When your baby was born, her birth weight included excess body fluid, which she lost during her first few days.
Most babies lose about one-tenth of their birth weight during the first five days, then regain it over the next five, so that by about day ten they usually are back to their original birth weight. Most babies grow very rapidly after regaining their birth weight, especially during growth spurts, which occur around seven to ten days and again between three and six weeks. The average newborn gains weight at a rate of 2⁄3 of an ounce (20–30 grams) per day and by one month weighs about ten pounds (4.5 kg). She grows between 1 1⁄2 and 2 inches (4.5 to 5 cm) during this month. Boys tend to weigh slightly more than girls (by less than 1 pound, or approximately 350 grams). They also tend to be slightly longer than girls at this age (by about 1⁄2 inch, or 1.25 cm).
Your pediatrician will pay particular attention to your child’s head growth, because it reflects the growth of her brain. The bones in your baby’s skull are still growing together, and the skull is growing faster during the first four months than at any other time in her life. The average newborn’s head circumference measures about 13 3⁄4 inches (35 cm), growing to about 15 inches (38 cm) by one month. Because boys tend to be slightly larger than girls, their heads are larger, though the average difference is less than 1⁄2 inch (1 cm).
During these first weeks your baby’s body gradually will straighten from the tightly curled position she held inside the uterus during the final months of pregnancy. She’ll begin to stretch her arms and legs and may arch her back from time to time. Her legs and feet may continue to rotate inward, giving her a bowlegged look. This condition usually will correct itself gradually over the first year of life. If the bowlegged appearance is particularly severe or associated with pronounced curving of the front part of the foot, your pediatrician may suggest a splint or a cast to correct it, but in most instances these circumstances are extremely unusual.
If your baby was born vaginally and her skull appeared misshapen at birth, it soon should resume its normal shape. Any bruising of the scalp or swelling of the eyelids that occurred during birth will be gone by the end of the first week or two. Any red spots in the eyes will disappear in about three weeks.
To your dismay, you may discover that the fine hair that covered your child’s head when she was born soon begins falling out. If she rubs the back of her head on her sleep surface, she may develop a temporary bald spot there, even if the rest of her hair remains. This loss is not medically significant. The bare spots will be covered with new hair in a few months.
Another normal development is baby acne—pimples that break out on the face, usually during the fourth or fifth week of life. They are thought to be due to stimulation of oil glands in the skin by hormones passed across the placenta during pregnancy. This condition may be made worse if the baby lies in sheets laundered in harsh detergents or soiled by milk that she’s spit up. If your baby does have baby acne, place a soft, clean receiving blanket under her head while she’s awake and wash her face gently once a day with a mild baby soap to remove milk or detergent residue.
Your newborn’s skin also may look blotchy, ranging in color from pink to blue. Her hands and feet in particular may be colder and bluer than the rest of her body. The blood vessels leading to these areas are more sensitive to temperature changes and tend to shrink in response to cold. As a result, less blood gets to the exposed skin, causing it to look pale or bluish. If you move her arms and legs, however, you should notice that they quickly turn pink again.
Your baby’s internal “thermostat,” which causes her to sweat when she’s too hot or shiver when she’s too cold, won’t be working properly for some time. Also, in these early weeks, she’ll lack the insulating layer of fat that will protect her from sudden temperature shifts later on. For these reasons, it’s important for you to dress her properly—warmly in cool weather and lightly when it’s hot. A general rule of thumb is to dress her in one more layer of clothing than you would wear in the same weather conditions. Don’t automatically bundle her up just because she’s a baby. Between ten days and three weeks after birth, the stump from the umbilical cord should have dried and fallen off, leaving behind a clean, well-healed area. Occasionally a raw spot is left after the stump is gone. It may even ooze a little blood-tinged fluid. Just keep it dry and clean (using a cotton ball dipped in rubbing alcohol) and it will heal by itself. If it is not completely healed and dry in two weeks, consult your pediatrician.