As 10 principais causas de bebês com baixo peso ao nascer

Mesmo quando um bebê vem ao mundo com 3,5 quilos, os pais se preocupam com sua vulnerabilidade. Essa preocupação é agravada para os pais de prematuros - bebês minúsculos pesando 5 libras, 8 onças ou menos, normalmente nascidos antes de 37 semanas.

Cerca de um em cada 12 bebês norte-americanos nasce com baixo peso ao nascer, o que acarreta o risco de infecção, atrasos no desenvolvimento e até morte, de acordo com o March of Dimes. De fato, o número de bebês nascidos durante o período pré-termo tardio de 34 a 36 semanas aumentou 20% desde 1990, de acordo com os Centros de Controle e Prevenção de Doenças dos EUA.

Aqui nós o guiamos pelas várias causas do baixo peso ao nascer na esperança de que uma maior compreensão do problema possa ajudar na sua prevenção, começando com o número 1 de baixo risco de natalidade: gravidez múltipla.

1. Gravidez múltipla
2. Doenças e Infecções Maternas
3. Fumar
4. Álcool e drogas
5. Problemas com o útero ou colo do útero
6. Mau funcionamento placentário
7. Nutrição pobre
8. Estresse
9. Defeitos de nascença
10. Infecções Fetais

Quando uma mulher carrega mais de um bebê, seu risco de parto prematuro dispara. Cada bebê adicional aumenta o risco significativamente: as taxas de pré-termo são de aproximadamente 60% para gêmeos, 90% para trigêmeos e cerca de 100% para quadrigêmeos e além.

Por que o aumento dramático do risco? Bebês adicionais esticam o útero e competem por nutrientes limitados. Gestações múltiplas também sobrecarregam o corpo da mãe, às vezes levando a complicações como anemia, pressão alta e parto prematuro, de acordo com o Congresso Americano de Obstetras e Ginocologistas (ACOG).

E se você acha que viu um aumento nos nascimentos múltiplos nos Estados Unidos, você está certo. As mulheres estão engravidando mais tarde na vida e as mães na faixa dos 30 e 40 anos são mais propensas a conceber mais de um bebê. Aumentando as chances de dar à luz múltiplos? Tratamentos de fertilidade .

Você sabia?

Para ajudar a conter a onda de nascimentos múltiplos, a Sociedade Americana de Medicina Reprodutiva publicou recentemente diretrizes limitando o número de embriões que podem ser implantados durante a fertilização in vitro.

Mulheres que têm doenças crônicas como diabetes , defeitos cardíacos ou doenças renais tendem a ter gestações mais difíceis. Como resultado, eles são mais propensos a dar à luz prematuros e ter bebês com baixo peso ao nascer.

O Congresso Americano de Obstetras e Ginecologistas (ACOG) aconselha essas mulheres a trabalhar em estreita colaboração com seus médicos no gerenciamento de suas condições crônicas. Ajustes na dieta, medicamentos e níveis de atividade podem ajudar a evitar o risco de parto prematuro.

Complicações e doenças específicas da gravidez também podem levar ao parto prematuro. Por exemplo, se as bactérias infectarem o útero, o parto imediato é necessário.

Outra ameaça é a pré- eclâmpsia , com suas características de pressão alta e proteína na urina. Esta doença perigosa e pouco compreendida afeta mais comumente mães mais velhas, mães de primeira viagem e mães de múltiplos. A doença corta nutrientes para os bebês e pode causar convulsões mortais nas mães. O parto imediato é a única maneira segura de salvar a mãe e o bebê.

Além de pressão alta e proteína na urina, os sintomas de pré-eclâmpsia podem incluir inchaço nas mãos, rosto ou pés, dor de cabeça, visão turva e dor abdominal, de acordo com os Institutos Nacionais de Saúde.

Você sabia?

Preeclampsia and it's more full-blown form, eclampsia, affect 10 percent of pregnancies in the United States, costing $3 billion a year and causing 15 percent of premature births, according to Preeclampsia.org. Medical researchers still don't know what causes the disease.

It might not come as a surprise that a baby's health may be impacted if the mother smokes during pregnancy . But did you know that it doubles the risk of delivering a low birth weight baby and increases the risk of delivery of a preterm birth?

The main reason is that smoking delivers the harmful chemicals tar, nicotine , and carbon monoxide to the fetus. These substances reduce the baby's oxygen supply, slowing its growth and development. The more cigarettes a woman smokes, the more likely she is to have an underweight baby.

The good news: A mother can reduce her baby's risk of being born underweight by quitting smoking at any point in the pregnancy, according to the American Congress of Obstetricians and Gynecologists (ACOG).

Over the past several decades, the public has grown increasingly aware of the problems drugs and alcohol can cause in pregnancy . Research has linked alcohol, illicit drugs -- and even some over-the-counter medications -- to birth defects and slowed development in infants.

The American Congress of Obstetricians and Gynecologists (ACOG) advises pregnant women to avoid all medications and drugs as much as possible, but to check with their doctor before discontinuing any prescription medications.

Some of the biggest developmental offenders are marijuana, heroin, cocaine, Ecstasy and other amphetamines. Heavy use of these drugs is associated with low birth weight, preterm birth, congenital problems, and learning and developmental disabilities.

Alcohol is perhaps the most commonly abused substance in pregnancy. In moderate to large amounts it can cause fetal alcohol syndrome -- a condition that may involve reduced baby size or weight as well as learning and developmental problems -- and raise the risk of premature delivery .

The cervix, or opening to the uterus, serves as something of a lockbox in a pregnancy. When the fetus anchors itself in the womb, the cervix slams shut to secure the developing baby and keep out germs. But sometimes, in cases of cervical incompetence, the cervix fails to close properly. As the baby grows, it puts increasing pressure on the opening, possibly spurring premature labor and delivery.

Doctors typically manage cervical incompetence by putting a stitch in the cervix, known as a cerclage, to help keep the baby going through 37 to 38 weeks. In many cases, bed-rest is also advised.

Uterine fibroids and malformations of the uterus can also limit a baby's development. For example, a bicornuate uterus has two hornlike chambers instead of the usual oval shape. If the baby establishes in one of these smaller chambers, it has limited room to grow. In these cases, miscarriage or preterm delivery is often common, according to The American Academy of Family Physians (AAFP).

Did You Know?

Management of preterm labor and preterm birth account for health care expenditures of over $3 billion per year, according to the AAFP (Familydoctor.org).

The placenta is a nutrient-rich lifeline from mother to infant, so when it is compromised, the infant's growth can suffer.

Several types of placental problems can interfere with a baby's growth. One is placenta previa, in which the placenta fuses to the cervix, covering all or part of the opening. Even more common is placental abruption, in which the placenta starts separating from the uterine wall during the pregnancy, before delivery. Affecting about one percent of pregnancies, the condition can, in serious cases, reduce the flow of nutrients and oxygen to the baby.

Placental problems are often associated with preterm births and low birth weight.

To properly develop and thrive, infants need a steady, rich supply of nutrients from the mother. For example, folic acid helps establish the brain and spinal column, and proteins build the infant's exploding cells.

A healthy, varied diet -- high in fruits, vegetables, grains, nuts, lean meats and dairy -- is key to the development of a full-term, vigorous baby. On the other end of the spectrum, a diet restricted to foods low in nutritional value, like processed sweets, can slow fetal growth.

Not eating enough food during pregnancy can also limit a baby's growth. Recommended weight gain for a typical pregnancy is 25 to 35 pounds, according to the American Congress of Obstetricians and Gynecologists (ACOG).

Did You Know?

Doctors recommend that women take 400 micrograms of folic acid daily for at least a month before becoming pregnant, and during the first three months of pregnancy to help prevent defects of the spine and skull.

As much as pregnant women may act like heroes, some even working at the office every day right up to delivery, this is a sensitive time for them and their babies.

During pregnancy, women's bodies are pumping 40 to 50 percent more blood than usual -- their hearts working 30 to 50 percent harder -- and they can feel tired and uncomfortable, according to the Cleveland Clinic's Center for Continuing Education.

But the fact is, many pregnant women work for a living, some of them putting in long work hours and standing for extended periods of time. That toiling can put extra stress on a pregnancy, possibly interfering with fetal growth and full-term delivery. Other contributors to pregnancy stress are exposure to harmful chemicals (in factories for example, or while cleaning the house) or lack of emotional support from family and friends.

Some birth defects can impede normal development in the infant and lead to preterm birth. For example, if an infant develops problems like transposition of the heart's great arteries or spina bifida (open spine) -- a condition in which the neural tube fails to close properly -- doctors may need to perform surgery while the baby is still in the womb, which raises the risk of preterm birth.

A recent study in the journal Obstetrics & Gynecology found that the birth defects most commonly associated with preterm delivery include:

Did You Know?

Heart defects are the most common of all birth defects, affecting one in every 100 to 200 pregnancies. Defects of the palate and lip -- cleft lip and cleft palate -- are next, followed by defects of the spine and brain and Down syndrome, according to the U.S. Centers for Disease Control and Prevention (CDC).

For a pregnant mom, catching a common illness like a cold or the flu can raise concerns about harm to the baby. But these everyday illnesses don't typically threaten a developing infant.

There are, however, some less common viral and parasitic infections that can indeed cause fetal problems like slow growth, and even birth defects. According to the U.S. Centers for Disease Control and Prevention (CDC), here are a few to watch for:

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