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Placental Functions and Factors Affecting Fetal Growth

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Placental Functions and Factors Affecting Fetal Growth

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    1. Placental Functions and Factors Affecting Fetal Growth

    5. Maternal Placental Blood Flow Intervillous space of mature placenta contains about 150 ml of blood which is replenished 3 or 4 times a minute Uteroplacental blood flow increases from 50 ml per minute atr 10 weeks 500/600 ml per minute at full term

    6. Placenta Metabolism Transfer Endocrine

    7. Placental Transfer (gases) Oxygen, Carbon Dioxide, Carbon Monoxide cross the placenta by simple diffusion

    8. Placental Transfer (nutrients) Water freely moves No transfer of maternal cholesterol, triglycerides or phospholipids Small amounts of free fatty acids transported vitamins are essential Glucose quickly transferred

    9. Placental Transfer (hormones) Protein hormones do not reach the fetus, except for the slow transfer of thryroxine and triiodothyronine Testosterone can cross

    10. Placental Transfer (antibodies) Some passive immunity is conferred on the feus by the transfer of maternal antibodies (mainly gamma globulins) diptheria, smallpox and measles not whooping cough and chicken pox

    11. Glucose Glucose is the primary source of energy for the fetal metabolism Amino acids also required Both come from the mother via the placenta

    12. Placental Metabolism Particularly early in pregnancy, synthesis of glycogen, cholesterol and fatty acids

    13. Dizygotic Twins

    14. Dizygotic Twins

    15. Monozygotic Twins

    18. Critical Periods Since organogenesis occurs primarily in the embryonic period (weeks 4-8) slight influences can have drastic and irreversible effects Sensitive periods?

    20. Congenital Malformations Malformations present at birth, irrespective of cause (genetic or environmental)

    21. Teratogens External agents that cause congenital malformations Alcohol (Fetal alcohol Syndrome; FAS) Thalidomide Radiation (Power Lines?) Lithium Viruses (Rubella - German Measles)

    22. Thalidomide

    23. Rubella Syndrome Symptoms in the infant may include: Cloudy corneas or white appearance to pupil, Deafness, Developmental delay, Excessive sleepiness, Irritability, Low birth weight, Mental retardation, Seizures, Small head size, Skin rash at birth, Cardiac Anomalies

    24. Fetal Monitoring

    25. Ultrasonography Monitoring: Chorionic sac during embryonic period placental and fetal size multiple births abnormal presentations biparietal diameter

    26. Fetal Blood Sampling Usually from the scalp, fetal blood pH is a good indicator of placental gas exchange. In the past, fetal blood sampling was used only during labor through the mother's open cervix to test blood from the fetal scalp for oxygenation.

    27. Fetal Blood Sampling A fetal blood sample may be taken to: diagnose genetic or chromosome abnormalities. check for and treat severe fetal anemia or other blood problems such as Rh disease. check for fetal oxygen levels. check for fetal infection. give certain medications to the fetus.

    28. How is fetal blood sampling performed? A long, thin needle is inserted into the mother's uterus guided by ultrasound. Blood may be taken from several sources: blood vessels of the umbilical cord (also called cordocentesis, funicentesis, or percutaneous umbilical blood sampling, or PUBS) a fetal blood vessel, usually in the liver or heart Fetal blood transfusions may also be performed in this

    29. used in prenatal diagnosis of chromosomal abnormalities and fetal infections, in which a small amount of amniotic fluid, which contains fetal tissues, is extracted from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for genetic abnormalities. Little amniotic fluid present prior to 12th week of gestation

    30. Chorionic Villus Sampling chromosomal abnormalities etc. The advantage of CVS is that it can be carried out 10-13 weeks after the last period, earlier than amniocentesis (which is carried out at 16-20 weeks).

    31. Alpha-Fetoprotein Assay AFP is a glycoprotein synthesized in the fetal liver and yolk sac. The fetus normally excretes AFP into its urine, hence into the amniotic fluid. High levels may also be present due to: open neural tube defect open abdominal wall defect skin disease or other failure of the interior or exterior body surface. Various forms of tumours

    32. Factors Affecting Fetal Growth

    33. Placental Insufficiency Placental defects effectively reduce available surface area reduced uteroplacental blood flow may also occur due to maternal hypotension or renal disease.

    34. Multiple Pregnancy Individuals of multiple births usually weigh considerably less in the third trimester placenta may not be able to supply the total requirements for multiple births

    36. Small Babies Low birth weight: < 2,500g Premature: < 37 weeks of gestation Small for Date: Smaller than expected for age

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