Your doctor will welcome any kind of call in which you have concerns about your newborn. There are times, however, when a more urgent call is necessary. St. Louis Children’s Hospital recommends you call your doctor right away if your baby is experiencing:

• 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/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 three to four 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 percent of birthweight is normal in the first two to three days after birth. However, the baby should have gained back to his/her birthweight by 10 or 11 days old. Signs a baby is not gaining weight may include a thin, drawn face, loose skin, and decreased number of wet or soiled diapers. Most physicians want to see a newborn in the office at the end of the first week to check his/her weight. Lack of weight gain or continued weight loss in a young baby may be a sign of illness or other conditions and needs to be treated.
    
    Feeding problems can be a sign of other conditions and may lead to serious illness if untreated. Consult your baby's physician if your baby has any difficulties taking or digesting feedings.
• Persistent Crying or Irritability
  All babies cry - this is their only way of communicating their needs to you. Babies also develop different types of cries for different needs - including hunger, sleepiness, loneliness, in need of a diaper change, and pain. At first, parents may not know how to interpret cries, but they usually can console a baby by meeting those needs. However, a baby who is continuously fretful and fussy, or cries for long periods, may be ill. Also, a baby may be very irritable if he/she is hurting. Colic, a common intestinal problem, can cause babies to cry inconsolably. Jitteriness or trembling may also be signs of illness.
  
  Examine your baby carefully to make sure there is not a physical problem - such as clothing pinching the baby, or a diaper pin sticking the baby. There may be a thread or even a hair tightly wound on a finger or toe. Look at the baby's abdomen for signs of swelling. Consult your baby's physician promptly if your baby is crying for longer than usual or has other signs of illness.