It ensures vital exchanges in utero between mother and child, acts as a real filter against external aggressions … The placenta is the guarantor of the proper development of the fetus. How is it formed? How can it be a source of gestational complications? Explanations.

The placenta is the organ that is essential for a successful pregnancy. Its role: to allow nutrient and gas exchanges between mother and child, via maternal blood. It thus ensures the “food” and respiratory functions of the fetus while waiting for its digestive and respiratory systems to reach maturity at the time of birth. The placenta also plays a filter role, protecting the fetus against most of the external substances that are potentially harmful to it (heavy metals, etc.)

Even if it is not really functional until the fourth month of pregnancy, the placenta begins to form in parallel with the embryo from fertilization and the formation of the egg, a single cell born from the union between the sperm. and the ovum. Therefore, the trophoblast (the future placenta) develops in several stages.

• Segmentation and migration into the uterine cavity:

  During the first phase of cell division, the egg reaches the so-called morula stage approximately 72 hours after fertilization. Made up of a “cluster” of cells, it then looks like a blackberry (hence its name) which grows exponentially from day to day. From the sixth division (the morula is then composed of 64 cells), we can observe a differentiation between:

  – The central cells, the volume of which is greater, which will form the embryo,

  – Peripheral cells, smaller, which surround the central cells and will play a key role in the formation of the placenta.

• The blastocyst stage:

  Four days after fertilization, the morula evolves into a blastocyst and continues to migrate from the tube to the uterine cavity. At this stage, the peripheral cells tighten together to form the protective envelope of the embryo. They then form the trophoblast, part of which will later develop into the placenta. In the center of this envelope, a cavity filled with liquid (the blastocoel) and the embryonic button. Formed by the most central cells of the blastocyst, it caps the trophoblast to form the embryonic pole.

• Arrival in the uterus and implantation:

  Five days after fertilization, the embryo attaches itself to the uterine lining. It will then gradually penetrate there, “making its nest”. This is implantation which takes place 7 to 10 days after fertilization.

  During this second week of pregnancy, the future placenta develops at high speed:

  – to D9, the trophoblast divides into two: the cytotrophoblast and the syncytiotrophoblast, which evolves to form vacancies.

  – to D12, the small blood vessels in the uterine lining (capillaries) that surround the syncytiotrophoblast rupture and fill the gaps with blood.

  – to D13, the lacunae merge to bind the blastocyst and the maternal blood system. In parallel, the chorionic villi appear and surround the lacunae.

Until the end of the 3rd month, these very fine growths of the trophoblast develop, grow and branch out to facilitate exchanges between mother and baby. Around 4 months, the placenta is functional. It then continues to grow until the end of pregnancy when it weighs about 600 grams and covers a small third of the uterine surface.

Rather common (15 to 20% of pregnancies are affected), placental abruption is a potentially serious complication. Blood loss, severe uterine pain and hardening of the abdomen are symptomatic (in some cases) of this complication, the name of which changes during pregnancy. Thus, we are talking about:

• trophoblastic detachment until the 3rd month of pregnancy,
• placental abruption, starting in the second trimester.

Trophoblastic detachment is usually benign if the fetal vital signs are good. In the vast majority of cases, the hematoma causing the detachment resolves on its own and a normal continuation of the pregnancy can be considered, even if the usual medical recommendations generally involve a period of strict rest, a ban on carrying heavy loads and in some cases temporary sexual abstinence.

More frequent in the 2 nd and 3 rd trimesters of pregnancy, the detachment can also be more serious, especially when it is due to the appearance of a retroplacental hematoma. Of various origins, this type of hematoma is more common in women suffering from pre-eclampsia, hypertension, having suffered a shock / blow in the abdomen… or smoking! The normally inserted placenta then suffers from a loss of adhesion to the wall of the uterus and the exchanges between the mother and her baby no longer take place correctly. Result: acute fetal distress due to the drop in oxygen supply may appear, the vital prognosis of the baby and more rarely of the mother, engaged. Any symptom likely to recall a detachment and a fortiori any bleeding must therefore be the subject of an emergency consultation. Faced with the risks, an emergency cesarean section may be recommended if the fetus runs out of oxygen.

Rather rare (2,8 / 1000 pregnancies, nearly 4/1000 twin pregnancies), placenta previa describes poor positioning of the placenta, which is then implanted in the lower segment of the uterus. More common in the first trimester of pregnancy, it is usually detected by pelvic ultrasound following vaginal bleeding. The main risks associated with this complication: the threat of premature delivery (favored by the appearance of early contractions) or even bleeding during delivery (fortunately very rare) sometimes requiring a maternal transfusion.

 Factors promoting placenta preavia:

• the shape of the uterus
• smoking,
• mother’s age (35 and over),
• a scarred uterus (history of curettage, cesarean section, etc.),
• multiple pregnancies,

In the absence of treatment, very regular ultrasound and clinical follow-up is set up and strict rest until term is advised. Depending on the positioning of the placenta at the end of pregnancy, a cesarean section may be considered. Note however: vaginal birth is sometimes possible and is assessed on a case-by-case basis by the practitioner.

Popular in the countries of North America, placentophagy would fight against postpartum depression, stimulate lactation, reduce pain associated with childbirth and provide the mother with iron and minerals from the placenta. upon absorption. Cooked or packaged in capsules, the placenta would thus be, for its supporters, a real panacea to fight against small and major post-natal ailments.

For the scientific community and the American health authorities, the practice is on the contrary ineffective, even potentially dangerous. Indeed, eating the placenta would not only have no scientifically proven virtue, but could lead mothers to absorb heavy metals (lead, mercury) filtered by the organ during pregnancy. In addition, placentophagy is not without risk for the baby, as evidenced by a recent case of bacterial intoxication of a newborn, via breastfeeding, following the ingestion by his mother of capsules of placenta mal conditioned.

Note: in France, even if the texts do not officially prohibit placentophagy, eating your placenta is not authorized for two reasons. Not only, “the human body, its elements and its products cannot be the subject of a patrimonial right” (article 16-1 of the Civil Code), but the hospitals are responsible for collecting and incinerating the waste of ” care activities under penalty of incurring criminal penalties (articles R 1335-1 and following of the decree of October 22, 2010).