Sleep Cycles

• During "quiet" sleep, babies are less likely to be woken by loud noises.Sky View/Photodisc/Getty Images
  
  When babies are born, they haven't yet developed mature circadian rhythms. This means that they do not yet understand the difference between night and day. It can often take many months before a baby starts to settle in for longer periods at night. Baby sleep cycles are also much shorter and differ in nature from adult sleep cycles. An adult sleep cycle lasts from 90 to 100 minutes. The adult passes through several stages of sleep, including deep sleep and REM (Rapid Eye Movement) sleep. When you have completed the cycle, you will either wake up or return to an earlier stage of sleep. Baby sleep cycles are only 50 to 60 minutes for the first nine months. A baby's sleep cycle is simpler, as it only has two stages: "active" and "quiet." Active sleep occurs when the baby first falls asleep and is like adult REM sleep. Halfway through the sleep cycle, babies will pass into quiet sleep, where the breathing is more rhythmic and the baby is quiet.
  
  

Sleep Patterns

• Baby sleep patterns are determined by hunger and shorter sleep cycles.Rayes/Lifesize/Getty Images
  
  Baby sleep patterns -- meaning when and how much the baby sleeps during a 24-hour period -- vary enormously. Newborns sleep between 16 and 18 hours per day. Babies generally wake up hungry every two to four hours. They need to be fed often to ensure that they grow properly. Breastfed babies are likely to sleep for shorter amounts of time, as breast milk is lighter than formula and therefore does not stay in the stomach as long. By 3 weeks old, the baby may sleep for longer periods, three to four hours at a time, and stay awake for longer periods. By the time the baby is 4 months old, she may sleep through the night and will do most of her sleeping at the night, with two naps during the day. The average amount of sleep for a 4-month-old is 12 hours during a 24-hour period.
  
  

Sleep & SIDS

• Babies that are aroused more easily from sleep are at less risk for SIDS.Jupiterimages/Creatas/Getty Images
  
  Active sleep is when baby is safest in his sleep cycle and at the lowest risk from SIDS (Sudden Infant Death Syndrome). SIDS generally occurs during sleep, so it it vitally important when settling a baby down for the night that it is done correctly. Babies who are at most risk from SIDS are those who live with a smoker, are placed on the stomach to sleep, are sleep-deprived, are recovering from an infection or sleep in a room that is too warm. To prevent SIDS, always place the baby on his back to sleep, ensure that bedclothes cannot be pulled over the head and baby cannot get tangled within them, and room temperature should be kept below 75 degrees Fahrenheit to ensure that baby does not overheat.
  
  

Age and Changes in Sleep Patterns

• Sleep patterns will gradually change as the baby gets older.Jupiterimages/Pixland/Getty Images
  
  As babies get older, their sleep patterns change according to their needs. Babies continue waking during the night until they have grown to a point where they can go for longer periods without feeding. By the age of 6 months, a baby should sleep through the night for an average of 11 hours. The baby will still take about two short naps during the day. By this age, the child should now differentiate between day and night and have a little more understanding of the world around her. At this stage, non-REM sleep should have begun, but it is not until a child is school-aged that her sleep cycles will resemble those of an adult.