The umbilical cord and placenta which were once considered unsanitary and were treated as infectious waste are now receiving much attention in the medical world. The reason behind this is that they have discovered abundant stem cells in them that can transform into various types of tissue. Particularly, cord blood, which is blood from the umbilical cord, contains blood-forming stem cells and mesenchymal stem cells that form bones, muscles, and organs; it is currently being studied for treatment of diseases, and some techniques have already been commercialized.
In 2000, a six-year-old girl named Molly living in the United States was suffering a fatal genetic disorder called Fanconi anemia. The only possible treatment was a stem cell transplant, but they could not find a matched donor for her. So they decided to use umbilical cord blood to treat her. It had been long since Molly’s cord blood was discarded, so Molly’s parents decided to have another baby to save Molly. That way, her younger brother, Adam, was born, and he saved her miraculously and gave happiness to his family.
Like this, umbilical cord blood can be used to treat some diseases, and it can give life to someone by culturing its stem cells. Collecting stem cells from cord blood is free from bioethical controversies because the embryo is not used for this process, and it has a strong ability to proliferate, which is why many people are curious to see the outcome of the study. The placenta also has all kinds of hormones and enzymes as well as stem cells, providing a ground for development of new medicine.
From the ancient times, the umbilical cord and the placenta were treated with care and regarded as symbols of life in some countries. In particular, during the Joseon Dynasty of Korea, the umbilical cord and the placenta of a royal baby born by the queen were not thrown away, but kept with care. They were kept in a small white jar and underwent a ceremony to be washed a hundred times seven days after the birth of the royal baby, and then they were wrapped in multiple layers, put in a bigger jar, and buried in a good location. The umbilical cord and the placenta were considered so precious that there were even records showing that some people got promoted for keeping the royal baby’s umbilical cord and placenta well and that some people got in trouble for treating them carelessly.
The placenta is a protective organ that helps the fetus survive and grow in the mother’s body by connecting the fetus to the wall of uterus. The fertilized egg becomes a saclike embryo after four or five days of fertilization. Then the inner part of the embryo grows to become a fetus, and the outer part of it becomes the umbilical cord and the placenta. After the fertilized egg implants in the uterus, the outer cells of the embryo change into what looks like bumps, burrow into the uterus lining by producing proteases, and find blood vessels and form tissue. Just as the roots grow deeper as the tree grows, the placenta also makes more blood vessels inside the womb as the baby grows.
The connection between the embryo and the uterus is weak in the beginning of pregnancy. However, as the placenta is completed, the fetus gets attached to the mom securely just like an anchored boat. The reason why the miscarriage rate drops dramatically after week 12 of pregnancy is because that is when the placenta is formed completely. Kangaroos and koalas give birth to their young prematurely because of the weak development of their placentas, and they raise their young in their pouches until they grow to a certain point.
The umbilical cord which starts from the belly of the fetus gets connected to the placenta, connecting the mom and the baby directly to serve as a medium in exchanging materials between them. The mom’s oxygen and nutrients are provided to the fetus, and the fetal waste such as CO₂ is transported to the mom. What is interesting is antibodies. During the first six months after birth, babies don’t easily get infectious diseases such as measles or the smallpox, because they are born with antibodies from their mothers. However, since not all maternal antibodies can pass through the placenta, they have no immune system to some diseases such as the whooping cough or the chickenpox.
Also, the placenta selectively lets other materials as well as antibodies pass through. In other words, it plays the role of a filter, letting beneficial materials pass through to reach the fetus and blocking harmful materials. Thanks to the placenta, the fetus has no problem surviving in the mom’s body even if they have different blood types. It is because the placenta filters red blood cells and antibodiesa1. Thanks to the placenta, although the mom catches bacterial infections, the baby doesn’t get infected.
1. Although the antibodies that recognize ABO types cannot pass through the placenta, the antibodies that recognize Rh types can pass through the placenta. Therefore, there can be a problem when an Rh-negative mother has a baby whose Rh factor is positive.
However, some drugs or tiny viruses can reach the fetus with serious impact on it. For example, small, fat-soluble molecules such as nicotine and alcohol can pass through the placenta and reach the fetus, which is why it requires extreme caution.
From the seventh month of pregnancy, the fetus can detect lights and shadows. When the mom feels the light, the melatonin secretion is reduced, and such change is conveyed to the fetus through the placenta. It means that the fetus can feel the light which the mom is looking at, without looking directly at the light outside the mom’s body.
The placenta not only plays the role of a medium but also produces nutrients and hormones that are necessary for the mother and the fetus. The nutrient from the mother is stored in the form of glycogen in the fetus, and an adequate amount is provided to the fetus each time. Therefore, even when the mom’s supply of nutrient is not consistent, the fetus can stably get nutrients. The placenta also provides the fetus with the combination of cholesterol and fatty acid as well as glycogen.
Also, it secretes human chorionic gonadotropin [hCG], which maintains pregnancy, in the first trimester of pregnancy. As it enters the second trimester of pregnancy, it secretes a large amount of progesterones and estrogens which develop the uterus, helps with smooth blood circulation, and keeps the uterus from contracting, and this way, it helps the fetus grow safely. The hormones that decide the time of delivery are also secreted from the placenta.
It has been a mystery for a long time how the placenta can exist in the mom’s body without decomposing. The immune system normally attacks the substances with different genes in order to protect the body. That’s why it is hard to understand how the placenta which is half from the mom and half from the fetus can exist.
Professor Phil Lowry at the University of Reading explained that it is possible because the placenta acts like a parasite to avoid attack by a mother’s immune system. As for parasites, the molecules called phosphocholines, which are present on the surface of their cells, trick a person’s immune system into recognizing them as its own cell. In the same way, most proteins synthesized in the placenta have phosphocholines, using the strategy to deceive the system of the mother’s body. The placenta, which is an organ solely for the fetus, comes out of the mom’s body with a light pain once the baby is born and its function is done after delivery.
The fetus that cannot do anything on its own grows inside the mom’s womb, and is born as a confident living being. This is possible thanks to the umbilical cord and the placenta which connect the mom and the baby. The mother’s body gives a secure nest to the fetus and with no condition everything necessary for the fetus to sustain its life, and takes in everything that becomes unnecessary.
All people born in this world have the mark of the umbilical cord that shows they were one with their moms. It is the belly button. From the moment a life begins to exist, the mom and the baby are connected together, forming an inseparable relationship.
- Reference
- Lee, Seong-gyu. “세종대왕과 태반의 수수께끼” [Sejong the Great and the Mystery of Placenta]. Dong-A Science, December 3, 2010.
- Kim, Jeong-hun. “엄마와 아기의 경계선, 태반의 신비” [Boundary between Mom and Baby, Mystery of the Placenta]. KISTI’s Science Scent, December 3, 2007.
- Lee, Eunhee. 하리하라의 바이오 사이언스 [Hari Hara’s Bioscience]. Korea: Sallimfriends, 2009.
- Park, Se-pil. 줄기세포 생명공학의 위대한 도전 [Great Challenge of Stem Cell Biotechnology]. Korea: Donga M&B, 2005.