New Sibling Adjustment and Regression
The short answer
Behavioral regression after the arrival of a new sibling is one of the most common and predictable responses in toddlers. Children may temporarily lose skills they had mastered — such as toilet training, sleeping independently, or self-feeding — as a way of coping with the enormous change in their family. With patience and reassurance, most regressions resolve within a few weeks to a couple of months.
By Age
What to expect by age
Not applicable — this concern applies to the older sibling adjusting to a new baby. However, if your older child is under 18 months, they may not show obvious regression but could become more clingy, fussy, or have disrupted sleep patterns as they sense changes in routine and parental attention.
Not applicable for the newborn. For toddler siblings (18-24 months) adjusting at this stage, regression in sleep habits and increased clinginess are the most common signs. They may want to be held more, refuse to walk, or demand a bottle or pacifier they had given up.
Not applicable for the newborn. For older siblings aged 2-3, regression often peaks around the time the new baby becomes more interactive (smiling, grabbing toys). Toddlers may have potty accidents, revert to baby talk, or become more defiant as they process the permanent nature of sharing their parents.
For the older sibling, regression may ebb and flow over the first year. Major milestones in the younger child — crawling, walking, getting into the older child's toys — can trigger new waves of regression. Consistent routines, one-on-one time with each parent, and acknowledging the older child's feelings all help. Most children fully adjust within 3-6 months.
What Should You Do?
When to take action
- Your toddler has potty accidents, wants a bottle or pacifier again, or uses baby talk after the new baby arrives
- Your child is more clingy, whiny, or has trouble sleeping for the first few weeks or months after the baby is born
- Your toddler alternates between loving the baby and expressing frustration or disinterest
- Regression comes and goes in waves, particularly during stressful moments or when the baby is getting more attention
- Regression persists beyond 3-4 months without any improvement, or your child seems increasingly withdrawn or sad
- Your older child is consistently aggressive toward the baby despite redirection and supervision
- Your child shows signs of anxiety such as excessive worry, new fears, or significant changes in appetite or sleep that do not improve
- Your child is deliberately trying to harm the baby and shows no response to redirection or concern for the baby's safety
- Your child shows severe emotional disturbance such as prolonged inconsolable crying, self-harm, or complete refusal to eat or drink
Sources
Related Resources
Related Behavior Concerns
Sibling Rivalry in Toddlers
Sibling rivalry is a completely normal part of child development and is nearly universal in families with more than one child. Toddlers are naturally egocentric and have limited ability to share, take turns, or manage frustration — all of which fuel sibling conflict. While it can be exhausting for parents, most sibling rivalry decreases as children develop better language and emotional regulation skills.
Toddler Jealousy of New Baby
Jealousy toward a new baby is one of the most natural and expected toddler emotions. Your older child has had your undivided attention and is now learning to share it — a monumental adjustment. Jealousy may show up as clinginess, acting out, regression, or even asking to send the baby back. With empathy, dedicated one-on-one time, and patience, most toddlers gradually adapt within a few months.
Toddler Hitting Baby Sibling
It is very common for toddlers to hit, push, or be rough with a baby sibling. Toddlers have limited impulse control and cannot fully understand that the baby is fragile. This behavior is usually driven by jealousy, frustration, curiosity, or a desire for attention rather than malice. Close supervision, calm redirection, and teaching gentle touch are the most effective strategies.
Aggressive Play vs Normal Play
Rough-and-tumble play — wrestling, chasing, play-fighting, and superhero battles — is a normal and important part of child development, particularly for toddlers and preschoolers. It helps children develop physical coordination, social skills, self-regulation, and an understanding of boundaries. The key distinction between normal rough play and concerning aggression is whether both children are having fun, there is turn-taking in roles, and no one is intentionally trying to hurt the other.
My Toddler Is Aggressive Toward Pets
Toddlers being rough with pets is extremely common and almost never reflects true aggression or cruelty. Young children lack the motor control to be consistently gentle and do not yet understand that animals feel pain the way they do. With patient, consistent teaching about gentle touch and close supervision, most toddlers learn to interact safely with pets by age 3-4.
My Baby Doesn't Seem Attached to Anyone
By 7-9 months, most babies show clear preferences for their primary caregivers and some wariness of unfamiliar people. If your baby seems equally comfortable with everyone and shows no distress when separated from caregivers, it may simply reflect an easy-going temperament. However, if combined with other social differences, it can occasionally warrant further discussion with your pediatrician.