Birth weight

Birth weight is the body weight of a baby at its birth. The average birth weight in babies of European heritage is 3.5 kilograms (7.7 lb), though the range of normal is between 2.5 kilograms (5.5 lb) and 4.5 kilograms (9.9 lb). Babies of south Asian and Chinese heritage weigh about 240 grams (0.53 lb) less. The birth weight of a baby is notable because very low birth weight babies are 100 times more likely to die compared to normal birth weight babies. As far as low birth weights prevalence rates changing over time, there has been a slight decrease from 7.9% (1970) to 6.8% (1980), then a slight increase to 8.3% (2006), to current levels of 8.2% (2016). The prevalence of low birth weight has trended slightly upward from 2012 to present day. Birth weight is the body weight of a baby at its birth. The average birth weight in babies of European heritage is 3.5 kilograms (7.7 lb), though the range of normal is between 2.5 kilograms (5.5 lb) and 4.5 kilograms (9.9 lb). Babies of south Asian and Chinese heritage weigh about 240 grams (0.53 lb) less. The birth weight of a baby is notable because very low birth weight babies are 100 times more likely to die compared to normal birth weight babies. As far as low birth weights prevalence rates changing over time, there has been a slight decrease from 7.9% (1970) to 6.8% (1980), then a slight increase to 8.3% (2006), to current levels of 8.2% (2016). The prevalence of low birth weight has trended slightly upward from 2012 to present day. There have been numerous studies that have attempted, with varying degrees of success, to show links between birth weight and later-life conditions, including diabetes, obesity, tobacco smoking, and intelligence. Low birth weight is associated with neonatal infection and infant mortality. There are two genetic loci that have been strongly linked to birth weight, ADCY5 and CCNL1, as well four that show some evidence (CDKAL1, HHEX-IDE, GCK, and TCF7L2). The heritability of birth weight ranges from 25-40 %. There is a complex relationship between a baby's genes and the maternal environment that the child is developing in. Foetal genes influence how the fetus grows in utero, and the maternal genes influence how the environment affects the growing fetus. The health of the mother during the pregnancy can affect birth weight. Intercurrent diseases in pregnancy are sometimes associated with decreased birth weight. For example, celiac disease confers an odds ratio of low birth weight of approximately 1.8. Certain medications (e.g. for high blood pressure or epilepsy) can put a mother at a higher risk for delivering a low birth weight baby.Giving birth to a child when you are younger than 15 or older than 35 puts you at a higher risk to have a low-birth weight baby. Multiple births, where a mother has more than one child at one time, can also be a determinant in birth weight as each baby is likely to be outside the AGA (appropriate for gestational age). Multiple births put children at a higher rate to have low birth weight (56.6%) compared to children born in a single birth ( 6.2%). Low birth weight can also vary by maternal age. In 2008 the rate of low birth weight was the highest in babies born to women younger than 15 years old (12.4%). Women aged 40–54 had a rate of low birth weight at 11.8 percent. The lowest rates of low birth weight happened among babies whose mothers were between the ages of 25–29 years (4.4%) and 30–34 years (7.6%). Stressful events have been demonstrated to produce significant effects on birth weight. Those mothers who have stressful events during pregnancy, especially during the first and second trimester, are at higher risk to deliver low-birth weight babies. Researchers furthered this study and found that maternal stressful events that occur prior to conception have a negative impact on birth weight as well, and can result in a higher risk for preterm and lower birth weight babies. Women who experienced abuse (physical, sexual, or emotional) during pregnancy are also at increased risk of delivering a low-birth weight baby. For example, in a study completed by Witt et. al, those women who experienced a stressful event (ie. death of close family member, infertility issues, separation from partner) prior to conception had 38% more of a chance to have a very low birth weight baby compared to those who had not experienced a stressful life event. The theory is that stress can impact a baby based on two different mechanisms: neuroendocrine pathway or immune/inflammatory pathway. Stress causes the body to produce stress hormones called glucocorticoids that can suppress the immune system., as well as raises levels of placental corticotropin-releasing hormone (CRH) which can lead to preterm labor. These findings can pose evidence for future prevention efforts for low birth weight babies. One way to decrease rates of low birth weight and premature delivery is to focus on the health of women prior to conception through reproductive education, screening and counseling regarding mental health issues and stress, and access to primary care. Non-Hispanic Blacks have the highest infant mortality rate in the United States (11.4 deaths per 1,000 live births compared to the national average of 5.9 deaths per 1,000 live births). Subsequently, there has been growing research supporting the idea of racial discrimination as a risk factor for low birth weight. In one study by Collins et. al, evidence suggested that African American mothers who experienced high levels of racial discrimination were at significantly higher risk of delivering a very low-birth weight baby compared to African American mothers who had not experienced racial discrimination. Black infants (13.2%) are more likely to have low birth weight compared to Asian and Pacific Islander (8.1%), American Indian and Alaska Native (7.6%), Non-Hispanic White (7.0%), and Hispanic Infants (7.1%). Environmental factors, including exposure of the mother to secondhand smoke can be a factor in determining the birth weight of child. In 2014, 13% of children exposed to smoke were born with low birth weight compared with 7.5% of those children born to nonsmokers. Children born to mothers who smoked or were exposed to secondhand smoke are more likely to develop health problems earlier in life such as neurodevelopmental delays. When mothers actively smoke during pregnancy, their child is at a higher risk of being born with a low birth weight. Smoking can also be a stress management tool used by expecting mothers. There is some support for lower socioeconomic status of the parents being a determinant of low birth weight, but there is conflicting evidence, as socioeconomic status is tied to many other factors. Most babies admitted to the NICU are born before 37 weeks of pregnancy or have low birth weight which is less than 5.5 pounds. They could also have a medical condition that requires special care. In the United States nearly half a million babies are born preterm because of this many of these babies also have low birth weights. There are four levels of care in the neonatal care units. Intensive Care, High Dependency Care, Low Dependency, and Transitional Care are the four levels: Children born with an abnormally low birth weight can have significant problems within the first few years of life. They may have trouble gaining weight, obtaining adequate nutrition, and supporting a strong immune system. They also have higher risks for mortality, behavior problems, and mental deficiencies. Low birth weight babies are more likely to develop the following conditions after birth compared to normal birth weight babies: