Rett Syndrome in Babies: Early Signs and Prenatal Testing

Your baby has been meeting milestones — rolling over, reaching for toys, and responding to your voice. Then, around their first birthday, you notice something different. The babbling becomes quieter. Their hands move in repetitive patterns. These changes can feel confusing, but understanding what’s happening can help you know what to watch for.

Rett syndrome is a rare genetic disorder that affects brain development. According to the journal Systematic Reviews, Rett syndrome occurs almost exclusively in females. The condition follows a distinct pattern. Babies usually grow and develop normally during their first months of life, then show changes in how they develop.

This article explains the symptoms parents might notice, why changes often become clearer after six months, what prenatal testing can and can’t do, and how early support may help.

Understanding What Happens in the Brain in Rett Syndrome

Most cases of Rett syndrome are caused by a mutation (change) in the methyl-CpG binding protein 2 (MECP2) gene, which helps control brain development. A mutation is a change that prevents a gene from working correctly. This mutation occurs spontaneously on the X chromosome. Typically, females have two X chromosomes and males have just one, which explains why Rett syndrome happens almost only in females.

The MECP2 gene produces a protein that helps regulate how other genes support brain development and function. When this gene doesn’t work right, the protein can’t do its job, which can lead to developmental changes around the time babies reach complex milestones.

Recognizing the Timeline of Development

Babies with Rett syndrome usually follow a pattern of growth that makes the condition easier to identify over time.

Expecting Typical Growth in the Initial Months

Most babies with Rett syndrome grow as expected during their first months of life, typically until around 6 to 18 months of age. They reach early milestones, such as watching people and objects, showing lively facial expressions, and using their hands with purpose. Parents and pediatricians usually don’t notice concerning behaviors during this period.

Understanding the Window of 6 to 18 Months

Rett syndrome changes typically begin between 6 and 18 months of age. During this time, babies are developing skills such as sitting independently, using hands purposefully, and learning early language. These developmental steps rely on the MECP2 protein working properly. When MECP2 doesn’t function as it should, brain development begins to slow or change. The timing and severity vary from child to child.

Some early signs may be easy to miss. Babies may show slowed growth or fall behind on milestones they were close to reaching. Hypotonia (low muscle tone) can make babies feel very floppy when picked up. Some babies may seem unusually calm and quiet, remaining still and rarely fussing.

Noticing the Signs of Regression

The main sign of Rett syndrome is regression — losing skills that had been gained. Babies who once held bottles, picked up toys, or pointed slowly lose these purposeful hand abilities. Parents might notice their baby dropping items often or becoming unable to use their hands like they did before.

Communication regression often occurs with hand skill changes. Babbling may get quieter or stop. Some babies who had begun saying words may stop using them. Developmental delays may also show up in motor skills like sitting independently, crawling, or pulling up to stand.

Identifying the Distinct Warning Signs

Three key features often help doctors and parents recognize Rett syndrome.

Repetitive Hand Movements

One of the easiest features to spot in Rett syndrome is stereotypies — repetitive, patterned hand movements that happen unintentionally. These movements replace purposeful hand use. Common patterns include hand-wringing, repetitive clapping or tapping, and frequent hand-to-mouth movements.

Changes in Eye Contact and Social Connection

Many babies with Rett syndrome show reduced eye contact and social engagement. They may seem less interested in people or their surroundings and respond less when their name is said. This can at first look like autism spectrum disorder, a developmental condition that can affect communication and social interaction.

However, many children with Rett syndrome later develop an intense, meaningful eye gaze during childhood. Their eyes often become a main way they connect with others, which differs from typical autism patterns.

Slowed Head Growth

Between 6 and 18 months of age, many babies with Rett develop acquired microcephaly — head growth slows down compared to body growth after a period of typical development. The head doesn’t get smaller but grows more slowly than expected, so head size drops on growth charts. This slowed head growth reflects changes in brain development and is often an important clue when diagnosing Rett syndrome.

Learning About Prenatal Testing Options

Understanding what prenatal testing can and can’t do helps set realistic expectations.

Why Routine Prenatal Screens Don’t Detect Rett Syndrome

Many parents ask why Rett syndrome wasn’t detected during pregnancy. The answer lies in the difference between chromosomal conditions and gene mutations. Routine prenatal tests, such as noninvasive prenatal testing, generally screen for chromosome problems — missing or extra chromosomes, such as those seen in Down syndrome — not specific gene mutations.

Rett syndrome is caused by a specific mutation in the MECP2 gene. The X chromosome itself is present and appears typical on these screening tests. Because babies with Rett syndrome also develop typical physical features before birth, ultrasounds don’t show warning signs. For these reasons, the condition usually goes undetected until after birth.

In more than 99 percent of cases, the MECP2 mutation occurs spontaneously when the baby begins to develop. This is called a de novo (Latin for “new”) change. The mutation shows up for the first time in the child and wasn’t passed down from either parent. It’s not something either parent carries or could have predicted.

When Prenatal Testing May Be Considered

Specific genetic testing is available but not routine. Testing may be considered if a family has a child with Rett syndrome and a known MECP2 mutation. In rare cases — about 0.5 percent — the mutation can be inherited from a mother who carries the change but has few or no symptoms. Genetic counselors can help family members understand gene changes and what they mean for future pregnancies.

Prenatal genetic testing can identify whether an MECP2 mutation is present, but it can’t predict if the mutation will cause Rett syndrome or how severe the symptoms may be. MECP2 changes can affect people differently.

Supporting Your Baby’s Development

Although there’s currently no treatment that can correct the root genetic cause of Rett syndrome, supportive therapies can help manage symptoms and improve quality of life.

Starting Early Intervention Therapies

Physical therapy helps promote balance and walking while working to prevent joint stiffness. Occupational therapy supports hand use for daily activities such as feeding and dressing. When repetitive hand movements are a major concern, therapists sometimes use splints that gently limit elbow or wrist motion.

Speech therapy brings in supportive communication methods early. Eye gaze technology — special devices that track where a child looks — can be especially helpful. Many children show strong eye contact and can use their eyes to select words or pictures on communication boards.

Building Your Care Team

Managing Rett syndrome involves a team of healthcare professionals. Neurologists and developmental pediatricians diagnose the condition and help manage medical concerns. Physical, occupational, and speech therapists support motor skills and communication. Dietitians can help when feeding difficulties affect nutrition.

Medications may help manage symptoms such as seizures, muscle stiffness, breathing problems, or sleep issues.

Taking the Next Steps

Understanding Rett syndrome’s typical pattern helps families spot signs of regression early and get support. Prenatal testing isn’t routine but may be considered when there’s a known family history. Early intervention can help children with Rett syndrome develop their abilities.

Consider keeping a record of your baby’s milestones and any changes you notice. Share concerns about hand movements, eye contact, or missed steps with your child’s pediatrician. It may also be helpful to connect with Rett syndrome family organizations or online support groups while waiting for appointments.

If you notice changes in your baby’s development, talk with a healthcare provider. Early evaluation can help your family get support and connect with specialists who understand Rett syndrome.

Join the Conversation

On MyRettTeam, people share their experiences with Rett syndrome, get advice, and find support from others who understand.

What was the first change that made you pause and wonder if something was different in your child? Let others know in the comments below.