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FETAL DEVELOPMENT

FETAL DEVELOPMENT. Peggy Pannell RN, MSN. Learning Goals. Normal Fetal Development From ovulation to birth Teratogen Definition and potential effects on development. Blastocyst Conception Ductus arteriosus Embryo Fertilization Fetus Foramen Ovale HCG Implantation. L/S ration

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FETAL DEVELOPMENT

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  1. FETAL DEVELOPMENT Peggy Pannell RN, MSN

  2. Learning Goals • Normal Fetal Development • From ovulation to birth • Teratogen • Definition and potential effects on development

  3. Blastocyst Conception Ductus arteriosus Embryo Fertilization Fetus Foramen Ovale HCG Implantation L/S ration Gestational age Vernix Zygote Placenta Quickening Surfactant Teratogens Umbilical Cord Vocabulary

  4. FERTILIZATION • Begins with 46 pair of chromosomes, splits off to 23 then combine for a unique new 46 pair.

  5. Ovum Zygote Morula Blastocyst Embryo Fetus (Oh, Zee my baby eats fast) Stages and Time Frames

  6. First weeks of human development: Blastocyst embedded in endometrium. IMPLANTATION

  7. Ectoderm Mesoderm Endoderm PRIMARY GERM LAYERS

  8. GESTATIONAL AGE • Gestational age=Time since last menstrual period (LMP) • EDC, EDD, EDB • 266 Days after fertilization • 280 Days after onset of LMP Fertilization LMP Days 266 280 Weeks 38 40 Calendar Months 8 3/4 9 Lunar Months 9 1/2 10

  9. GESTATIONAL AGE Nagele’s Rule • Add 7 days to the first day of the last normal menstrual period, subtract 3 months and add 1 year. • Example: • 1st day of LNMP=December 16 2006 • add 7 days = Dec. 23 2006 • subtract 3 months = Sept 23 2006 • add 1 year =Sept 23 2007, estimated due date (EDD)

  10. TRIMESTERS Trimester 1st = week’s 1-13 2nd = week’s 14 - 26 3rd = week’s 27 and on (38-40 WEEKS)

  11. STAGES OF DEVELOPMENT

  12. Amnion Chorion Decidua basalis Decidua basalis Developing placenta Developing placenta Yolk sac Yolk sac Amniotic cavity Amniotic cavity Decidua capsularis Decidua capsularis Intrauterine cavity Intrauterine cavity Decidua vera Decidua vera Mucus plug(operculum) Mucus plug(operculum) Mucus plug(operculum) Mucus plug(operculum) Lacunae in decidua basalis filled with maternal blood Villi of fetal portion of placenta filled with fetal blood Umbilical cord (funis) Umbilical cord (funis) Intrauterine cavity Membranes: Membranes: Decidua capsularis Amnion (blends with umbilical cord) Amnion (blends with umbilical cord) Decidua vera Chorion (blends with placenta) Chorion (blends with placenta) FETAL MEMBRANES

  13. First TrimesterAt the end of four weeks: Baby is 1/4 inch in length Heart, digestive system, backbone and spinal cord begin to form Placenta (sometimes called "afterbirth") begins to develop The single fertilized egg is now 10,000 times larger than size at conception 1 Month

  14. First TrimesterAt the end of 8 weeks: Baby is 1-1/8 inches long Heart is functioning Eyes, nose, lips, tongue, ears and teeth are forming Penis begins to appear in boys Baby is moving, although the mother can not yet feel movement Month 2

  15. First TrimesterAt the end of 12 weeks: Baby is 2 1/2 to 3 inches long Weight is about 1/2 to 1 ounce Baby develops recognizable form. Nails start to develop and earlobes are formed Arms, hands, fingers, legs, feet and toes are fully formed Eyes are almost fully developed Baby has developed most of his/her organs and tissues Baby's heart rate can be heard at 10 weeks with a special instrument called a Doppler Month 3

  16. Second TrimesterAt the end of 4 months: Baby is 6 1/2 to 7 inches long Weight is about 6 to 7 ounces Baby is developing reflexes, such as sucking and swallowing and may begin sucking his/her thumb Tooth buds are developing Sweat glands are forming on palms and soles Fingers and toes are well defined Sex is identifiable Skin is bright pink, transparent and covered with soft, downy hair Although recognizably human in appearance, the baby would not be able to survive outside the mother's body Month 4

  17. Second TrimesterAt the end of 5 months: Baby is 8 to 10 inches long Weight is about 1 pound Hair begins to grow on baby's head Soft woolly hair called lanugo will cover its body. Some may remain until a week after birth, when it is shed. Mother begins to feel fetal movement Internal organs are maturing Eyebrows, eyelids and eyelashes appear Month 5

  18. Second TrimesterAt the end of 6 months: Baby is 11 to 14 inches long Weight is about 1 3/4 to 2 pounds Eyelids begin to part and eyes open sometimes for short periods of time Skin is covered with protective coating called vernix Baby is able to hiccup Month 6

  19. Third TrimesterAt the end of 7 months: Baby is 14 to 16 inches long Weight is about 2 1/2 to 3 1/2 pounds Taste buds have developed Fat layers are forming Organs are maturing Skin is still wrinkled and red If born at this time, baby will be considered a premature baby and require special care Month 7

  20. Third TrimesterAt the end of 8 months: Baby is 16 1/2 to 18 inches long Weight is about 4 to 6 pounds Overall growth is rapid this month Tremendous brain growth occurs at this time Most body organs are now developed with the exception of the lungs Movements or "kicks" are strong enough to be visible from the outside Kidneys are mature Skin is less wrinkled Fingernails now extend beyond fingertips Month 8

  21. Third TrimesterAt the end of 9 months: Baby is 19 to 20 inches long Weight is about 7 to 7 1/2 pounds The lungs are mature Baby is now fully developed and can survive outside the mother's body Skin is pink and smooth Baby settles down lower in the abdomen in preparation for birth and may seem less active Month 9

  22. AMNIOTIC FLUID • Clear, yellowish fluid surrounding the developing fetus. • Average amount 1000 ml. • Having < 300ml – Oligohydramnios, associated with fetal renal abnormalities. • Having > 2 L – Hydramnios, associated with GI and other malformations.

  23. AMNIOTIC FLUID • Protects Fetus • Controls Temperature • Supports Symmetrical Growth • Prevents Adherence to amnion • Allows Movement • Source of oral fluid • Acts as a excretion-collection repository

  24. UMBILICAL CORD Connecting link between fetus and placenta. • Transports oxygen and nutrients to fetus from the placenta and returns waste products from the fetus to the placenta. • Contains: 2 arteries and 1 vein supported by mucoid material (wharton’s jelly) to prevent kinking and knotting. • Contains NO pain receptors.

  25. PLACENTA

  26. Schematic drawing of placenta: how it supplies oxygen and nutrition to embryo and removes waste products. Deoxygenated blood leaves fetus through the umbilical arteries and enters placenta, where it is oxygenated. Oxygenated blood leaves placenta through the umbilical vein, which enters the fetus via the umbilical cord PLACENTA mom MOM Baby Baby

  27. PLACENTA Produce protein hormones: • Human chorionic gonadotrophin (HCG)- 8-10 days past conception, is basis for pregnancy test • Progesterone • Estrogen • Human Placental Lactogen

  28. PLACENTA • Sieve/filter – allows smaller particles through and holds back larger molecules. Passage of materials in either direction is effected by: • Diffusion: gases, water, electrolytes • Facilitated transfer: glucose, amino acids, minerals. • Pinocytosis: movement of minute particle

  29. PLACENTA • Mother transmits immunoglobulin G (IgG) to fetus providing limited passive immunity. • Leakage: caused by membrane defect: may allow maternal and fetal blood mixing.

  30. Capability of fetus to survive outside uterus at the earliest gestational age - 22-24 weeks Survival depends on: Maturity of fetal central nervous system Maturity of lungs VIABILITY

  31. RESPIRATORY SYSTEM • Terminal SAC period - 24 Weeks to birth • Growth of primitive alveoli • Pulmonary surfactants produced which act as wetting agents that prevent alveolar walls from sticking • Insufficient surfactant - RDS • Lecithin/Sphingomyelin-Phospho Lipids L/S Ratio 30-32 Weeks 1.2 : 1 35 Weeks 2:1 (MATURITY)

  32. CARDIOVASCULAR SYSTEM • 1st System to function • FHR 120-160/Min • Can hear FHR with doppler at 10-12 Weeks

  33. FETAL CIRCULATION • Arteries in umbilical cord and fetal body carry deoxygenated blood. • Vein in cord and those in fetal body carry oxygenated blood • Ductus venosus connects umbilical vein and inferior vena cava; bypassing portal circulation.

  34. FETAL CIRCULATION • Foramen Ovale allows blood to flow from right to left atrium, bypassing lungs. • Ductus Arteriosus allows blood flow from pulmonary artery to aorta, bypassing fetal lungs;

  35. HEPATIC SYSTEM • Liver functions 4-6 weeks • Full liver function after delivery • MUSCULO-SKELETAL SYSTEM • Bones and muscles develop by 4th week • Fontanels – areas where >2 bones meet • 7-8 Weeks arms & leg movements

  36. GASTROINTESTINAL SYSTEM • Forms during 4th week • Middle portion of the intestine projects out into cord during 5th week. Returns during 10th week. If this does not occur- Omphalocele present at birth • Meconium – Dark green to black tarry waste accumulated in the fetal intestine near term

  37. RENAL SYSTEM • Kidneys form in 5th week and begin to function 4 weeks later. • Voiding into amniotic fluid • Low volume can show renal dysfunction • Renal malformation can be diagnosed in utero. • GFR is low at birth

  38. NEUROLOGICAL SYSTEM • Formed from the ectoderm during the 3rd week • Respiratory effort 18 1/2 WKS • Swallowing 12 1/2 WKS • Sucking 29 WKS • Fetal movement felt 16-20 WKS (Quickening)

  39. ENDOCRINE SYSTEM • Thyroid gland 1st to develop • Insulin produced at 20 weeks INTEGUMENTARY SYSTEM • 7th week – Two layers of cells • Vernix caseosa –Protects skin • Lanugo – Fine hair • 10th week – Fingernails, toenails

  40. IMMUNE SYSTEM • Passive immunity - FROM MOM • Active immunity - FROM FETUS

  41. TWINS MULTIFETAL PREGNANCIES MULTIFETAL PREGNANCY

  42. Teratogens • Environmental exposures that can adversely effect the developing fetus • Maternal Conditions • Alcoholism, Diabetes, Endocrinopathies, Phenylketonuria (PKU), Smoking, Nutritional problems • Infections Agents • Rubella, Toxoplasmosis, Syphillis, Herpes Simplex, Cytomegalic Inclusion Disease, Varicella, Venezuelan Equine Encephalitis • Mechanical Problems (deformations) • Amniotic band constrictions, Umbilical Cord constraint, Disparity in uterine size and uterine contents • Chemicals, drugs, radiation, hyperthermia

  43. STAGES OF DEVELOPMENT

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