Ashraf Fouda, MD

Articles

Vaccinations in Pregnancy

The Management of Tubal Pregnancy

Are Neonatal Encephalopathy & Cerebral Palsy Obstetric Malpractice?

Newborn Resuscitation

Meconium

 Origin:The placenta develops fromgthe chorion frondosum( foetal origin)and decidua basalis( maternal origin).


  Shape : discoid.
  Diameter : 15-20 cm.
  Weight : 500 gm.
  Thickness: 2.5 cm at its center and gradually tapers towards the periphery.
  Position : in the upper uterine segment (99.5%), either in the posterior surface (2/3) or the anterior surface (1/3).


  •  Foetal surface
  •  Maternal surface


•  Smooth, glistening and is coveredby the amnion which is reflectedon the cord.
•  The umbilical cord is inserted nearor at the center of this surface andits radiating branches can be seenbeneath the amnion.


•  Dull greyish red in colour andis divided into 15-20cotyledons.  
  •  Each cotyledon is formed ofthe branches of one mainvillus stem covered by deciduabasalis.


(1) Respiratory function  
  (2) Nutritive function
(3) Excretory function
(4) Production of enzymes
(5) Production of pregnancy associated plasmaproteins (PAPP)
(6) Barrier function
(7) Endocrine function


•  O2 and CO2 pass across the placenta by simplediffusion.  
  •  The foetal haemoglobin has more affinityand carrying capacity than adult haemoglobin.
•  2,3 diphosphoglycerate (2,3-DPG) whichcompetes for oxygen binding sites in thehaemoglobin molecule, is less bounded to thefoetal haemoglobin (HbF) and thereby allows agreater uptake of O2 ( O2 affinity).


  The rate of diffusion depends upon:
1. Maternal/ foetal gases gradient.
2. Maternal and foetal placental bloodflow.
3. Placental permeability.
4. Placental surface area.


  The transfer of nutrients from the mother tothe foetus is achieved by :  
  1. Simple diffusion : e.g. water andelectrolytes.  
  2. Facilitated diffusion: e.g. glucose.  
  3. Active diffusion: e.g. amino acids.
4. Pinocytosis: e.g. large protein moleculesand cells.


  Waste products of the foetusas urea are passed tomaternal blood bysimple diffusionthrough the placenta.


  e.g.:  
  •  Oxytocinase,  
  •  Monoamino oxidase,  
  •  Insulinase,  
  •  Histaminase and  
  •  Heat stable alkaline phosphatase.

(5) Production of pregnancy associated    l i (PAPP)    e g    plasma proteins e.g.
    •  PAPP-A,  
    •  PAPP-B, 
    •  PAPP-C,
    •  PAPP-D and
    •  PP5.   

 The exact function of these proteins is not    defined.

The foetal blood in the chorionic villi is    separated from the maternal blood, in    the intervillous spaces,    by the Placental Barrier    which is composed of :
1. Endothelium of the foetal blood vessels,    
    2. The villous stroma,    
    3. The cytotrophoblast, and    
    4. The syncytiotrophoblast.

(6) Barrier function:However, it is an incomplete barrier. 


  •  It allows the passage of antibodies(IgG only), hormones, antibiotics,sedatives, some viruses as rubellaand smallpox and some organisms astreponema pallida.
•  Substances of large molecular size asheparin and insulin cannot pass theplacental barrier.


    1- Human chorionic gonadotrophin (hCG)
    2- Human placental lactogen (hPL)
    3- Human chorionic thyrotrophin (hCT)
    4- Hypothalamic and pituitary like hormones
    5- Others as inhibin, relaxin and beta endorphins. 

1- Human chorionic    gonadotrophin (hCG)   

 - It is a glycoprotein produced by the    syncytiotrophoblast.
- It supports the corpus luteum in the first    10 weeks of pregnancy to produce    oestrogen and progesterone until the    syncytiotrophoblast can produce    progesterone.

1- Human chorionic    gonadotrophin (hCG)    HCG molecule is composed of 2 subunits

a. Alpha subunit:    which is similar to that of FSH, LH and TSH.    
    b. Beta subunit:    which is specific to hCG.

1- Human chorionic    gonadotrophin (hCG)    

•  HCG rises sharply after implantation,    reaches a peak of 100.000 mIU/ml    about the 60 th day of pregnancy    
    •  then falls sharply by the day 100 to    30.000 mIU/ml and is maintained at    this level until term.

The foetal blood in the chorionic villi is    separated from the maternal blood, in    the intervillous spaces,    by the Placental Barrier    which is composed of :1. Endothelium of the foetal blood vessels,        2. The villous stroma,        3. The cytotrophoblast, and        4. The syncytiotrophoblast.

Ashraf Fouda, MD

Articles

Vaccinations in Pregnancy

The Management of Tubal Pregnancy

Are Neonatal Encephalopathy & Cerebral Palsy Obstetric Malpractice?

Newborn Resuscitation

Meconium

Placenta and Umbilical Cord