By: Shankavi Suthaparan
Identical twins occur when one fertilized egg divides into two individuals, with the exact same genetic information. Some women have a greater chance of giving birth to twins due to certain factors. Typically, women in their 30s and 40s have higher estrogen levels than younger women, allowing them to produce more than one egg at a time. It may also be a hereditary factor, where a woman is more likely to give birth to twins if there are already twins in her family. Conjoined twins are twins born physically attached to each other. They are believed to develop when the embryo only splits partially, failing to separate completely as it divides. Although the two individual fetuses will continue to develop from the embryo, they remain physically connected to one another.
Some twins only share a small amount of tissue, and could have all the organs and parts they need to live, while others may share one or more internal organs. According to statistics, conjoined twin births occur once every 200,000 live births. Many are born as stillborns, or die a short period after they have been given birth to. However, due to certain medical advancements in fetal surgery and technology, survival rates have improved significantly. Depending on exactly where the twins are conjoined, and which organs the two share, some surviving conjoined twins could be surgically separated. They have been known to be conjoined at either the chest, abdomen, spine, pelvis, or the head. The chest is one of the most common sites of conjoined twins, where they share a heart, and may share a liver and upper intestine. When conjoined at the base of the spine or pelvis, they have to share their lower gastrointestinal tract, and may share their genital and urinary organs. At the head, twins would be conjoined either at the back, top or side of the head, sharing a fragment of their skull and some brain tissue. Their brains however are usually separate. Cases where twins are born sharing a brain have been shown to rarely survive.
Pregnancy with conjoined twins is extremely complicated, and can drastically increase the risk of complications. When giving birth, they require a C- section, due to their complex anatomy. It is likely that conjoined twin babies are born prematurely, and may have breathing or heart problems immediately after they are born. There are also rare cases of asymmetric conjoined twins, where one twin is much smaller or partially developed compared to the other. This twin is called the parasitic twin, and cannot survive without its twin. Without any treatment, the twin may form many health problems, as it is supporting its parasitic twin as well.
Although the birth and survival rate of conjoined twins are low, there are so many healthy cases in our world today. As medical research expands, and our technology grows, we can hope to learn more in the near future.
References:
“Conjoined Twins - Symptoms and Causes.” Mayo Clinic, 2019,
www.mayoclinic.org/diseases-conditions/conjoined-twins/symptoms-causes/syc-2035390. Accessed 12 Nov. 2021.
“Conjoined Twins.” Seattle Children’s Hospital, 2016,
www.seattlechildrens.org/conditions/conjoined-twins/. Accessed 12 Nov. 2021.
“Conjoined Twins Fast Facts.” CNN, CNN, 11 July 2013,
www.cnn.com/2013/07/11/world/conjoined-twins-fast-facts/index.html. Accessed 12
Nov. 2021.
Pietrangelo, Ann. “What Is a Parasitic Twin?” Healthline, Healthline Media, 20 Feb. 2019, www.healthline.com/health/pregnancy/parasitic-twin. Accessed 12 Nov. 2021.
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