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%). Stress
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 (i.e. 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.
Birth weight is the body weight of a baby at its birth. The average birth weight in babies of European descent is 3.5 kilograms (7.7 lb), with the normative range between 2.5 and 4.5 kilograms (5.5 and 9.9 lb). On average, babies of South Asian and Chinese descent weigh about 3.26 kilograms (7.2 lb). As far as low birth weight 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 the current levels of 8.2% (2016). The prevalence of low birth weights has trended slightly upward from 2012 to the present.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. Abnormalities
A low birth weight can be caused either by a preterm birth (low gestational age at birth) or of the infant being small for gestational age (slow prenatal growth rate), or a combination of both. Potential causes of low birth weight can also be cause by health issues in the person giving birth, genetic factors, or problems in the placenta. A very large birth weight is usually caused by the infant having been large for gestational age. Infants that are large for gestational age have been associated with significantly higher rates of neonatal morbidity.