Jitteriness, irritability, and lethargy are all signs of in a newborn.

A change in behavior may be one of the first signs of illness in a newborn. Although a baby's activity level, appetite, and cries normally vary from day to day, even hour to hour, a distinct change in any of these areas may signal illness.

Generally, if your baby is alert and active when awake, is feeding well, and can be comforted when crying, occasional differences in these areas are normal. Consult your baby's doctor if you have concerns about your baby's behavior. Some behavior changes may indicate an illness is present, including the following:

• Listlessness or lethargy. Lethargic or listless babies appear to have little or no energy, are drowsy or sluggish, and may sleep longer than usual. They may be hard to wake for feedings and even when awake, are not alert or attentive to sounds and visual stimulation. Sometimes, this can develop slowly and a parent may not notice the gradual change. Lethargy may be a sign of infection or other condition, such as low blood glucose (sugar). Consult your baby's doctor if your he or she becomes lethargic or has a change in activity level.

• Poor feeding. Feeding problems may include difficulty with a baby's suck at the breast or bottle, lack of hunger, problems with spitting up, and weight loss.

  • Feeding difficulties due to a sucking problem may show up when a baby starts out at birth with a strong, vigorous suck and gradually become less effective at feedings over time, or when a baby starts out with a weak suck and does not eat effectively. This is especially common if he or she was born prematurely. Babies with a weak suck may not pull strongly or have a good latch while breastfeeding. The mother may not hear the baby swallowing or gulping during feedings. A mother's breasts may not feel full right before a feeding or she may not notice her breasts getting softer (emptying) after a feeding. Bottle-fed babies with a weak suck may need the bottle nipple "worked" or pumped to stimulate a suck. Feedings with either breastfed or bottle-fed babies with a weak suck may take a very long time, often more than 45 minutes.

  • After the first day or so, most newborns are ready to eat every 3 to 4 hours and show signs of hunger by sucking on fingers or a hand, crying, and making rooting motions. A sick baby may refuse feedings. A baby who sleeps continuously and shows little interest in feeding may be ill.

  • Spitting up and dribbling milk with burps or after feedings is fairly common in newborns. This is because the sphincter muscle between the stomach and the esophagus (the tube from the mouth to stomach) is weak and immature. However, forceful or projectile vomiting, or spitting up large amounts of milk after most feedings, can indicate a problem. In formula-fed babies, vomiting may occur after overfeeding, or because of an intolerance to formula. In breastfed or formula-fed babies, a physical condition that prevents normal digestion may cause vomiting. Discolored or green-tinged vomit may mean the baby has an intestinal obstruction.

  • Weight loss up to about 10% of birthweight is normal in the first 2 to 3 days after birth. However, the baby should reach his or her birthweight by 10 or 11 days old. Signs a baby is not gaining weight may include a thin, drawn face, loose skin, and a decreased number of wet or soiled diapers. Most doctors want to see a newborn in the office at the end of the first week to check his or her weight. Lack of weight gain or continued weight loss in a young baby may be a sign of illness or other conditions that need to be treated.

    Feeding problems can be a sign of other conditions and may lead to serious illness if untreated. Consult your baby's doctor if your baby has any difficulties taking or digesting feedings.