1. Placental Functions and Factors Affecting Fetal Growth

5. Circulatory adjustments at Birth
Topic will be covered in the later lecture on the cardiovascular system

6. 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

7. Placenta
Metabolism
Transfer
Endocrine

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

9. 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

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

11. 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

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

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

14. Dizygotic Twins

15. Dizygotic Twins

16. Monozygotic Twins

17. Monozygotic Twins

18. Conjoined Twins

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

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

22. Teratogens
External agents that cause congenital malformations

23. The Six Principles of Teratology Wilson 1959
Susceptibility to teratogenesis depends on the genotype of the conceptus and the manner in which this interacts with adverse environmental factors.
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.

24. The Six Principles of Teratology Wilson 1959
Teratogenic agents act in specific ways on developing cells and tissues to initiate sequences of abnormal developmental events.
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.

25. The Six Principles of Teratology Wilson 1959
There are four manifestations of deviant development
Death
Malformation
Growth Retardation
Functional Defect)
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).

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

27. Fetal Alcohol Syndrome
Thalidomide
Fetal Alcohol Syndrome
Fetal Alcohol Spectrum Disorder

28. 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

29. Fetal Monitoring

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

31. 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.

32. 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.

33. 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 way

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

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

36. 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

37. Factors Affecting Fetal Growth

38. Placental Insufficiency
Placental defects effectively reduce available surface area
reduced uteroplacental blood flow may also occur due to maternal hypotension or renal disease.
Mount Sinai Hospital – Toronto – Placental Insufficiency

39. 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

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