Exactly when and how your baby develops a cycle of sleeping and waking before birth remains a bit of a mystery. It's not known whether your own rhythms influence your baby's sleep-wake cycle or whether your baby develops his own internal clock. Indeed, such a clock might be triggered in response to the small amount of light that is able to penetrate through the uterus during the last few weeks of pregnancy. It's apparent from brain scans, however, that by this stage of pregnancy, your baby does have very separate periods of activity.

There is a clear cycle, alternating between periods of quiet rest, sleep with rapid eye movements (REM), wakefulness with activity but no eye movement, and wakefulness with lots of activity and eye movements. During this sleep-wake cycle, the baby's actions becomes more coordinated as periods of activity are linked to rhythmical breathing and increased heart rate, and eye movements.

By this stage of pregnancy, electrical activity in your baby's brain shows patterns reflecting periods of sleep or wakefulness. An EEG of your baby's brain would show that the quietest period, deep sleep, takes up almost half of the time. The next most common state is REM sleep (the sleep stage during which children and adults dream). This is a time of great electrical activity within your baby's brain. During REM sleep the baby may be quiet or making lots of movements, so it's not possible to tell whether your baby is truly awake at this time or if he's dreaming. Paradoxically, the least electrical activity happens when your baby is most awake-in fact less than 10 percent of your baby's time is spent truly awake at this stage.

The blood in your baby's umbilical cord contains "cord blood," which is rich in stem cells. These cells are the building blocks of organ tissue, blood, and the immune system. Some parents save these cells and store them (in a private facility at a cost) in the event that their child or another family member needs their healing benefits (see Stem cell collection).

Studies have found that they are very effective in the treatment of more than 70 diseases including juvenile diabetes, cancers, heart disease, and brain injury.

Stem cells are widely used, but there is significant evidence to show that using cells from the cord blood of a sibling or other family member is more effective than using cells from an unrelated donor, or bone marrow from relatives.

Cord blood can be expensive to store. Some women choose to donate their blood to public cord blood banks. The donated blood is stored, and this is used to treat patients who need it most. Talk to your doctor if you'd like to do this.