“Back is Best”... and Here’s Why

The safest sleep position for your newborn is on their back, every sleep, every time.

The American Academy of Pediatrics (AAP) recommends this because back sleeping:

  • Keeps the airway clear and open

  • Reduces the risk of overheating

  • Protects against rebreathing carbon dioxide, a known Sudden Infant Death Syndrome (SIDS) risk

Since the launch of the Back to Sleep® campaign in the 1990s, SIDS rates have dropped by more than 50%. That’s the impact of one simple, science-backed step.

Why Babies Love Belly Sleeping

Many parents notice that babies often seem calmer and sleep more soundly on their stomachs. This makes sense because:

  • The womb was snug, and pressure against the belly feels familiar

  • The startle reflex is strong, and tummy pressure reduces sudden jerks that wake them

  • Digestive comfort is sometimes better when lying face down

But here’s the developmental truth: in the early months, your baby’s neck strength, airway reflexes, and motor control are not developed enough to make belly sleeping safe. They cannot reliably lift or turn their heads if their breathing becomes blocked.

Developmental Sleep Timeline: From Newborn to 1 Year

0–3 Months: Newborn Stage

  • Back to sleep only, every sleep

  • Swaddling or a sleep sack helps reduce startle reflex

  • No belly or side sleeping; neck muscles are too weak

  • Focus on tummy time: short 3–5 minute sessions, several times a day

  • Games to try: chest-to-chest snuggles, mirror play, gentle face-to-face interaction

4–6 Months: Rolling Stage

  • Always start sleep on the back

  • Babies may begin rolling back to belly and belly to back

  • Stop swaddling; arms must be free for safe rolling

  • Tummy time builds arm, shoulder, and core strength

  • Games to try: toy reach, tummy time with a pillow, play at eye level

6–9 Months: Rolling & Mobility Stage

  • Start every sleep on the back; if baby rolls both ways, they may choose their position

  • Use a firm mattress with a snug fitted sheet, no loose bedding

  • Encourage rolling, pivoting, and supported sitting

  • Games to try: rolling games with toys, supported sitting with pillows, peekaboo crawls

9–12 Months: Independent Sleeper Stage

  • Begin sleep on the back, but if baby rolls to their tummy, it is safe to let them stay

  • Keep the sleep environment clear of blankets, pillows, or toys

  • Encourage crawling, pulling to stand, and early cruising

  • Games to try: tunnel play, ball chasing, and assisted cruising along furniture


Quick Takeaway

Your baby’s milestones guide their safest sleep position:

  • 0–3 months: Back only, with tummy time for play

  • 4–6 months: Back to sleep, rolling begins, longer tummy play

  • 6–9 months: Movement expands — rolling, sitting, crawling

  • 9–12 months: Independent sleeper choosing their own position


The Milestone That Changes Everything

By 4–6 months, when rolling skills develop, your baby gains the ability to reposition themselves. By the time they can roll confidently both ways, their neck muscles, reflexes, and mobility keep them safe even on their belly.

Think of it this way:

  • Newborns need you to place them on their backs

  • Rolling babies need space to move safely

  • Older infants can self-select their own sleep position


Bottom Line for Parents

It can be tough when your baby prefers belly sleep, but the research is clear:

  • Place your baby on their back for the first year

  • Provide supervised tummy time to build strength

  • Allow belly sleeping only once your baby rolls both ways independently

Your baby’s sleep journey changes rapidly in the first year. In the beginning, you are responsible for positioning them safely. With time and developmental milestones, your baby becomes capable of choosing their own sleep position.

By combining safe positioning with a clear sleep environment, you are protecting your baby and supporting healthy development.


Trusted Resources for Parents


More Resources from Harbor on All Things Sleep