical for normal fetal and neonatal growth and brain development. Thyroid hormones control many of the body’s activities, including regulating heart rate and metabolism.

The most common fetal thyroid diseases are:

• Hyperthyroidism (overactive thyroid), where too much thyroid hormone is produced
• Hypothyroidism (underactive thyroid), where too little thyroid hormone is produced

Fetal thyroid diseases can cause serious complications for the baby and the pregnancy. Prenatal diagnosis and careful delivery and treatment planning can help prevent adverse outcomes, including neurological impairment and, in severe cases, neonatal death.

Fetal thyroid diseases may also be referred to as congenital thyroid disease, meaning they are present at birth.

Cause

Fetal thyroid diseases may be caused by:

• A genetic abnormality that affects the development and/or function of the fetal thyroid gland (in some cases the gland may be absent, incomplete or abnormally located)
• Exposure to maternal antithyroid medications or other substances that cross the placenta during pregnancy and affect fetal thyroid function
• A maternal thyroid condition during pregnancy that produces antibodies that cross the placenta and stimulate or block fetal thyroid function
• Too much or too little maternal iodine consumption

How does fetal thyroid disease affect my baby?

Fetal hyperthyroidism poses risks to the baby and the pregnancy that may include:

• Goiter (enlarged thyroid gland) that can obstruct the fetal airway, causing breathing problems at delivery and
• Accelerated bone maturation
• Intrauterine growth restriction (IUGR)
• Tachycardia (fast heart rate)
• Craniosynostosis (premature closure of the skull), associated with intellectual impairment
• Hydrops fetalis (fetal hydrops), fluid accumulation in multiple areas of the baby’s body during pregnancy
• Fetal heart failure
• Preeclampsia
• Premature labor

Fetal hypothyroidism poses risks to the baby and the pregnancy that may include:

• Neurodevelopmental delay/Intellectual disability
• Impaired growth
• Bradycardia (slow heart rate)
• Goiter (enlarged thyroid gland) that can obstruct the fetal airway, causing breathing problems at delivery
• Miscarriage

Diagnosis and Symptoms

Diagnosis During Pregnancy

In some cases, fetal thyroid disease may be diagnosed during a routine ultrasound that detects a goiter (enlarged thyroid gland) or evidence of fetal thyroid dysfunction.

A diagnosis during pregnancy enables your family and your healthcare team to plan ahead for the special treatment needs your baby may have during delivery and at birth, reducing the risk of complications. A diagnosis before birth also makes it possible for your baby to receive treatment in the womb, as needed, which may improve outcomes for your newborn.

Diagnosis After Birth

Untreated, thyroid disease in a newborn can pose serious risks, including intellectual disability (caused by hypothyroidism) and heart failure (in severe cases of hyperthyroidism). Because symptoms of thyroid disease may not be evident at birth, most states including Texas require all newborns undergo a blood test within a few days of birth to evaluate thyroid function. If the result is positive, additional testing is performed by a pediatric endocrinologist.

Symptoms of hypothyroidism vary for each baby but may include:

• Puffy face
• Thick tongue
• Lethargy
• Goiter (swelling in the neck caused by enlarged thyroid gland)
• Difficulty breathing or swallowing due to goiter
• Jaundice (yellow tint to the skin)
• Slow heart rate
• Low blood pressure, causing cold hands and feet
• Constipation
• Delayed growth and development

Symptoms of hyperthyroidism vary for each baby but may include:

• Goiter (swelling in the neck caused by enlarged thyroid gland)
• Difficulty breathing or swallowing due to goiter
• Low birth weight
• Feeding difficulties/poor weight gain
• Fast or irregular heart rate
• High blood pressure
• Bulging eyes 
• Irritability

Specialized Evaluation and Prenatal Care

If fetal thyroid disease is diagnosed during pregnancy, you may be referred to a fetal center for further evaluation and specialized care, to ensure proper treatment.

At Texas Children’s Fetal Center, we arrange for you to visit as quickly as possible for a comprehensive assessment by a team of specialists experienced in diagnosing and treating these rare fetal conditions, including maternal-fetal medicine physicians (OB/GYNs specializing in high-risk pregnancies), fetal imaging experts, adult and pediatric endocrinologists, pediatric otolaryngologists (head and neck surgeons), genetic counselors, and neonatologists.

Additional testing to confirm the diagnosis and determine the cause (hyperthyroidism or hypothyroidism) may include:

• High-resolution anatomy ultrasound to examine the thyroid gland and look for other abnormalities
• Ultra-fast MRI for a more detailed view of fetal anatomy, including the size of the airway in cases involving a goiter, for delivery planning
• Fetal echocardiogram to evaluate the baby’s heart
• Amniocentesis and chromosomal analysis to identify any chromosomal anomalies
• Fetal blood sampling, in rare cases, using a blood sample from the umbilical cord to assess thyroid function (hyperthyroidism or hypothyroidism) and guide early treatment

Following this thorough evaluation, our specialists will meet with you about the results, discuss delivery planning and treatment recommendations, and answer any questions your family has, to help you make the most informed decisions regarding your baby’s care and treatment.

Treatment During Pregnancy

Mother and baby will be closely monitored throughout pregnancy with more frequent ultrasounds to assess fetal growth and watch for signs of complications.

Treatment during pregnancy may include:

• Reduction or discontinuation of maternal antithyroid medication in cases of fetal hypothyroidism
• Administration of antithyroid medication to the mother in cases of fetal hyperthyroidism
• Fetal treatment to reduce the size of a large goiter (using injections of thyroid hormones into the amniotic sac), preventing complications at birth caused by airway obstruction and fetal neck hyperextension
• Iodine supplementation during first or second trimester in cases involving an iodine-deficient mother

Delivery

Delivery and postnatal care should be carefully planned and coordinated with a team of fetal and pediatric specialists experienced in fetal thyroid disease.

If your baby’s airway is being blocked, or obstructed, by a large goiter, your doctor may recommend a special type of delivery known as an EXIT procedure (ex-utero intrapartum treatment). An EXIT procedure is a specialized surgery performed during delivery to ensure the baby has enough oxygen at birth. We recommend delivery at a center with the expertise and resources these complicated births require, including the highest level neonatal intensive care unit (NICU).

Treatment after Birth

Treatment after birth will depend on the cause of the thyroid disease and the child’s symptoms. Treatment strategies are aimed at achieving normal levels of thyroid hormone.

Treatment strategies may include:

• Hormone replacement therapy for infants with hypothyroidism (too little thyroid hormone)
• Anti-thyroid medication or radioactive iodine for infants with hypothyroidism to reduce the amount of thyroid hormone, or surgery to remove the thyroid gland (thyroidectomy)
• Surgery in cases of a large goiter that causes breathing and/or swallowing difficulties

A unique and distinct advantage for mothers delivering at Texas Children’s Pavilion for Women is our location inside one of the largest and most renowned children’s hospitals in the world, for seamless access to the critical care services and specialists your child may need at birth.

For babies with fetal thyroid disease, this means no transfers during critical postnatal periods. It also means that the pediatric specialists responsible for treating your child have been an integral part of their care team since before birth. Our Fetal Center team works closely with specialists from Texas Children’s Thyroid Program, experts in the care and treatment of children with thyroid conditions.

Postnatal Care Team

Depending on your baby’s symptoms, his or her postnatal care team may include:

• Neonatologist
• Pediatric endocrinologist
• Pediatric surgeon
• Pediatric otolaryngologists/head and neck surgeon
• Pediatric anesthesiologist

In some cases, children with thyroid disease may require lifelong monitoring by an endocrinologist.

Why Texas Children’s Fetal Center?

• A single location for expert maternal, fetal and pediatric care. At Texas Children’s Hospital, mother and baby receive the specialized care required for the diagnosis and treatment of fetal thyroid disease all in one location, for highly coordinated care and treatment planning.
• A skilled, experienced team with proven outcomes. We have a dedicated team of maternal-fetal medicine specialists, fetal imaging experts, adult and pediatric endocrinologists, pediatric head and neck surgeons, pediatric anesthesiologists, neonatologists and others who work in concert to care for you and your baby every step of the way, using proven protocols we’ve developed over the years. With their combined expertise and unified approach, this team offers the best possible care for pregnancies involving fetal thyroid disease.
• We care for your child’s needs at every stage of life. Our comprehensive approach starts with your first prenatal visit and continues through delivery, postnatal care, and throughout childhood, thanks to one of the nation’s leading teams of fetal and pediatrics specialists for the care and treatment of rare congenital conditions.

Videos

• Texas Children’s Fetal Center: Our care began before he/she was born

Additional Resources

• 6 things to consider when choosing a fetal center