What are the Early Signs of Rett Syndrome Stage 1?

Rett syndrome is classically described as having a period of normal development followed by regression, but looking back, many parents realize there were incredibly subtle clues early on. During Stage 1 (often called Early-Onset Stagnation), which typically spans from 6 to 18 months, infants may exhibit decreased eye contact, generalized “floppiness” (hypotonia), delays in motor milestones like crawling, and a noticeable deceleration in head growth ^[1]. Because these signs are mild, non-specific, and sometimes masquerade as an infant just being “very good” or placid, they are almost universally missed by both parents and pediatricians at the time ^[2].

Why Stage 1 Signs Are So Easy to Miss

When you are in the thick of a baby’s first few months, subtle deviations in development are difficult to spot. It is incredibly common for families to only recognize these signs in hindsight or when reviewing old home videos ^[3]. During the earliest phases of Rett syndrome, the clinical changes are subtle and overlap heavily with general developmental delays or other genetic conditions ^[4][2]. It is important to know that missing these signs is not a failure on your part—or even your pediatrician’s part. The diagnostic criteria have evolved precisely because early identification is profoundly challenging before more obvious symptoms appear ^[2].

Subtle Early Clues in the First Year

The “Placid” Baby and Social Disconnect

Many parents retroactively describe their infant as having been an exceptionally “good” or placid baby. While easy temperament is often celebrated, in hindsight, this placid behavior is sometimes linked to a decreased interest in their surroundings and early differences in social reciprocity ^[5][3].

• Decreased Eye Contact: You might have noticed that your baby didn’t consistently hold your gaze, or their selective attention seemed compromised ^[6].
• Social Reciprocity Changes: Some infants initially interact as expected but begin showing a drop in social responsiveness—such as failing to respond to their name or offering fewer smiles—between 5 and 12 months ^[5][7].
• Fewer Gestures: A restricted use of intentional gestures, like pointing or waving, is a subtle early social “red flag” ^[7].

Hypotonia and Motor Delays

Before any loss of skills occurs, the acquisition of new skills often slows down.

• Floppiness (Hypotonia): Infants may feel unusually “floppy” or lack typical muscle tone ^[8][9].
• Delayed Crawling or Sitting: Because of this lowered muscle tone, motor milestones such as rolling, sitting, or crawling might be delayed or achieved atypically ^[4].

A Plateau in Head Growth

One of the hallmark physical signs of Rett syndrome is a deceleration in head growth ^[10]. While a baby’s head size might start out in a typical percentile, you or your pediatrician might eventually notice that the growth curve flattens or drops across percentiles. This plateau in head circumference (acquired microcephaly, meaning a smaller-than-typical head size that develops over time) can begin early—sometimes noticeably shifting on growth charts around 2 to 3 months of age, but usually becoming much clearer within the 6 to 18 month window ^[10]. It often isn’t flagged by doctors until a consistent pattern of dropping percentiles emerges over several checkups ^[2].

Unusual Vocalizations

Research analyzing home videos has pinpointed subtle differences in early vocalizations. Infants with typical Rett syndrome often fail to reach complex speech milestones like canonical babbling (repeated consonant-vowel sounds like “ba-ba-ba”) or early proto-words ^[7]. Additionally, some infants make unusual sounds, such as high-pitched, crying-like noises mixed with normal cooing, or vocalizing on an inspiratory airstream (making sounds while breathing in) ^[7].

Explaining This Stage to Others

When well-meaning friends or extended family ask, “But wasn’t she developing perfectly normal as a baby?”, it can be exhausting. A helpful way to explain it is: “She was an incredibly easy baby, but her doctors have explained that being unusually ‘placid’ and having very subtle motor delays were actually the earliest, quiet signs of Rett syndrome before the major symptoms started.”

Validating Your Experience

Looking back and realizing there were signs can bring up complex emotions, including guilt or frustration that doctors didn’t catch it sooner. Validating these early Stage 1 signs is essential—it confirms what you likely sensed but couldn’t quite put your finger on. These subtle hints are an established part of the Rett syndrome trajectory, not signs you were expected to decode on your own. Acknowledging this can help you better understand the bridge between those quiet early months and the more obvious losses of skills (regression) that characterize Stage 2.