User:ElizabethHu3/First 1000 days

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The first 1000 days describes the period from conception to 24 months of age in child development. This is considered a "critical period" in which sufficient nutrition and environmental factors have life-long effects on a child's overall health. While adequate nutrition can be exceptionally beneficial during this critical period, inadequate nutrition may also be detrimental to the child. Medical and public health interventions early on in child development during the first 1000 days may have higher rates of success compared to those achieved outside of this period.

Adequate Nutrition during the first 1000 days can have a direct and indirect influence on both short and long term health outcomes. Sufficient overall nutrition within the first 1000 days is vital to healthy neurological and physical growth. This includes adequate amounts of macronutrients, micronutrients, as well as essential vitamins. The concept of adequate nutrition applies to both the carrying mother as well as the child. Key macronutrients include proteins and long-chain polyunsaturated fatty acids (LC-PUFA), while some key micronutrients include Iron, zinc, Iodine, calcium, and magnesium. Essential vitamins are also vital. This includes: Vitamin A:  which is key for fetal development, organogenesis, limb formation,  immune functions, mucosal integrity and body symmetry. A lack of vitamin A can lead to xerophthalmia, night blindness, and anemia. Vitamin D:  which is essential for bone development. While a deficiency can lead to the development of rickets disease. Folate/folic acid: which prevents neural tube defects (NTDs). Children who do not receive adequate nutrition in the first 1000 days can suffer short and long term health consequences. Some of these consequences can be mitigated if identified and addressed early however they may become harder to rectify as more time passes. There are various risk factors in the first 1000 days which, if present, are predictors of later obesity.

Children establish many of their lifetime epigenetic characteristics in their first 1000 days, impacted by maternal nutrition and environmental stressors.

Stunted growth may be remedied (catch-up growth) by attainment of proper nutritional status. This is especially important in adolescent girls, where it may break a cycle of inter-generational underdevelopment.

Interventions
Advancements in medical intervention technologies have allowed for significant improvements in perinatal and neonatal mortality and morbidity. For example, cochlear implants have improved treatment of congenital deafness.

Microbiota
The first 1000 days of the human microbiome starting from time of conception until 2 years old is a critical time period for growth and development, including nutrients and microbiota. During this time frame of early childhood growth, there are many immune and developmental pathways that are dependent on environmental factors such as nutrients; malnutrition can disrupt growth and development leading to obesity or malnutrition.

During pregnancy, the key microbiota are maternal microbiota and fetal microbiota. Microbiota from the mother is essential for the child's growth even before birth. Pre-birth microbial exposure, either excessive or lack of, can impact growth and development negatively and have long-term effect.

The first 6 months after birth is characterized by external exposure to microbiota. For instance, different feeding practices leads to different outcomes; breastfeeding and commercial milk will have different essential nutrients and micriobiota. Antibiotics may have an affect on the gut microbiota.

Transitioning into childhood, food intake after 6 months will be changed from milk to complementary foods; this is a critical period for children to get adequate nutrition necessary for growth. From this period, environmental factors start to impact the children more. In underserved communities where families may face food insecurities or poor living conditions, the risk of undernutrition and negative affect to microbial pathway may increase. Cases of undernutrition may be treated by gut microbiota targeted interventions in combination with nutrition; this will restore the lack/loss of microbiota the child has faced during their childhood and promote healthy growth.

Breastfeeding and vaginal birth forms the infant's microbiota which can protect against allergies from developing.

Epigenetics
Epigenetic programming is highly impacted in development and early childhood, and plays a role in

Nutrition
Both maternal and early-childhood nutrition influence epigenetic changes, which then inform immunologic and metabolic outcomes throughout development and into later life. Present in human milk are HMOs, bioactive components which aid in immune function and regulation, and miRNA-containing exosomes. HMOs can be fermented into short-chain fatty acids, which play important roles in modulating the microbiome and in T cell differentiation, and may positively correlate with methylation levels. miRNA found in milk-derived exosomes may increase immune tolerance.

Metabolic disease, and particularly type 2 diabetes mellitus and insulin resistance, is strongly associated with malnutrition. Both parental undernutrition and overnutrition predispose a child to developing these conditions. Under these circumstances, differential methylation of adipose tissue genes and miRNA upregulation in adipose tissue and the pancreas may occur.

Stress Exposure
Exposure to emotional, physical, and environmental stressors significantly affect the developing brain, which may later manifest in negative mental- and health-related outcomes through the HPA axis' role in stress regulation.

Maternal depression, anxiety, and stress may be associated with increased rates of mental disorders, including schizophrenia, depression, anxiety, ADHD, and autism in the child. Smoking in pregnancy is associated with differential methylation of genes implicated in brain development, central nervous system disorders, asthma, and various cancers. Stress management and smoking cessation in the birthing parent provide avenues for reducing this risk.

Babies born prematurely are often separated from the birthing parent and sequestered in neonatal intensive care units, where they may require additional care and procedures. Stress caused to the infant during this process is associated with epigenetic modifications relating to behavioral issues and stress regulation, notably hypermethylation of the SLC6A4 gene.

Other forms of childhood adversity, which include abuse or neglect, similarly impact a child's development through differential epigenetic programming and stress response dysregulation. In addition to adverse effects on mental health, children who experience these events often exhibit dampened immune responses.

Criticism
The effectiveness of critical period hypothesis intervention in educational and social policy was questioned in The Myth of the First Three Years, noting the brain's capacity for later development, life-long learning, and advocating evidence-based research.