1. Fetal and Neonatal Physiology

2. Fetal & Neonatal physiology Goals  Fetal development  Functioning of the child immediately after birth  Growth and development through the early year of life  Fetal growth and functional development of organs system

3. Growth and Functional Development of Fetus At 12 weeks, fetus is about 10 cm long At 20 weeks, 25 cm At term, about 50 cm

4. Relative Size of Human Conceptus

5. Relative Uterus Size During Pregnancy

6. Function of the Placenta

7. Development of the Organ Systems Within 1 month, gross characteristics of all the organs have begun to develop During the next 2 -3 months, details of the organs are established Beyond 4 months, organs of the fetus are grossly the same as those of the neonate However, cellular development in each organ is far from complete

8. Development of the Organ Systems Circulatory system Beating of the heart begins (4tth week) Contracting of the heart- 65 beats/min Increases to 140 beats/min before birth Formation of Blood Cells 3 rd week-nucleated RBCs In york sac & mesothelial layers of the placenta 4 th to 5 th week- nucleated RBCs fetal mesenchymal & endothelium of fetal blood vessels 6 th week-RBCs-liver 3 rd month-spleen & other lymphoid tissue

9. Development of the Organ Systems  3 rd month onwards Principle source RBCs & most of WBC - bone marrow Lymphocytes & plasma cells- lymphoid tissue Respiratory System No respiratory activity during fetal life No air to breath in amniotic fluid Lungs are completely deflated Inhibition ! Prevents filling of the lungs with fluids and debris from meconium excreted by fetus’s git into the amniotic fluid

10. Development of the Organ Systems Nervous system 3 rd to 4 th month Spinal cord and brain stem reflexes are present Cerebral cortex is immature Myelinization of major tracts completed 1 yr of postnatal life Gastrointestinal by midpregnancy Fetus ingests and absorbs large quantities of amniotic fluid Last 2-3 months - function approaches that of normal neonate Formation of meconium during the last 2-3 months

11. Development of the Organ Systems Kidneys 2 nd trimester- urine excretion Accounts 70-80 % of amniotic fluid Oligohydramnios Reduced formation of amniotic fluids  Abnormal kidney development  Severe impairment of kidney function Renal control systems regulation of fetal e.c.f volume & electrolyte balances, esp acid base balance are almost non-existent until late fetal life Do not reach full development until a few months after birth

12. Development of the Organ Systems Fetal Metabolism Glucose is the sole source of energy Special problems about Ca, PO4, Fe and Vit metabolism Metabolism of Calcium and Phosphate 12 th -40 th accumulates Period of rapid ossification of fetal bones Weight gain of the fetus Accumulation of iron 3 rd weeks onwards Stored in the form of Hb Used for RBCs formation Most stored in the liver

13. Development of the Organ Systems  Vitamin utilization and storage  B vitamins (B12 & folic acid)  Formation of RBC & nervous tissues  Overall growth of fetus  Vit C  Intracellular substrate formation  Bone matrix  Fibers of connective tissue  Vitamins D  Is needed for normal bone growth  Is stored in the liver

14. Development of the Organ Systems Vit E Normal development of embryo Its absence Early stage abortion in animal studies Vit K Formation of Factor VII, prothrombin, other blood coagulation factors

15. Development of the Organ Systems

16. Adjustments of the Infant to Extrauterine Life onset of breathing Birth creates  Loss of placental connection  Loss of means of metabolic support Adjustment: beginning of breathing Cause of breathing at birth Breathing begins within seconds (less than a min) Sudden exposure to the exterior world Slightly asphyxiated state incident to birth process Sensory impulses – sudden cooled skin Additional stimuli-hypoxia & hypercapnia which stimulates respiratory centre

17. Adjustments of the Infant to Extrauterine Life Delayed or abnormal breathing at birth (danger of hypoxia) Hypoxia frequently occurs because of Compression of the umbilical cord Premature separation of placenta Excessive contraction of the uterus Excessive anaesthesia of the mother Degree of hypoxia that an infant can tolerate Failure to breath 4m-death in adults >8-10 permanent/serious brain impairment including death in neonates Damage-thalamus, inferior colliculi, brain stem Areas associated with motor functions of the body

18. Expansion of the Lungs at Birth At birth –Alveoli walls are collapsed due to surface tension of the viscid fluid that fills them >25mmHg –ve inspiratory pressure –opposes surface tension –opens them Fortunately –Ist inspiratory pressure 60mmHg –ve intrapleural pressure

19. Respiratory Distress Syndrome Deficient surfactant secretion Respiratory epithelium type 2 alveolar epithelia cells Respiratory distress syndrome Hyaline membrane disease Production of surfactant begins at 23 – 24 wks of gestation and reaches maturation after 35 wks of gestation Decreased surfactant production in preterm babies decreases the compliance risk for respiratory distress syndrome bronchopulmonary dysplasia and pulmonary hypertension

20. Circulatory Readjustments at Birth

23. Changes in the Fetal Circulation at Birth Primary changes in pulmonary and systemic vascular resistances at birth Hypoxia causes tonic constrictions in lung blood vessels in fetal life Pulmonary arterial pressure, right ventricular pressure and right atrial pressure are all reduced Closure of the foramen ovale 2 to 4 mm Hg pressure in the left atrium

24. Changes in the Fetal Circulation at Birth Closure of ductus arteriosus Failure of closure, role of prostaglandins Indomethacin, blocking the synthesis of prostaglandins Closure of ductus venosus Nutrition of the neonate Plasma glucose levels: 30-40 mg/dL Infant’s body fluid turnover is 7 times that of an adult

25. Special Functional Problems in the Neonate Instability of various hormonal and neurogenic control systems Respiratory system (40 times/min) Tidal volume: 16 ml Functional residual capacity is one half that of adult Excessive cyclical variations

26. Special Functional Problems in the Neonate Circulation, Blood volume: 300 ml Cardiac output: 500 ml/min Arterial pressure: at the first day, 70 / 50 mmHg Several months after birth: 90/60 mm Hg Blood characteristics: 4 million RBC/mm3 Neonate jaundice and erythroblastosis fetalis

27. Special Functional Problems in the Neonate

28. Fluid balance, acid-base balance and renal function Liver function Digestion, absorption and metabolism of energy foods and nutrition Secretion of pancreatic amylase is deficient Less fat absorption in the GI tract Low and unstable glucose concentration Synthesizing and storing new proteins

29. Special Functional Problems in the Neonate: Body Temperature

30. Special Functional Problems in the Neonate Metabolic rate and body temperature The normal metabolic rate of the neonate in relation to body weight is about twice that of the adult Nutritional needs during the early weeks of life Need for calcium and Vit D Necessity for iron in the diet Vit C deficiencey in infants Orange or similar juice supplementation during infancy Immunity & allergy

31. Endocrine Problems in the Neonate Normally, the endocrine system of the infant is highly developed at birth Mother receiving androgenic hormone and masculinisation of the female newborn Sex hormones from placenta and through milk Untreated diabetic mother – low plasma glucose concentrations Type II Diabetes mellitus (stimulation of fetal growth and increased birth weight) Type I Diabetes mellitus – high mortality rate

32. Endocrine Problems in the Neonate Hypofunctional adrenal cortex – agenesis of the adrenal gland Hyperthyroidism in the mother Hypothyroidism in the mother – cretin dwarfism

33. Special Problems of Prematurity Instability of the homeostatic control systems in the premature infant Instability of acid-base balance Low blood protein because of immature liver development & hypoproteinemic edema Inability of the infant to regulate calcium levels Variability of blood glucose levels Instability of body temperature Temperature tends to approach the surroundings

34. Special Problems of Prematurity Danger of Blindness Caused by Excess Oxygen Therapy in the Premature Infant Respiratory distress and hypoxia Excessive oxygen therapy in treating premature infants may lead to blindness Too much oxygen stops the growth of new blood vessels in the retina Growth of great mass of vessels Retrolental fibroplasia Breathing air with 40% O2 would be physiologic

35. Growth & Development of the Child