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From Conception to Birth foetus obg fort
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- 2. INTRODUCTION An unborn OffspringThat develops and grows inside the Uterus (womb) Of humans and other mammals. In humans fetal Period begins from 8t h week after fertilization and it ends at the time of birth.
- 3. DEVELOPMENT OF FETUS Thefetus grows from a diploid zygote to almost 6 billion cells by 38 weeks of gestation and at the time of birth the baby weighting on an average of 2.9kg. This fetal growth is influenced by genetic factors, placental factors, sex of the fetus,parity and maternal nutrition. Fetal growth can be judged by maternal weight gain , symphyseofundal height and Ultrasound
- 5. Respiratory system Breathing movementare present as early as 11 weeks but these are irregular,become regular as term approaches.. Final stage of alveolar development occurs by 23 weeks Type 2 pneumocytes also produce surfactant,which prevent alveolar collapse.
- 6. Clinical importance ofsurfactant The presence of surfactant in amniotic fluid is evidences of fetal lug maturity. Surfactant is composed of 90% lipids and 10% protein 80% of the glycerophospholipids are phosphatidyl choline(lecithin). The main active component of surfactant is dipalmitoyl phosphatidyl choline. Second active component is phosphatidyl glycerol.these components along with phosphatidyl inositol are very important for the prevention of RDS.
- 7. Renal system Excretory functionis mainly carried out by placenta . In late pregnancy amniotic fluid sodium level fall while creatinine rises.this is because the fetal kidney is unable to conserve sodium efficiently. The kidney produce 500-700ml of urine per day and this is the major contributor to liquor volume from approximately 20 weeks.
- 8. Central Nervous system After3 weeks of post implementation the CNS begins to form. However , functional maturity is attained much later. Blood supply to the brain is always maintained and even in fetal growth restriction, there is brain sparing effect.
- 9. Peripheral Nervous system Gangliaand nerves appear by 28-35 days , however motor and sensory nerve endings appear later (12-16weeks) The autonomous nervous system with the baroreceptor mechanisms and pulmonary reflexes mature only towards term.
- 10. Skin Sabaceous glands areresponsible for the production of vernix caseosa Sweat glands do not function very early they are not required to regulate any water or eletrolyte balance ,as this is done by placenta .
- 11. Alimentary Tract The fetusswallows fluid as early as 12 weeks and at term, almost 250ml/day The villi and glands are formed early and digestive enzymes can be seen by 16-18 weeks . The first stool of the New born is called ‘Meconium’. It is dark in colour due to biliverdin. This meconium contains cell,hair,Mucous and other intestinal meterials.
- 12. Reproductive system T estis isformed by 8 weeks and the Ovary is formed by 10 weeks. The wolffian and Mullerian structures are formed by 10- 12 weeks. The external genitalia upto 10 weeks consisting of 2-urogenital fold,2-genital swelling and a midline anterior genital tubercle. In female genital tubercle – clitoris Genital fold - labia minora Genital swelling – labia majora The male development completed by 12 weeks ,and female development by 15 weeks.
- 13. Cryptorchidism It is acondition in males where one or both testicles fails to decent From the abdomen to scrotum. It can be identified by an empty scrotum at birth. Un treated cryptorchidism can lead to infertility and increase risk of Testicular cancer. Surgery – Orchiopexy .
- 14. HAEMATOLO GICAL CHANGES 1. HAEMOPOIESIS (BLOODCELL FORMATION) SITES OF HAEMOPOIESIS a)YO L K SAC •First RBCs formed at 14 days. •Produces macrocytic, nucleated RBCs with polychromatic cytoplasm •Not influenced by erythropoietin. b)LIV ER •Becomes haemopoietic from 6–10 weeks. •Major site in 1st & early 2nd trimester. •Activity declines in 2nd trimester; stops by term. c)B O N E M A R R OW • Starts forming blood cells at 7–18 weeks. • Progenitor cells present by 15–16 weeks. • Becomes dominant site by mid-gestation onwards. d)SPLEEN •Starts haemopoiesis at 19–20 weeks. e)T H Y M U S & LY M P H N O D E S •Act as supplemental sites during the 3rd trimester. 1. Haemopoiesis (Blood Cell Formation) 2. Red blood cells 3. Haemoglobin 4. Leucocytes and platelets 5. Immunoglobulins
- 15. 2. RED BLOOD CELLS ►RBC concentration increases throughout gestation. ► At term: 5.1 × 10¹² / L. ► Hemoglobin rises from 6 g/dL (10 weeks) to 16–18 g/dL at term. ► Packed cell volume increases from 20% → 40%. ► Fetal RBCs are larger and more numerous. ► Fetal RBC lifespan ≈ 80 days. ► The Rh factor is developed by 38 days.
- 16. 3. HAEMOGLOBIN HbF (α₂γ₂) 30%at 5 weeks. ≈90% of total Hb by 8 weeks. High oxygen affinity (→ efficient oxygen transfer from mother). It is resistant to alkali and acid. Oxygen affinity: 80% in fetus vs. 40% in mother. HbA (α₂β₂) ► Appears at 5–10% throughout gestation. ► Increases after 32–36 weeks. ► <1% after 4 months of birth. ► Fetal blood carries 25 mL O₂ / 100 mL blood(maternal blood carries 15 mL). ► Rh factor develops by 38 days.
- 17. 4. LEUKOCYTES AND PLATELETS ►Leukocytes increase progressively. At term: 15,000– 20,000 / mm³. Thymus & spleen → major lymphocyte sources. Fetus produces minimal antibodies (mostly maternal transfer). Platelet : •Megakaryocytes appear in yolk
- 18. 5.IMMUNOGL OBULINS • IgG →Only immunoglobulin thatcrosses the placenta. →Transfer begins at 12 weeks. →Provides passive maternal immunity. •IgM →Produced by fetus (does not cross placenta). →Presence at birth suggests intrauterine infection. •IgA →Produced only after birth
- 19. CARDIOVASCUL A R SYSTEM Developmentof the Heart 1.The heart appears as two tubes at 18 days of embryonic life. 2. These tubes fuse into a single heart tube by 22 days. 3. The heart tube elongates and forms chambers. 4.The heart starts beating by 22 days, but it is detected clinically much later.
- 20. Development of the heart Hea d Tail 18days Cardiogeni c area Primitive blood vessels Blood flow 20 days 23 days Endocardial tubes Truncus anerlosus Bulbus Ventricle Atrium venosus 21 days 24 days Fusion into primitive heap tube Right atriu m Ventricle Atrium venosus 22 days 35 days Truncus aFeriosus — Bulbus cordis atrium Aortic arch aFeries Truncus aFeriosus Leh atrium Ventricle
- 21. Right Ventrlcte Right Atrlum | )” Inferior vena cava Ouctus venosus Umbilical vein FetaL Circu£ation ForamenOvule j t” Liver Lungs PuImonary Veins Left Atriu m Placenta Left Ventricfe ! Duct us Aneriosus I Aorta ”” ””• I Systemic Circulation Umbilical Arteries
- 24. 1. Foramen ovalecloses 2. Ductus arteriosus closes – First breath → lungs expand → ↓ pulmonary artery pressure → duct constricts. – Becomes ligamentum arteriosum. – Prostaglandins keep it open; inhibitors help close it. 3. Umbilical arteries close – Proximal part: becomes superior vesical arteries – Distal part: forms lateral umbilical ligaments 4. Umbilical vein closes – Occurs shortly after arteries – Forms ligamentum teres 5. Ductus venosus closes – Forms ligamentum venosum - -- If you want, I can make it into a flowchart, table, or ultra-short 1-slide summary too. CHANGES AT BIRTH When the cord is clamped → veCnoIusRreCturnUto rLighAt atTriuOm dRropsY→ changes occur: – ↓ Right atrial pressure → flapSshuYts S(funTctioEnaMl at birth; anatomical later).
- 26. RESPIRATORY SYSTEM –CHANGES ATBIRTH Surfactant – Produced by Type II pneumocytes – Reduces surface tension → prevents alveolar collapse First breath triggers – Drop in skin temperature – Tactile stimulation – Hypoxia & hypercapnia after cord clamping – These activate brainstem respiratory centers Lung fluid removal – During birth, ↑ intrathoracic pressure squeezes out lung fluid Air entry into lungs – Chest expands → air enters alveoli → breathing cycle starts Adaptation to life outside womb – Baby becomes capable of independent extrauterine
- 28. CLINICAL CORRELATIO N Neural Tube Defects:Failure of closure → anencephaly, spina bifida ( ↓ folate, ↑ AFP). Cardiac Anomalies: Faulty septation → ASD, VSD, TOF picked on NT/ anomaly scan. GI Malformations: Abnormal midgut rotation → Omphalocele; imperforate anus. Renal Issues: Renal agenesis → oligohydramnios & Potter sequence; pelvic kidney. Respiratory Problems: Surfactant deficiency in preterm → RDS. Craniofacial Defects: Failed fusion → cleft lip/palate. Placental & Cord Abnormalities: Previa/accreta, single umbilical
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