Low Birth Weight

Low birth weight refers to infants who weigh less than 5.5 pounds at birth. Most normal babies weigh 5.5 pounds by 37 weeks of gestation. Intrauterine growth restriction refers to delayed growth within the uterus, which then leads to low birth weight. Some babies are just small and happen to weigh less than 5.5 pounds at birth. Though this is considered low birth weight, in these cases, it is not abnormal or a cause for concern.

Low birth weight

Low birth weight may be suspected before delivery if the size of the mother's uterus is small, or if a small fetus is shown by ultrasound. The fetus may appear symmetrically small, or have a head that is of normal size for gestational age but an unusually small abdomen. Although the overall size of the fetus or infant is small, the organ systems are appropriately mature for gestational age. If the mother is small, it may be normal for her to have a small fetus.



Several factors can cause delayed growth of a fetus. Babies with congenital anomalies or chromosomal abnormalities are often associated with low birth weights. Sometimes problems with the placenta can prevent it from providing adequate oxygen and nutrients to the fetus. Infections during pregnancy that affect the fetus, such as rubella, cytomegalovirus, toxoplasmosis, and syphilis, may also affect the baby's birth weight. Risk factors in the mother that may contribute to low birth weight include multiple pregnancies, previous low birth-weight infants, poor nutrition, heart disease or hypertension, smoking, drug addiction, alcohol abuse, lead exposure, and insufficient prenatal care. Low birth weight is more common in first-time pregnancies and among pregnant women under the age of 17 and over the age of 35.



The infants that weigh less than 2500 grams or less are at a greater risk of death within the first month of life, as well as increased risk for developmental disabilities and illness throughout their life. Lifelong problems include chronic lung disease, adult-onset diabetes, coronary heart disease, high blood pressure, intellectual, physical and sensory disabilities, and psychological and emotional distress. Very low birth weight infants are also at higher risk for SIDS, or Sudden Infant Death Syndrome.



How Is Low Birth Weight Identified?



Prenatal care is very important since few women carrying infants with delayed growth experience any symptoms. The most common symptom is simply a feeling that the baby is not as big as it should be. Because of this lack of symptoms, your health care provider should carefully measure your abdomen during each prenatal visit. If the measurements do not increase sufficiently over time, a follow-up exam will most likely include an ultrasound. The ultrasound can determine more precisely the gestational age of your baby and whether or not there is intrauterine growth restriction.


Low birth rate is also determined when your newborn is examined after delivery. If your baby's weight and length fall below the 10th percentile for his age, then he is considered to be low birth weight.



Is Low Birth Weight Treatable?



While there is no specific treatment, it is very important to maintain adequate nutrition during pregnancy for you and the fetus, and for your infant once he is born. In some cases, risk factors that may lead to low birth weight can be identified early on in the pregnancy and be reduced or eliminated through behavioral changes and treatment of chronic conditions. Most low birth-weight infants eventually catch up with the growth of other babies their age somewhere between the 18th and 24th month.


A number of complications may occur if your infant has experienced intrauterine growth restriction. A lack of oxygen during the birthing process, called birth asphyxia, may occur if the growth restriction is caused by problems with the placenta. Meconium aspiration (aspiration of amniotic fluid that is contaminated with the infant's first stool) may occur as a result of stress during delivery. There may also be low blood glucose levels during the first hours or days of life.
It’s hard for a mother to tell if she’s carrying a smaller-than-normal fetus, particularly it’s your first pregnancy. Nevertheless, call your health care provider if you are pregnant and your baby seems very small. You should also call if your infant or child does not seem to be growing or developing at a standard rate.



Prevention



Although there are no proven prevention strategies, there are a few things you can do to increase your chances of giving birth to a baby with healthy weight. Proper nutrition, adequate rest, and avoidance of cigarettes, drugs, and alcohol will contribute to the development of a healthier child.

Low birth weight

What can a mom do to prevent low birth weight?



There is general agreement among pediatricians, the March of Dimes, American Heart Association, and local and state health professionals that drinking, smoking and using drugs during pregnancy negatively impact the size and health of a newborn. Lack of pre-natal care and poor pre-natal nutritional habits also play a role. Some studies have also shown that having a previous low birth weight baby or multiple births, or unplanned pregnancy, and a mother being over 35 can contribute to having a low birth weight infant. There is also concern that environmental factors, stress, racism and poverty contribute to the terribly high rate, of 13.1% low birth weight infants, among African American mothers.

• No drinking, smoking or using drugs during pregnancy
• Healthy food during pregnancy
• Regular pre-natal check-ups

Other ways of getting the best possible outcome for you and your infant are avoiding stress, developing relaxation techniques, and maintaining a health weight. An important element of pre-pregnancy is taking a multivitamin with 400 mcg of folic acid every day, to avoid neural tube defects in your baby.




PROBLEMS OF LOW-BIRTH-WEIGHT INFANTS

Low birth weight

•Low-birth-weight, premature babies are more likely to have underdeveloped lungs and
breathing problems. Extremely premature babies (under 28 weeks) also can have heart
problems that can lead to heart failure.


• Very low-birth-weight babies (less than 3 pounds, 5 ounces or 1,500 grams at birth) can
develop bleeding in the brain, leading to learning or behavioral problems later in life.


• The liver may be immature and not function properly.


• Anemia (too few red blood cells) or polycythemia (too many red blood cells) also can occur.


• Often, low-birth-weight babies do not have enough body fat and have trouble
maintaining normal body temperature.


• Feeding problems may occur, and risk of infection may be increased.




PREVENTING LOW BIRTH WEIGHT




• Have regular checkups throughout your pregnancy.


• Eat a balanced diet high in fiber and low in fat.


• Consume sufficient calories, vitamins, and minerals, including at least 400 micrograms of
the B vitamin folic acid every day.


• Gain a healthful amount of weight during pregnancy—the recommended amount is 25
to 35 pounds.


• Stop smoking and stay away from tobacco smoke during pregnancy.


• Do not use alcohol or other drugs, including herbal preparations, unless they are
prescribed by your doctor.


Although a serious and potentially life-threatening condition, low birth weight can often be
treated. Your baby might have to stay in the hospital longer to be treated and until he or
she gains sufficient weight. Medications can help correct or improve many low-birth-weight
problems, and there are devices and medicines to help the baby breathe more easily during
the critical early days of life.

Why are babies born with low birthweight?



There are two main reasons why a baby may be born with low birthweight:

• Premature birth: Babies born before 37 completed weeks of pregnancy are called premature or preterm. About 67 percent of low-birthweight babies are premature . The earlier a baby is born, the less it is likely to weigh and the less developed its organs will be. Very low-birthweight babies (those who weigh less than 3 pounds, 5 ounces or 1,500 grams) have the highest risk of health problems. Some premature babies born near term do not have low birthweight, and they may have only mild or no health problems as newborns.

• Small-for-date babies (also called small-for-gestational age or growth-restricted): These babies may be full-term but are underweight. Some of these babies are healthy, even though they are small. They may be small simply because their parents are smaller than average. Others have low birthweight because something slowed or halted their growth in the uterus.

Some babies are both premature and growth-restricted. These babies are at high risk for health problems.

What causes low birthweight?



Preterm labor frequently results in the birth of a premature, low-birthweight baby. The causes of preterm labor are not thoroughly understood. However, we do know that women with these risk factors are at increased risk of delivering prematurely :

• Had a premature baby in a previous pregnancy 
• Are pregnant with twins or other multiples 
• Have certain abnormalities of the uterus or cervix

Other factors that may contribute to premature birth and/or fetal growth restriction include:

• Birth defects: Babies with certain birth defects are more likely to be small for date because genetic conditions or environmental factors may limit normal development .
  
• Chronic health problems in the mother: Maternal high blood pressure, diabetes, heart, lung and kidney problems sometimes can reduce birthweight .
  
• Smoking: Pregnant women who smoke cigarettes are nearly twice as likely to have a low-birthweight baby as women who do not smoke . Smoking slows fetal growth and increases the risk of premature delivery .
  
• Infections in the mother: Certain infections, especially those involving the genito-urinary tract, may increase the risk of preterm delivery .
  
• Infections in the fetus: Infection with certain viruses, including cytomegalovirus, rubella and chickenpox, can slow fetal growth and cause birth defects .
  
• Alcohol and illicit drugs: Alcohol and illicit drugs can limit fetal growth and can cause birth defects. Some drugs, such as cocaine, also may increase the risk of premature delivery.
  
• Placental problems: Placental problems can reduce flow of blood and nutrients to the fetus, limiting growth. In some cases, a baby may need to be delivered early to prevent serious complications in mother and baby.
  
• Inadequate maternal weight gain: Women who gain too few pounds during pregnancy increase their risk of having a low-birthweight baby. Women of normal weight should usually gain 25 to 35 pounds during pregnancy.
  
• Socioeconomic factors: Low income and lack of education are associated with increased risk of having a low-birthweight baby, although the underlying reasons for this are not well understood. Black women and women under 17 and over 35 years of age are at increased risk .

What can a woman do to reduce her risk of having a low birthweight baby?

There are some steps a woman can take to reduce her risk of having a low-birthweight baby. A woman who is planning pregnancy should see her health care provider for a pre-conception check-up. Her provider can help make sure she is as healthy as possible before she conceives. At this visit the provider can screen her for certain infections, make sure her vaccinations are up-to-date, and discuss her health habits and nutrition.

The provider can make sure any medications the woman takes are the safest possible choices during pregnancy. A preconception visit is especially important for women with chronic health conditions, such as high blood pressure and diabetes. Good control of these disorders, starting before pregnancy, reduces the risk of low birthweight and other pregnancy complications.

A woman should stop smoking before she becomes pregnant and remain smoke-free throughout pregnancy. At a preconception visit, a woman's health care provider can refer her to a smoking-cessation program or suggest other ways to help her quit.

Once a woman is pregnant, she should get early and regular prenatal care. When women receive adequate prenatal care, health care providers can identify many problems early. This allows treatment that may reduce the risk of having a low-birthweight baby.

All women who could become pregnant should take a daily multivitamin containing 400 micrograms of folic acid, starting before pregnancy. When taken before and early in pregnancy, folic acid helps prevent certain serious birth defects of the brain and spine. When taken throughout pregnancy, folic acid also may help reduce the risk of having a premature and low-birthweight baby .

A woman who suspects that she is developing preterm labor should call her health care provider immediately. Her provider may want to examine her and do some tests to see if she really is in labor. If she is in labor, the provider may give her a medication (called a tocolytic) to try to delay or stop delivery. These drugs are most effective when given early in labor. Tocolytics often postpone delivery for only a day or two, but even such a short delay can make a difference in the baby's health.

Women who have already had a premature baby may benefit from treatment with a hormone called progesterone. Recent studies show that this treatment appears to reduce their risk of having another premature baby by about one-third .

How is fetal growth restriction treated?

About 10 percent of fetuses are considered growth-restricted. A health care provider may suspect fetal growth restriction if the mother's uterus is not growing at a normal rate. This can be confirmed with a series of ultrasound examinations that monitor how quickly the fetus is growing. In some cases, fetal growth can be improved by treating any condition in the mother (such as high blood pressure) that may be a contributing factor.

The provider will closely monitor the well-being of a growth-restricted fetus using ultrasound and fetal heart rate monitoring. If these tests show that the baby is having problems, the baby may need to be delivered early.

What medical problems are common in low-birthweight babies?

Low-birthweight babies are more likely than babies of normal weight to have health problems during the newborn period. Many of these babies require specialized care in a neonatal intensive care unit (NICU). Serious medical problems are most common in babies born at very low birthweight.

• Respiratory distress syndrome (RDS): About 23,000 babies a year—most of whom were born before the 34th week of pregnancy—suffer from this breathing problem. Babies with RDS lack a protein called surfactant that keeps small air sacs in the lungs from collapsing. Treatment with surfactant helps affected babies breathe more easily. Babies with RDS also may need additional oxygen and mechanical breathing assistance to keep their lungs expanded. The sickest babies may temporarily need the help of a respirator to breathe for them while their lungs mature.
  
• Bleeding in the brain (called intraventricular hemorrhage or IVH): Bleeding in the brain occurs in some very low- birthweight babies, usually in the first three days of life. Brain bleeds usually are diagnosed with an ultrasound examination. Most are mild and resolve themselves with no or few lasting problems. More severe bleeds can cause pressure on the brain that can lead to brain damage. In such cases, surgeons may insert a tube into the brain to drain the fluid and reduce the risk of brain damage. In milder cases, drugs sometimes can reduce fluid buildup.
  
• Patent ductus arteriosus (PDA): PDA is a heart problem that is common in premature babies. Before birth, a large artery called the ductus arteriosus lets the blood bypass the baby's nonfunctioning lungs. The ductus normally closes after birth so that blood can travel to the lungs and pick up oxygen. When the ductus does not close properly, it can lead to heart failure. PDA can be diagnosed with a specialized form of ultrasound (echocardiography) or other imaging tests. Babies with PDA are treated with a drug that helps close the ductus, although surgery may be necessary if the drug doesn't work.
  
• Necrotizing enterocolitis (NEC): This potentially dangerous intestinal problem usually develops two to three weeks after birth. It can lead to feeding difficulties, abdominal swelling and other complications. Babies with NEC are treated with antibiotics and fed intravenously (through a vein) while the bowel heals. In some cases, surgery is necessary to removed damaged sections of intestine.
  
• Retinopathy of prematurity (ROP): ROP is an abnormal growth of blood vessels in the eye that can lead to vision loss. It occurs mainly in babies born before 32 weeks of pregnancy. Most cases heal themselves with little or no vision loss. In severe cases, the ophthalmologist (eye doctor) may treat the abnormal vessels with a laser or with cryotherapy (freezing) to preserve vision.

Can medical problems in low-birthweight, premature newborns be prevented?

When a provider suspects that a woman may deliver before 34 weeks of pregnancy, she may suggest treating the mother with corticosteroid drugs. Corticosteroids speed maturation of the fetal lungs and significantly reduce the risk of RDS, IVH, necrotizing enterocolitis and infant death. These drugs, which are given by injection (a shot), are most effective when administered at least 24 hours before delivery. Treatment with tocolytic drugs to delay labor can give the health care provider time to treat the pregnant woman with corticosteroids. The provider also can arrange for delivery in a hospital with a NICU that can give specialized care to a premature, low-birthweight infant.