The effect of substance use during pregnancy on physical development
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Children who were exposed to substances before birth may grow and develop differently from their peers.
Common physical differences can include:
Smaller birth size or slower weight gain
Differences in muscle tone (stiffness or low tone)
Delays in early motor milestones (rolling, crawling, walking)
Sensitivities to light, sound, textures, or touch
Irregular sleep patterns or difficulty self-soothing
You might also notice differences in sleep patterns or sensitivity to light, sound, or touch. These reactions are the child’s way of managing a nervous system that works a bit harder to stay balanced.
Neonatal Abstinence Syndrome (NAS)
Certain substances also put the fetus at increased risk for Neonatal Abstinence Syndrome (NAS). If a mother’s nervous system is affected by a substance she used during pregnancy, there’s a good chance the baby’s nervous system will be affected too. During pregnancy, the baby’s body is used to getting the drug, and after birth – when the substance is no longer available – the baby can experience withdrawal symptoms:
Irritability
High-pitched crying
Jitteriness
Sweating
Vomiting
Diarrhea
Seizures
Respiratory distress
The type of drug, length of exposure, and whether a baby is born full-term all affect the severity of Neonatal Abstinence Syndrome.
Prenatal exposure to alcohol can also lead to fetal alcohol spectrum disorders (FASDs), which carry other physical developmental issues.
What helps:
Children exposed to substances before birth may grow and develop at their own pace. They reflect how their bodies and nervous systems got an early, challenging start.
Early intervention makes a difference and can set the child on a path to a healthier future. Parents and caregivers play an important role by providing consistency, steady routines, plenty of calm sensory experiences, and playful opportunities for movement. Physical and occupational therapy can also support muscle tone, coordination, and sensory regulation.
For foster and adoptive parents, remembering that physical differences often reflect early biology – not anything that happened in your care – is important. Your safe, consistent environment is a protective factor that supports steady progress.