Premature birth is when ababy is born before the normal end ofpregnancy. In humans, a pregnancy normally lasts for about nine months or 266 days.
Babies who are born before 37 complete weeks of pregnancy (calculated from the lastmenstrual period) are said to bepremature. In theUnited States, about 12% of the babies are born prematurely (that is about one in every eight babies).[1] In 2003, there were over 490,000 premature births.
Worldwide rates of prematurity are more difficult to get. Indeveloping countries, there is often no professional medical care for these babies. This makes it difficult to tell how far along the pregnancy really was. For this reason, theWorld Health Organization tracks rates of lowbirth weight instead. In 2000, 16.5% of babies born in developing countries were of low birth weight.[2] About one-third of these low birth weight deliveries are due to premature delivery.
The risk of having a problem (called acomplication) is higher in shorter pregnancies. Babies born prematurely die more often in their first year of life than others. Most such deaths occur in the first month of life, which is calledneonatal mortality.
Worldwide, prematurity causes 10% of neonatal mortality, or around 500,000 deaths per year.[3] In the U.S., where manyinfections and other causes of neonatal death have been markedly reduced, prematurity is the leading cause of neonatal mortality at 25%.[4] Prematurely born infants are also at greater risk of developing serious health problems, such ascerebral palsy,chronic lung disease,gastrointestinal problems,mental retardation,vision loss, orhearing loss.[5] They are also more likely to havedepression as teenagers.[6]
Nearly half of all premature births haveno known cause. When conditions permit, doctors may attempt to stop premature labor, so that the pregnancy can have a chance to continue to full term. This will increase the baby's chances of health and survival.
In the United States, the rate of premature births has increased 30% in the past twodecades.[7]
In developed countries, manyhospitals have special facilities for prematurely born infants. This type of hospital unit is usually called aneonatal intensive care unit (NICU,pronounced "NICK-you"). In the NICU, premature babies are kept warm inincubators or other warming machines. They are enclosed in plastic with equipment which keeps them warm and keepsgerms away from them.
Modern neonatalintensive care involves sophisticated measurement oftemperature,respiration,heart function,oxygen supply, andbrain activity. Treatments may includefluids andnutrition given throughintravenouscatheters;oxygen,breathing support; andmedications.
In developing countries, where advanced equipment may not be available or reliable, simple measures such askangaroo care (skin-to-skin warming), encouragingbreastfeeding, and basic infection control measures help reduce death rate and illness.
The earliest time in the pregnancy where the infant has at least a 50% chance of survival is called thelimit of viability. In countries with good health care, viability has been reduced to about 24 weeks.[8][9] Rare survivors have been documented as early as 21 weeks,[10] but this date iscontroversial because the pregnancy was measured from the date of conception rather than the date of her mother's last menstrual period. This makesgestation appear 2 weeks less than if calculated by the more common method.[11] Risk ofbrain damage anddevelopmental delay is significant at that early time. Even if the infant lives, there areethical controversies over the care given to such infants. The limit of viability has also become a factor in theabortion debate.
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