The averageweighs 3.4kg, with boys tending to weigh a little more than girls. The baby’s length averages about 50cm, although this is often difficult to measure accurately as new babies tend to curl up when you try to measure them. Another measurement that is usually checked is the circumference of the head. This is useful in assessing the baby’s progress in the first year of life. Measurement is from the forehead to the rearmost prominence (the occiput), and averages about 35cm in a . Extreme variations to this average may indicate brain malformation or a condition such as hydrocephalus (abnormally large amount of fluid in the brain). At the end of the first year the head circumference is about 47cm (it is about 41cm after three months, 44cm after six months).
The new baby has a relatively large head, and usually rather chubby arms and legs and a prominent tummy. He or she may be covered in vernix caseosa, a sticky white substance that protected the baby from becoming waterlogged in the uterus. It is not necessary to wash off the vernix immediately after birth, indeed, some doctors believe that the baby would thus be deprived of some important substances.
The amount of hair on the baby’s head varies from practically none to a thick growth. Babies who are born a little later than their due date tend to have more. There may still be fine, fuzzy hair elsewhere on the body, called lanugo hair, which covered the baby while in the womb. This will rub off and disappear during the first week or two.
On the top and towards the front of the baby’s head is a soft spot between the unfused skull bones, one of the fontanelles. This varies in size and shape, and gradually closes over during the next 18 months. In a normal baby it is a shallow dent through which you can feel the pulsations of the baby’s blood circulation. Sometimes the baby’s head seems to be an alarming shape at first, especially if there has been a long second stage of labour. This is because the pressure on the head as it comes through the birth canal causes the soft bones of the skull, which are not yet fused together, to move over each other slightly. This moulding helps to make the baby’s head a little easier to push through the canal. The pressure may also cause swelling of the presenting (foremost) part of the baby, most usually the top of the head, in a condition called caput succedaneum.
Another cause of swelling of the head resulting from delivery is a cephalhaematoma, or bleeding into the scalp. Although it sounds alarming it usually is not dangerous. It is not very common and is not obvious at first, becoming more noticeable on the second day. It does take some time – maybe several months – to subside but tends to disappear completely.
As with the baby’s head, the eyes may also be puffy and swollen at first if the labour was long. Stickiness of the eyes is quite common, and is usually remedied by bathing. Some babies may look as though they are squinting, even though they have perfectly normal eyes, and parents should not jump to wrong conclusions too soon. On close examination, the baby will be found to have folds of skin at the inner corners of the eyes that give them this appearance of squinting. Parents who are in any doubt should ask the doctor or midwife’s advice. Swollen breasts are normal in newborn babies of both sexes because maternalcross into the baby’s circulation via the placenta. Sometimes these hormones even cause a milky discharge from the nipples, which settles down within a few days.
The baby’s skin is usually pink; babies of blacks or other dark-skinned people are usually paler when they are born, the skin darkening as they grow older. Sometimes babies who are usually going to have quite dark skin have bluish patches on the body, often on the back. These are called Mongolian blue, and are not bruises but just pigmented areas that gradually fade. New babies often have sites of red discoloration on their eyelids, neck or on their forehead. These spots are in fact widened blood vessels. This condition is known as stork bite, or naevus flammeus, and disappears spontaneously after a few months. Sometimes in the first week tiny white dots can be seen on the face. These are caused by a temporary blockage of the sebaceous glands and need no treatment. The baby’s skin may be quite dry, and peel in places, especially if the delivery was after the expected date, but soon returns to normal.
It is quite normal for ato appear slightly yellow – jaundiced – during the first days, or week or two of life.
Over half of normal full-term babies have mild. It is caused by the baby’s liver having only a limited ability to excrete all the yellow bile pigment, bilirubin. The condition tends to be a little more prolonged in breastfed babies, but is quite harmless and needs no treatment.
The first breath
The most important thing a new baby does is to take his or her first gasp of breath. In a healthy baby this will happen almost immediately and is usually more like a first cry. The baby may cry a lot when first born, or may settle quite quickly and breathe quietly. The normal breathing rate is between 30 and 40 breaths per minute. When these first gasps are taken, the baby’s circulation is undergoing extensive changes in the heart and blood vessels to adjust from the needs in the womb to the needs outside. The ductus arteriosus, which diverts blood past the lungs in the foetus, is no longer needed when the lungs expand to take in air and therefore disappears after birth. Other changes in the circulatory system of the newborn are that the umbilical vein becomes functionless, and that blood no longer passes through the foramen ovale, a hole between two atria of the heart. After birth this hole closes. These changes alter the blood circulation into the normal system, bringing into play the lungs for oxygen uptake, and separating the transport of oxygen-rich and oxygen-poor blood.
Occasionally heart murmurs can be heard in new babies because the foramen ovale takes some weeks to close. A new baby’s heart rate is much faster than an adult’s, beating 120 to 160 times per minute.