A baby is born with a number of 'primitive' reflexes that remind us of our very close evolutionary relationship with monkeys and apes. These disappear after varying periods of time in the baby's first year.
Sucking is a very powerful primitive reflex. On ultrasound scans it has been seen happening before birth, with the unborn baby sucking on a thumb. Some mouthing/sucking movements have been seen from about 15 weeks after conception.
From about 32 weeks of gestation, bursts of sucking and pausing, necessary for successful breastfeeding , start. A stable pattern of rhythmic sucking and swallowing starts at about 34 to 36 weeks, so that babies born early are able to feed successfully from about this stage.
The force of it is ferocious, as anyone who has put their finger on the lips of a new baby has discovered. Babies will often suck on objects in order to relieve distress, such as when they're over-tired or upset.
A very endearing early reflex of babies is the ability to snuggle. That is, when you cuddle a baby on your chest, he will burrow into your neck with great determination.
Another newborn's reflex is called "rooting", where if you tickle a baby's cheek, he will turn his head to that side and try to suck on whatever is there. This also starts around 32 weeks of gestation and is fully developed at 36 weeks. It assists the baby in finding the nipple to attach. It is gone by about one month of age.
The Moro reflex, also known as the 'startle' reflex, comes into play when a sudden backward movement of the head occurs. Your doctor or midwife might demonstrate this primitive reflex for you.
With the baby lying on his back, his head is lifted then allowed to drop a very short distance into the examiner's hand. The baby's arms and legs will fling out from his body and his back might arch. It is as if he is trying to stop himself from falling.
It is important to see that his arms and legs fling out symmetrically. If they don't, it might indicate a problem in the side that doesn't respond. A young baby will finish by pulling his arms back in, but as he matures this phase is lost.
One of the functions of swaddling a baby could be to prevent a baby being startled in this way. This reflex fades out by about three months of age.
The grasp reflex is also present at birth and, like sucking, is very powerful - so powerful that newborn babies can cling onto your fingers and hang in mid-air. It's probably best not to be tempted to test it, however, as it can fade very quickly in some babies.
Newborn babies can't open or close their hands voluntarily. However, if you put your finger into a newborn's palm, he will grasp it very firmly indeed.
In other primates such as monkeys, this reflex is necessary for clinging onto the mother while she swings through the trees. It is useless in humans so it fades away by about three months (and much earlier in some babies), to be replaced by true voluntary holding.
It is strongest just after birth. If a newborn baby is allowed to suck while grasping one of your fingers, you will notice that his grip becomes even tighter. This is thought to be another ape-like quality - the cling-and-feed reaction.
If the baby's shin touches the edge of a flat surface, his knee will flex and he'll raise his foot up and place it on the flat surface.
In the early weeks, babies also have a walking reflex. If you hold your baby up and place his feet on a surface, this will induce a crude walking movement. This doesn't come from the same part of the brain as the walking which will develop later, and it will disappear in three or four weeks.
The "gallant" reflex has been compared to a swimming movement. It happens when a baby is held face downward over your hand and the skin on either side of his backbone is scratched. The baby will flex his back to the side of the scratch.
This happens when a baby lying on his back has his head turned to one side. He looks like he is in the fencing position. The arm on the side the baby is facing is held straight out, the arm and the leg on the opposite side are flexed.
A baby will soon relax this position, even while his head is held in the same direction. If a baby gets "locked" in this position it is of concern and should be checked by a doctor. This reflex is most obvious at one month and disappears by six to seven months.
This happens when a baby is held suspended by his trunk and a forward movement is made as though he is going to fall. The child will throw his arms out to protect himself. This appears at about seven to eight months. Fortunately, it is there before walking starts! It is most obvious at around 10 to 11 months and persists throughout life.
The monitoring of these primitive reflexes coming and going, is one way an infant's progress can be checked. Their absence or persistence beyond the normal time is of concern and may indicate developmental problems.
If you are concerned that your infant does not fit the pattern described, you should see your family doctor.
Reviewed and approved by Dr Patricia McVeagh. Dr McVeagh is a Consultant Paediatrician and well-known children's health advocate. She is the co-author of Growing Healthy Children and a popular speaker on children's health issues, particularly nutrition.