- low birth weight.
- placing the child on his back to sleep.
- young maternal age.
- maternal smoking during pregnancy.
Number 2 is correct.
Placing the baby on his back to sleep is recommended by the American Academy of Pediatrics, because stomach or side sleeping carries a higher risk of SIDS. Other risk factors include low birth weight, young maternal age, maternal smoking during pregnancy, co-sleeping with parents or siblings, anemia, and male gender.