Pregnancy and placenta formation


Pregnancy is one of the wonderful experiences in a women`s life, in fact, to the whole family. The pregnancy in a human being is a very intricate but physiologically important process that needs a lot of supervision and assistance from the family and the practitioners. It is a long process as a healthy pregnant women need to wait for an average of 9 months for her delivery. Pregnancy is scientifically divided into 3 trimesters; the first trimester comes in the first 3 months from the time of conception and the second trimester falls between 4-6 months of pregnancy while the rest of the period (7-9 months) is the third trimester. During pregnancy, a woman experiences a lot of hormonal, anatomical and physiological changes and adjustments within her body and one of the most prominent parts of this is the morning sickness.  However, at this stage, we do not discuss about the signs and sym[toms of pregnancy in detail, let us focus on one of the important structural and functional component of pregnancy, the placenta. 



Functions of the placenta

The placenta is the junction between the mother and the growing fetus. It acts as a physiological bridge between the baby and the mother allowing the baby to receive a lot of elements from the mother. In fact, it is the lifeblood of a growing embryo because almost every necessities of the baby are dealt with by the placenta. Placenta assists in many functions. Firstly, it attaches the developing fetus to the mother`s uterine wall through the umbilical cord. The blood supply to the placenta allows nutrient uptake, regulation of body temperature of the baby, elimination of wastes and carbon dioxide gas from the baby`s body. It is also instrumental in fighting against foreign invaders such as bacteria, virus and many other materials that affect the growing fetus is safe.  Another major function of the placenta is the production of pregnancy-related hormones and their regulation. he placenta is the most vital component of pregnancy for both the mother and baby.  It helps to trap a number of toxic chemicals so that the growing baby is safe inside. It also helps in metabolizing a number of substances so that they are released the fetal circulation.



Surfaces of placenta

As the placenta grows, it develops many tiny hair-like villi that penetrate the decidua( inner uterine wall) so that the embryo is firmly attached to the mother. A typical placenta has 2 surfaces, namely, maternal placental surface and the fetal placental surface. The maternal surface is a junction between the umbilical cord and mother whereas the fetal surface is the linkage between the umbilicus and the placenta where umbilicus is the main mediator that connects the 2 surfaces.


Formation of placenta

 The placenta is a temporary structure because it is expelled after the birth of the baby.  The formation of the fetus commences upon the implantation of the blastocyst after the fertilization. A mass of undifferentiated cells in the early stage of pregnancy leads to the formation of what is known as the blastocyst. The external layer of the blastocyst becomes the trophoblast which eventually modified into many layers of the placenta. The outermost layer of the placenta is the chorion which comes into contact with the endometrium. It is composed of two layers of cells; the inner cytotrophoblast and outer syncytiotrophoblast cells. The chorion and allantois fuse to form the chorioallantoic membrane. The development of the placenta is a continuous process throughout the pregnancy however, the development of the maternal side is completed by week 14.



Placenta attached to umbilical cord-image from google




Abnormalities of placenta

  1. Placenta Accreta is the abnormal adherence of placenta with the absence of decidua basalis. It is common in women with previous cesarean.
  2. Placenta increta is the deeper attachment of the placenta into the uterine wall, consequently, it penetrates into the uterine muscle, but does not penetrate the uterine serosa. 
  3. Placenta percreta is a condition where placental villi penetrate myometrium to lead to the uterine serosa.
  4. Placenta Previa is when the placenta overlies internal os of the uterus which essentially covers the whole birth canal. It is one of the cause of chronic bleeding and often treated as an emergency.
  5. Vasa Previa is a  placental abnormality where the fetal vessels rest within the membranes close to the inner cervical os (opening). 
  6. Abruptio Placenta is the formation of abnormal blood clots at the retroplacental region making the delivery difficult.
  7. Hydatidiform mole is a  placental tumour without the involvement of embryo. Some of the most common forms of mole arepartial mole, complete mole and persistent gestational trophoblastic tumors. 




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