your baby sleeps in your womb prepares her for sleep after birth, and paying
attention to that can help you prepare for supporting her nighttime needs.
Modern ultrasound techniques give
researchers the opportunity to glimpse babies’ movements long before they
are born. By the time you are eight to twelve weeks pregnant, your unborn baby
can move in a variety of ways and has bursts of activity alternated with
periods of rest.
During the periods of rest, your baby moves very little and
is less sensitive to sounds and light from outside your womb. Some
researchers think that the periods of activity can be related to periods of
wakefulness and the periods of rest to periods of sleep after birth.
However, sleep and wake states are defined according to neurological
criteria and can only be truly identified when your baby’s brain is
As your pregnancy progresses, the cycles of activity and
rest become longer and more regular. By the time you are about 20 to 28
weeks pregnant, a whole cycle of rest and activity lasts for between 40 and
60 minutes. Around this time, your baby’s arm, leg and eye movements become
more synchronized with each other and with changes in their heart rate. This
is considered to be a major milestone in their neurological development.
When you are 30 weeks pregnant, your baby “rests” for over half of the time.
As your due date approaches, the amount of time that the baby rests
In unborn babies, three sleep states have been described and
can be identified on the basis of specific patterns of brain activity and
changes in heart rate and eye movements. These states are known as “active,”
“quiet” and “indeterminate” sleep. Active sleep can be seen as the precursor
of REM sleep in older babies, children and adults. Quiet sleep can be seen
as the precursor of non-REM sleep, although the stages in non-REM
sleep only emerge weeks or even months after birth. Indeterminate
sleep is when the criteria for none of the other states, including
wakefulness, are met and is a result of a baby’s brain not yet being mature
enough to organize all of its activities all of the time.
From when you are about 28 weeks pregnant, the periods that
your baby spends awake and in active and quiet sleep states can be
identified, although he or she still spends a lot of time in the
indeterminate sleep state. Between 32 and 34 weeks, the amount of
organization between a baby’s patterns of brain activity, changes in heart
rate and eye movements increases remarkably. This means that, as you
approach the end of your pregnancy, your baby spends gradually less time in
the indeterminate sleep state and more in the quiet sleep state. Your baby
also starts to display some of the characteristics of mature sleep-wake
behavior. For instance, urination only occurs when the baby is awake and, if
it is a boy, most of his penile erections occur when he is in the active
During the last three months of your pregnancy, your baby’s circadian
rhythms start to emerge. Circadian rhythms are variations in body processes,
such as heart and breathing rates, temperature, blood pressure and the
secretion of some hormones, which take place on a cycle lasting
approximately 24 hours. These are controlled by a biological clock in your
brain and help you to feel sleepy at night and awake during the day. Your
baby’s heart rate is clearly synchronized with the periods that you are
awake and asleep and the rhythms in your heart rate, body temperature and
hormone production. At the end of your pregnancy, your baby has developed
his or her own circadian rhythm controlled by his or her own biological
clock. However, these are still supported by hormones from your body that
pass through the placenta to your baby. After your baby is born, you can
continue to support his or her circadian rhythms and biological clock by
breastfeeding on cue, as these hormones also pass into your breast milk and
are absorbed by your baby.
In your womb, your baby is not completely isolated from your
environment. However, neither vibrations on or around your body or high
levels of white noise seem to affect how he or she sleeps. Perhaps
surprisingly, babies even appear to sleep during labor. Your unborn baby’s
sleep can be influenced by recreational or prescription drugs that you use
and by your state of mind. If you consume a lot of caffeine, your baby will
probably spend more time “awake” than otherwise and if an opiate antidote
were to be given to you, your baby would spend more time in active sleep and
awake states than normal, particularly in the first hour after you had taken
If you take some types of antidepressants, your baby will
spend more time in the active sleep state and be more easily startled after
birth. Some pain relief medications that you may receive during labor can
reduce the amount of time that your baby spends in quiet sleep. And the use
of recreational drugs such as tobacco, alcohol, marijuana and more serious
drugs like cocaine will not only harm your and your baby’s health but affect
their sleep; smoking during pregnancy puts your child at an increased risk
of sudden infant death syndrome.
If you are particularly anxious, it is likely that your baby
will spend more time in the quiet sleep state and move less while sleeping,
than if you are less worried.
Events during your pregnancy and labor can affect how your baby sleeps after
birth and even into the preschool years. For instance, if your baby is your
first or is born by Caesarean section, he or she may have more active sleep
and less quiet sleep. Your mood and diet may also influence your child’s
sleep after birth. If you are very anxious during your pregnancy, your baby
may sleep for longer, but more restlessly, right after birth and have more
sleep problems after the first few months. However, if you have higher
levels of the fatty acid DHA in your blood, your baby may have more quiet
sleep, spend more time awake and have fewer transitions between sleep
states. Even if your pregnancy lasts more than 37 weeks, the amount of quiet
and motionless sleep that your baby has after birth will increase as the
length of your pregnancy increases. This indicates that
his or her brain has reached a higher level of maturity.
The level of maturity that your baby’s brain reaches before
birth is an important factor in how he or she will sleep after birth. You
can support the maturation of your baby’s brain by eating a balanced and
varied diet rich in omega-3 fatty acids and avoiding recreational drugs.
By preparing for labor well and obtaining information on
natural methods of pain relief, you can minimize the probability that you
will need medications during labor and even lessen your chances of requiring
a Cesarean section. If you have good information and guidance about
breastfeeding, you will have more chance in succeeding with nursing and
hence in being able to support your baby’s circadian rhythms and biological
clock with your hormones.
Preparing for Baby
Whatever you do to support your baby’s sleep patterns, it is
unrealistic to expect your baby to sleep through the night in the first
months or even years of life. It is normal for you and your baby to need
night-time breastfeeds for months rather than weeks. You may need to
breastfeed at night to reduce the possibility of your breasts becoming too
full, milk ducts getting blocked, or even mastitis developing.
Your baby may need to breastfeed at night to ensure optimal
growth, to prevent dehydration or low blood sugar levels, to maintain
defenses against illnesses, to regulate bodily processes or to help him or
her sleep. For this reason, it can be very helpful to prepare somewhere that
you and your baby can rest and sleep together safely. Consider and remain
open to a number of options, such as a bed for you and your baby to share, a
separate cot or crib in your bedroom, a co-sleeper and a sleeping mat for
you on the floor of your baby’s own room.
Above all, remember that your baby sleeps and wakes in a
certain way because that is how babies are. Your baby does not wake up at
night or demand closely spaced breastfeeds to annoy you, but because that is
what he or she needs. As your baby grows and the brain matures, he or she
will gradually start to sleep for longer periods.
Rebecca Holman is the mother of two
small boys, Thomas and Daniel. She was born and grew up in the U.K.
and has a degree in mathematics and statistics. She became interested in infant sleep after hearing a
lactation consultant say that sleeping through the night was a
matter of neurological development, not training. She has come to
believe that the way breastfed children and their mothers sleep
should be considered normal, and that mothers should not be
pressured into “sleep training.” Read
another article on sleep by this author.