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What is prematurity?

A baby born before 37 weeks of pregnancy is considered premature. Slightly fewer than 12 percent of all babies are premature. Overall, the rate of premature births is rising, mainly due to the large numbers of multiple births in recent years. Twins and other multiples are about six times more likely to be premature than single birth babies. The rate of premature single births is slightly increasing each year. Other terms often used for prematurity are preterm and "preemie." Preterm generally refers to the pregnancy (as in preterm labor), while premature is more often used to describe your baby. Many premature babies also weigh less than 2,500 grams (5 .5 pounds) and may be referred to as low birthweight (LBW).

How Boston Children's approaches prematurity

Boston Children's is at the forefront of major research conducted on premature newborns. Boston Children's was one of the first hospitals to use gene-chip analyses to study diseases in premature newborns. Additionally, our specialized Growth and Nutrition Program at Boston Children's Hospital is specifically designed to help children with poor growth and feeding difficulties. And our NICU is routinely ranked as one of the best in the country.

Prematurity | Symptoms & Causes

What causes prematurity?

There are many factors that come into play when a baby is born prematurely. Some directly cause early labor and birth, while others can make the mother or baby sick and require early delivery. The following factors may contribute to a premature birth:

Maternal factors:

  • preeclampsia (also known as toxemia or high blood pressure of pregnancy)
  • chronic medical illness (such as heart or kidney disease)
  • infection (such as group B streptococcus, urinary tract infections, vaginal infections and infections of the fetal/placental tissues)
  • drug use (such as cocaine)
  • abnormal structure of the uterus
  • cervical incompetence (inability of the cervix to stay closed during pregnancy)
  • previous preterm birth

Factors involving the pregnancy:

  • abnormal or decreased function of the placenta
  • placenta previa (low lying position of the placenta)
  • placental abruption (early detachment from the uterus)
  • premature rupture of membranes (amniotic sac)
  • polyhydramnios (too much amniotic fluid)

Factors involving the fetus:

  • when fetal behavior indicates the intrauterine environment isn't healthy
  • multiple gestation (twins, triplets or more)

Why is prematurity a concern?

Premature babies are born before their bodies and organ systems have completely matured. These babies are often small, with low birthweight (less than 5 pounds), and they may need help breathing, eating, fighting infection and staying warm. Very premature babies who are born before 28 weeks, are especially vulnerable. Many of their organs may not be ready for life outside the mother's uterus and may be too immature to function well.

Some of the problems premature babies may experience include:

  • temperature instability - inability to stay warm due to low body fat
  • cardiovascular
    • patent ductus arteriosus (PDA) - a heart condition that causes blood to divert away from the lungs
    • too low or too high blood pressure
    • low heart rate - often occurs with apnea
  • blood and metabolic:
    • anemia - may require blood transfusion
    • jaundice - due to immaturity of liver and gastrointestinal function
    • too low or too high levels of minerals and other substances in the blood such as calcium and glucose (sugar)
  • gastrointestinal:
    • difficulty feeding - many are unable to coordinate suck and swallow before 35 weeks gestation
    • poor digestion
    • necrotizing enterocolitis (NEC) - a serious disease of the intestine common in premature babies
  • infections - premature infants are more susceptible to infection and may require antibiotics

How can I prevent prematurity?

Because of the tremendous advances in the care of sick and premature babies, more and more babies are surviving despite being born early and being very small. But prevention of early birth is the best way of promoting good health for babies.

Prenatal care is a key factor in preventing preterm births and low birthweight babies. At prenatal visits, the health of both mother and fetus can be checked. Because maternal nutrition and weight gain are linked with fetal weight gain and birthweight, eating a healthy diet and gaining weight in pregnancy are essential. Prenatal care is also important in identifying problems and lifestyles that can increase the risks for preterm labor and birth. Some ways to help prevent prematurity and to provide the best care for premature babies may include the following:  

  • identifying mothers at risk for preterm labor
  • prenatal education of the symptoms of preterm labor
  • avoiding heavy or repetitive work or standing for long periods of time which can increase the risk of preterm labor
  • early identification and treatment of preterm labor

Prematurity | Diagnosis & Treatments

What are the characteristics of a premature baby?

These are the most common characteristics of a premature baby. However, your baby may show different characteristics of the condition. Characteristics may include:

  • small baby, often weighing less than 2,500 grams (5 pounds 8 ounces)
  • thin, shiny, pink or red skin, able to see veins
  • little body fat
  • little scalp hair, but may have lots of lanugo (soft body hair)
  • weak cry and body tone
  • genitals may be small and underdeveloped

How we treat premature babies

Intensive care

Premature babies usually need care in a special nursery called the Neonatal Intensive Care Unit (NICU). Children's NICU combines advanced technology and specially trained doctors and nurses to care for the tiniest patients. Our NICU team is led by a neonatologist, who is a pediatrician with additional training in the care of sick and premature babies.

Corticosteroid medication

One of the most important parts of care for premature babies is a medication called a corticosteroid. Research has found that giving the mother a steroid medication at least 48 hours prior to delivery greatly reduces the incidence and severity of respiratory disease in your baby.

Another major benefit of steroid treatment is lessening of intraventricular hemorrhage (bleeding in your baby's brain). Although studies are not clear, prenatal steroids may also help reduce the incidence of NEC and PDA. Mothers may be given steroids when preterm birth is likely between 24 and 34 weeks of pregnancy. Before that time, or after, the medication usually isn't effective.

Care of premature babies may also include:

  • temperature-controlled beds
  • monitoring of temperature, blood pressure, heart and breathing rates and oxygen levels
  • giving extra oxygen by a mask or with a breathing machine
  • mechanical ventilators (breathing machines) to do the work of breathing for your baby
  • intravenous (IV) fluids - when feedings cannot be given, or for medications
  • placement of catheters (small tube) into the umbilical cord to give fluids and medications and to draw blood
  • x-rays (for diagnosing problems and checking tube placement)
  • special feedings of breast milk or formula, sometimes with a tube into the stomach if a baby cannot suck
  • medications and other treatments for complications, such as antibiotics
  • kangaroo care - a method of caring for premature babies using skin-to-skin contact with the parent to provide contact and aid parent-infant attachment

When can a premature baby go home from the hospital?

Your baby will likely need time to "catch up" in her development and growth. In the hospital, this catch-up time may involve learning to eat and sleep, as well as steadily gaining weight. Depending on her condition, your baby may need to stay in the hospital until they she reaches the mother's due date.

General goals for discharge may include:

  • serious illnesses are resolved
  • stable temperature - able to stay warm in an open crib
  • taking all feedings by breast or bottle
  • no recent apnea or low heart rate
  • parents are able to provide care including medications and feedings

Before you leave the hospital, your baby will need an eye examination and hearing test to check for problems related to prematurity.

Even though they are otherwise ready for discharge, some babies continue to have special needs, such as extra oxygen or tube feedings. With instruction and the right equipment, these babies are often able to be cared for at home by parents. Our social workers can help coordinate discharge plans when special care is needed.

Ask your physician about a "trial run" overnight stay in a parenting room at the hospital before your baby is discharged. This can help you adjust to caring for your baby while doctors and nurses are nearby for help and reassurance. You may also feel more confident taking their baby home when they have been given instructions in infant CPR (cardiopulmonary resuscitation) and infant safety.

Prematurity | Research & Clinical Trials

Premature infants and ventilators

Premature babies often need to be placed on ventilators, but these life-saving machines can sometimes damage their delicate lungs. In recent experiments in mice, stem cells taken from bone marrow and injected into the blood provided partial protection: the lungs' blood vessels were better maintained and inflammation was reduced.

Even when fluid in which the cells (known as bone marrow stromal cells) were grown was able to protect the lungs — in fact, better than the stem cells themselves. Stella Kourembanas, MD, former chief of Boston Children's Division of Newborn Medicine, believe this fluid, or certain proteins her lab has isolated within it, could become a future treatment to prevent preemies from developing chronic lung disease. She would also like to conduct follow-up experiments using stem cells taken from the umbilical cord, which can be obtained from infants in a less invasive manner than bone marrow cells.

Memantine and infant brains

Up to 35 percent of babies who survive prematurity are left with brain damage leading to cerebral palsy and cognitive/behavioral deficits. Now, neuroscientist Frances Jensen, MD, with Simon Manning, MD and Delia Talos, MD, in the Department of Neurology and the Neurobiology Program, reports that memantine (Namenda), a drug originally developed for Alzheimer's disease, may reduce the damage.

For more than a decade, Jensen and others at Children's have shown that premature newborns rapidly developing brains have unique characteristics that not only heighten their vulnerability to hypoxia-ischemia (a common complication of prematurity that compromises the brains blood and oxygen supply), but also prevent these infants from responding to existing neurologic drugs. But Jensen has been finding new targets unique to the newborn brain — as well as drugs that can hit them, some of them already FDA-approved.

In the Journal of Neuroscience, Jensen's team shows that preterm infants oligodendrocytes, the cells that form the brains white matter, are especially rich in NMDA receptors, a type of glutamate receptor. After a hypoxic-ischemic insult, glutamate builds up and can over-activate NMDA receptors, producing a pattern of white-matter injury known as periventricular leukomalacia (PVL), the most common cause of cerebral palsy.

However, working with a rat model of PVL, Jensen and colleagues found that giving memantine — which acts by blocking the NMDA receptor — significantly reduced white-matter injury after a hypoxic-ischemic insult. Back in the 1990s, Boston Children's participated in memantines development as a treatment for Alzheimer's disease. Now, if Jensen can establish the drugs safety in premature newborns, she wants to test it as a protective therapy.

Prematurity and autism

Extremely premature infants are known to have a high prevalence of learning disabilities and attention and behavioral problems. Premature infants born at less than 3.3 pounds have an increased risk for showing early signs of autistic characteristics, according to a Boston Children's Hospital study. "Early screening for autistic features might be warranted in this population," says researcher Catherine Limperopoulos, PhD, who cautions against drawing conclusions. "By no means are we suggesting all premature babies are at risk for autism.

Alternative ventilation for premature infants

Bernadette Levesque, MD, of the Division of Newborn Medicine led a study showing that mechanical ventilators can be hard on an infant’s lungs, and instead, encourage the use of “bubble” continuous positive airway pressure (bCPAP) system, which delivers a warmer, humidified oxygen that’s more gentle on an infant’s lungs.

Prematurity | Programs & Services