Prematurity is the leading cause of abnormalities and death in newborns. Some organs in the infant may not be fully developed so that the baby has a higher risk of developing certain diseases.

Prematurity is a condition found in immature infants when gestational age was 37 weeks yet. The causes of preterm birth are generally not known. However, 15% of preterm births are found in multiple pregnancy (in utero there is more than one fetus).
The factors that contribute to the onset of preterm labor are:

Pregnancy at a young age (maternal age less than 18 years old)
Irregular prenatal care
Lower socio-economic groups
Nutritional state less
Drug abuse
The problems in the mother that the cause of the prematurity may include:

History of preterm birth in a previous pregnancy
High levels of alpha-fetoprotein during the second trimester of unknown cause
Disease or untreated infections (eg, urinary tract infection or infection of the membranes)
Abnormalities in the uterus or cervix
Premature rupture of the membranes
Placenta previa (placenta covering the cervix)
Pre-eclampsia (a condition that commonly occurs in the second trimester of pregnancy characterized by high blood pressure, protein in the urine, and swelling of the limbs)
Heart disease
Diabetes mellitus
Keep in mind, the physical symptoms of preterm infants, ie:

Smaller body size
Low birth weight (less than 2.5 kg)
His skin is thin, light, and pink (opaque)
Veins visible under the skin (transparent skin)
Little fat under her skin so skin looks wrinkled
The hair is sparse
Ears thin and flabby
Weak cry
Relatively large head
Weak muscles and little physical activity (a premature baby tend to not have a line of hand or foot as in infants born at term)
Reflex sucking and swallowing reflexes are bad
Irregular breathing
Scrotal sac and a tiny little pleats (the boys)
Not cover the labia majora labia minora (in girls)
The lungs are mature very important for newborns. To be able to breathe freely, when the baby is born, the air sacs (alveoli) must be filled by air and keep it open. Alveoli will open wide because of the presence of a substance called surfactant, which is produced by the functioning of the lungs and lowers the surface tension. Premature babies often do not produce sufficient amounts of surfactant, so alveolinya not stay open. In between times he was breathing, his lungs completely deflated, resulting in Respiratory Distress Syndrome. The syndrome can lead to other disorders and in some cases can be fatal.

Immaturity of the central nervous system can cause the baby to suck or impaired swallowing reflex and prone to the occurrence of brain hemorrhage. Besides lungs underdeveloped, preterm infants also have underdeveloped brains. This can cause apnea (breathing stops), because the respiratory center in the brain may not have been mature.

Immaturity of the digestive system causing feeding intolerance. At first, the small size of the stomach may be limiting the amount of food or liquid that is given, thus feeding the baby too much can cause vomiting.

After birth, the baby needs liver function and normal bowel function to dispose of bilirubin (a pigment yellow breakdown product of red blood cells) in the stool.