In the simplest of words, a placenta whose maternal part is shed during childbirth is known as a deciduate placenta. It is mainly seen in a lot of mammals such as humans, cats, dogs, and so on and so forth. A more complicated definition would be that a deciduate placenta is a placenta in which the layer known as decidua is cast-off during childbirth along with the foetal placenta. 

The placenta is a crucial organ that is temporary and is developed a short time after implantation and persists throughout pregnancy, and in certain mammals, is shed with the child during childbirth. It is an endocrine organ, meaning the main purpose of the placenta is to create hormones and secretions that will serve to initiate the functions of other organs. 

The placenta is developed from the blastocyst shortly after implantation and is crucial as it promptly carries out the gas, waste, and nutrient exchange between the maternal and foetal circulations as they are physically separated. Another purpose of the placenta is to produce hormones during pregnancy that help to regulate the physiology of both the mother and the foetus.

Deciduate as a classification of placenta

The placenta can be classified into three types based on the degree of intimacy. These three types are deciduous placenta or placenta vera, non-deciduous or semi placenta, and also contra deciduate placenta.

Taking a brief look at these three classifications will help us understand the deciduate placenta better.

• Semi placenta or non-deciduous placenta – In mammals where the blastocysts are located in the uterine cavity, the implantation is superficial. This type of placenta is seen mainly in pigs, horses, and cattle, and in this, at the point of contact with the uterus, the blastocyst surface has finger-like projections, which are known as chorionic villi that are loosely united and penetrate into the uterine wall. 
• Placenta Vera or Deciduous Placenta –This occurs in the case of certain mammals, such as cats, dogs, primates, rodents, et cetera, and in this case, the degree of intimacy if the chorionic villi and the endometrium are much higher. It happens so that the uterine wall does not remain intact during the parturition as a high amount of corrosion of the uterine wall takes place. What happens, as a result, is the tearing away of the placenta, and this is followed by intense haemorrhage. This is known as true placenta or placenta vera, and it is shed during childbirth. This process of the shedding of the placenta is known as decidua.

• Contra deciduate placenta – Last but not least, this type of placenta is seen in the two species of moles, such as parameles and Talpa, and what happens is that both the maternal and foetal portion of the placenta is shed during childbirth. This is known as contra deciduate placenta.

Development of the deciduate placenta

The specialised layer of the endometrium that forms the bed of the placenta is known as the decidua. Endometrial stromal cells that undergo vascular modifications and cellular alterations known as “decidual reactions” are induced by progesterone, which is, in turn, produced by the corpus luteum of the ovary. The process of the development of the decidua, which is a modified mucosal lining of the uterus, and which forms in preparation for pregnancy, is known as decidualization. It is formed under the influence of progesterone. 

The function of the decidua

It can be comprehended easily that the deciduate placenta plays an important role in the reproductive system of animals that do contain it. So far, it has been known that it is shed during childbirth. However, it plays other important roles as well, such as the provision of nutrition, exchange of crucial gases, production of hormones, and, lastly and most importantly, regulation of syncytiotrophoblast invasion.

Anterior Placenta

When the placenta attaches itself to the front wall of the uterus, it is known as an anterior placenta. An anterior placenta has no link whatsoever to a low-lying placenta. A low-lying placenta, which is scientifically known as placenta praevia, is when the placenta is formed much lower and covers the opening of the cervix partially or entirely. 

The best way to know whether one has an anterior placenta is by undergoing a USG, that is, an ultrasound scan, when one is 18-21 weeks pregnant. Now, a very common question that arises regarding an anterior placenta is: “Are anterior placentas dangerous?”. It is thought so because it is believed that they give rise to complications. However, it is highly unlikely that they will give rise to any complications. 

The front of the abdomen is a very common and normal place for the development of the placenta, and it serves all the normal purposes of a normal placenta. However, a scan would be best to be sure about the absence of any major dangers. Thus, an anterior placenta is not a major cause of concern. However, it might become difficult for the mother to feel the movements of the foetus, and thus, it should be diagnosed, and the advice of a physician is recommended.

Conclusion

The deciduate placenta performs major functions during pregnancy, and it is one of the most important parts of the female reproductive system. Other than being shed during childbirth, it also helps to connect the foetus to the maternal system and helps greatly in the development of the foetus.