Adjustments to Extrauterine Life By : Mohammad Abuadas RN, MSN

What after birth??? The most important physiologic change required of the neonate is the transition from fetal or placental circulation to independent respiration out of the uterus. “Fetal Asphyxia” is considered to be the most fatal abnormal stressor after labor.

Immediate adjustments after birth Respiratory system: Chemical factors in the blood (low pH, high CO2), which stimulate the presence of impulses that excite the respiratory center in the medulla. The production of the “surfactant” by the alveoli epithelium that facilitate breathing.

The circulatory system: The changes in the circulatory system occurs gradually due to the pressure in the lungs, heart and vessels. The closure of the fetal shunts which are : foramen ovale, ducus arteriosus, and the ductus venosus.

Thermoregulation : “”HEAT LOSS”” is the most critical event in the thermoregulation process, the factors behind that heat loss are : 1- the newborn’s large surface area facilitates heat loss to the environment by Convection, conduction, radiation, and evaporation.

Thermoregulation 2- the newborn’s thin layer of subcutaneous fat provides poor insulation for conservation of heat. 3- the newborn’s nonshivering thermogenesis. “” brown adipose tissue or brown fat, from mitochondria is the main heat producer in the newborn infant.

The hemopoietic system The fetal blood volume depends on the amount of blood transferred from placenta. The blood of the full term infant is about 80 to 85 ml/kg of body weight. After birth, the blood volume averages 300 cc. added to 100 from placental circulation.

Fluid and electrolyte balance At birth, the total weight of the infant is 73% fluids, as compared with 58% in the adult. The infant rate of metabolism is twice greater than that in adults, leading to acidosis.

Gastrointestinal system Digestion of only monosaccharide (simple carbohydrates ) in the early stages. The immature liver causes conjugation of billirubin, causes physiologic jaundice. Salivary gland don’t function till 2 to 3 months of age, when drooling become frequent. Infant’s stomach capacity is about 90cc. Infant’s intestine is longer than adult’s in relation to their sizes.

Integumentary system At birth, all skin structures are present but found immature. The “sebaceous glands” are very active late in fetal life and early infancy related to the androgens, they are present in the face, scalp, and genitalia producing greasy “vernix caseosa” that covers the infant at birth. The eccrine (sweat) glands are functiong. The apocrine gland remain immature till puberty. The newborn colors are lighter at birth because melanin is low at birth.