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 at 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

15. Monozygotic Twins

17. Conjoined 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

22. The Six Principles of Teratology Wilson 1959 1. Susceptibility to teratogenesis depends on the genotype of the conceptus and the manner in which this interacts with adverse environmental factors. 2. Susceptibility to teratogenesis varies with the developmental stage at the time of exposure to an adverse influence. There are critical periods of susceptibility to agents and organ systems affected by these agents.

23. The Six Principles of Teratology Wilson 1959 3. Teratogenic agents act in specific ways on developing cells and tissues to initiate sequences of abnormal developmental events. 4. The access of adverse influences to developing tissues depends on the nature of the influence. – nature of the agent – route and degree of maternal exposure – rate of placental transfer and systemic absorption – composition of the maternal and embryonic/fetal genotypes.

24. The Six Principles of Teratology Wilson 1959 5. There are four manifestations of deviant development 5. Death 6. Malformation 7. Growth Retardation 8. Functional Defect) 6. Manifestations of deviant development increase in frequency and degree as dosage increases from the No Observable Adverse Effect Level (NOAEL) to a dose producing 100% Lethality (LD100).

25. Teratogens Drugs and medications Environmental chemicals Ionizing radiation Infections Metabolic imbalance

26. Thalidomide Fetal Alcohol Syndrome Fetal Alcohol Spectrum Disorder

27. 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

28. Fetal Monitoring

29. Ultrasonography Monitoring: Chorionic sac during embryonic period placental and fetal size multiple births abnormal presentations biparietal diameter Uses reflection of very high frequency sound waves of between 3.5 to 7.0 megahertz (i.e. 3.5 to 7 million cycles per second)

30. 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. Today, in many perinatal care centers, fetal blood sampling is performed by specially trained perinatologists as part of diagnosing, treating, and monitoring fetal problems at various times during pregnancy.

31. 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.

32. 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

33. 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 Amniocentesis also referred to as amniotic fluid test or AFT

34. 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).

35. 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

36. Factors Affecting Fetal Growth

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

38. 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

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