Premature Birth Statistics

Definitions

• Premature born before 37 weeks
• Moderately premature born between 35 and 37 weeks
• Very premature born between 29 and 34 weeks
• Extremely premature born between 24 and 28 weeks
• Low birthweight baby weighs less than 2,500 g (5.5 lbs)
• Very low birthweight baby weighs less than 1,500 g (3.0 lbs)
• Extremely low birthweight baby weighs less than 1,000 g (2.2 lbs)
• Neonatal deaths = within 28 days of birth
• Prenatal deaths = stillbirths and deaths occurring within the 1st week of life

Survival Rates

• Babies born at 23 weeks have a 17% chance of survival
• Babies born at 24 weeks have a 39% chance of survival
• Babies born at 25 weeks have a 50% chance of survival
• From 32 weeks onwards, most babies are able to survive with the help of medical Technology [EPICure data]

Outcomes

• 1 in 10 premature babies will develop a permanent disability such as lung disease, cerebral palsy, blindness or deafness.
• 50% of premature babies born before the 26th week of gestation are disabled, a quarter severely so. (Fowler GA. Preemie problems: the sobering statistics. US News World Reports 2000; vol 129: pp56.)
• Of children born before 26 weeks' gestation, results in 241 of the surviving children at six years (early school age) indicate a high level of disability as follows:
  • 22% severe disability (defined as cerebral palsy but not walking, low cognitive scores, blindness, profound deafness)
  • 24% moderate disability (defined as cerebral palsy but walking, IQ/cognitive scores in the special needs range, lesser degree of visual or hearing impairment)
  • 34% mild disability (defined as low IQ/cognitive score, squint, requiring glasses)
  • 20% no problems
• This study also showed a greater risk of severe disability and lower cognitive function results for boys compared with girls. This supports the theory that male sex is an important risk factor in extremely preterm infants.
• Cognitive and neurological impairment is common at school age amongst extremely preterm children. [N Engl J Med 2005; 352: 9-19.] Epicure data

Preterm Labor and Birth

Preterm labor (also called premature labor) is labor that begins before 37 weeks of pregnancy.  Because the fetus is not fully grown at this time, it may not be able to survive outside the womb.  Health care providers will often take steps to try to stop labor if it occurs before this time.

A baby born before 37 weeks of pregnancy is considered a preterm birth (or premature birth).  Preterm births occur in about 12 percent of all pregnancies in the U.S.  It is one of the top causes of infant death in this country.

Who is at risk for preterm labor and birth?

Health care providers currently have no way of knowing which women will experience preterm labor or deliver their babies preterm.  But there are factors that place a woman at higher risk for preterm labor or birth:

• Certain infections, such as bacterial vaginosis and trichomoniasis
• Shortened cervix
• Previously given birth preterm

Premature infants may face a number of health challenges, including:

• Low birth weight
• Breathing problems because of underdeveloped lungs
• Underdeveloped organs or organ systems
• Greater risk for life-threatening infections
• Greater risk for a serious lung condition, known as respiratory distress syndrome
• Greater risk for cerebral palsy (CP)
• Greater risk for learning and developmental disabilities

They may need to stay in the hospital for several weeks or more, often in a neonatal intensive care unit (NICU).

What methods are used to prevent preterm delivery?

Research supported by the NICHD found that treating high-risk pregnant women (those who have previously had a spontaneous preterm baby) with a certain type of progesterone reduces the risk of another preterm delivery. The treatment worked among all ethnic groups in the study and improved outcomes for the babies. Efforts to find out whether the treatment works for other at-risk women, such as those having twins and triplets, are ongoing. Bed rest and medications that relax the muscles in the uterus are also commonly used to try to stop preterm labor. 

Researchers have found that other methods of stopping preterm labor are not as effective as once thought.  For instance, NICHD-supported researchers have found that home uterine monitors are not effective for predicting or preventing preterm labor.

In addition, NICHD-funded research found that screening women who don’t show any symptoms of infection, but who have bacterial vaginosis, and treating them with antibiotics did not prevent preterm birth.

Records

James Elgin Gill (born on 20 May 1987 in Ottawa, Canada) was the earliest premature baby in the world. He was 128 days premature (21 weeks and 5 days gestation) and weighed 1 lb. 6 oz. (624 g). He survived and is quite healthy.

Amillia Taylor is also often cited as the most-premature baby. She was born on 24 October 2006 in Miami, Florida, at 21 weeks and 6 days gestation. At birth she was 9 inches (23 cm) long and weighed 10 ounces (283 grams). She suffered digestive and respiratory problems, together with a brain hemorrhage. She was discharged from the Baptist Children's Hospital on 20 February 2007.

The record for the smallest premature baby to survive was held for some time by Madeline Mann, who was born at 26 weeks weighing 9.9 oz (280 g) and 9.5 inches (24 cm) long. This record was broken in September 2004 by Rumaisa Rahman, who was born in the same hospital at 25 weeks gestation. At birth she was eight inches (20 cm) long and weighed 244 grams (8.6 ounces). Her twin sister was also a small baby, weighing 563 grams (1 pound 4 ounces) at birth. During pregnancy their mother had suffered from pre-eclampsia, which causes dangerously high blood pressure putting the baby into distress and leading to birth by caesarean section. The larger twin left the hospital at the end of December, while the smaller remained there until 10 February 2005 by which time her weight had increased to 1.18 kg (2 pounds 10 ounces). Generally healthy, the twins had to undergo laser eye surgery to correct visual problems, a common occurrence among premature babies.

Historical figures who were born prematurely include Johannes Kepler (born in 1571 at 7 months gestation), Isaac Newton (born in 1643, small enough to fit into a quart mug, according to his mother), Winston Churchill (born in 1874 at 7 months gestation), and Anna Pavlova (born in 1885 at 7 months gestation).

Mortality and Morbidity

Mortality is the rate of death or the number of premature babies admitted to an NCIU who do not survive compared to those who do. As noted above, the mortality rate of premature babies has dramatically improved over the last 20 years or so. The overwhelming majority of babies with access to the modern technology and medical techniques available in the NICU now survive. At the same time, there are limits to the medical technology and techniques available in the NICU; some babies who are born too soon are too small to either save at all or save without serious disability or morbidity.

Morbidity is the number of babies who survive but with lasting complications, compared to the number who survive with no lasting complications. In other words, the morbidity rate is the number of premature babies who grow up with medical, developmental, or psychological problems compared to those who grow up without any of these issues. Although many premature babies go on to live normal, healthy lives, the success rate in this regard is not as overwhelming as the dramatic improvement in mortality. In fact, the two statistics are related: medicine has become very successful at keeping premature babies alive, especially the extremely premature, who tend to have more complications than other premature babies.

Mild, Moderate, and extreme Prematurity

In general, outcomes are related to the gestational age, or the number of weeks a premature baby spent in the womb, and the weight of the baby at birth.

The Spectrum of Prematurity

Based on their gestational age and birth weight, premature babies are placed into loosely defined categories of mild, moderate, and extreme prematurity.

• Mild prematurity refers to babies who are born between 33 and 36 completed weeks gestational age and/or have a birth weight between 1500 and 2500 g (between about 3 lbs 5 oz and 5 lbs 8 oz).
• Moderate prematurity refers to babies who are born between 28 and 32 completed weeks gestational age with a birth weight ranging between 1000 and 1500 g (between about 2 lbs 3 oz and 3 lbs 5 oz).
• Extreme prematurity refers to babies who are born before 28 completed weeks gestational age or who have a birth weight of less than 1000 g (less than about 2 lbs 3 oz).

Mildly premature babies do better than moderately premature babies, who in turn do better than extremely premature babies. This makes intuitive sense: barring other complications not due to prematurity, the longer a baby has spent in the womb, the more developed her organs are and therefore the more prepared she is for the challenges of the outside world.

Statistics and the individual baby

As specific complications are addressed in this site, outcome statistics specific to that condition are provided where appropriate. However, mortality and morbidity statistics are based on group data and do not take into account the individual baby. The body is very much an interconnected system. The ways in which two or more complications affect each other can have a huge impact on morbidity and mortality, making the course and outcomes of illness difficult to predict.

Some, though few, extremely premature babies do surprisingly well and go on to thrive as healthy children. Conversely, some mildly premature babies who are expected to do well develop complications and lifelong problems or do not survive at all.

This is not to say that statistics and outcome data should be ignored; this information is extremely useful to physicians and other medical professionals who are devoted to producing the best possible outcomes for premature babies. Mortality and morbidity data can help medical staff anticipate and predict problems that have not surfaced yet, allowing for pre-emptive or preventative treatment that will benefit the baby.

Outcome statistics are not definitive. Rather, they are a guide to be used by medical professionals, and parents and families. Given all the possible combinations of complications premature babies may face, making an actual outcome prediction can be complex, even impossible. At other times, a particular complications or series of complications may make outcome prediction, both good and poor, more simple. For this reason, staff at the NICU will speak in terms of probabilities: for example, they may say that 75% of babies with a specific condition will recover completely without lifelong complications. Predicting an individual baby’s outcome cannot be done with absolute certainty.