In chapter six, "The Best-Laid (Body) Plans," Neil Shubin briefly discusses the dangers of a blastocyst implanting in sites other than the uterus, such as in the fallopian tubes, or even in the outer lining of the rectum, where the fetus can "develop to full term" (Shubin 100). Has this been a major issue for humans, and how would a doctor deal with this situation? Is it possible for the baby to grow in a site other than the uterus, and still be healthy? What are some documented cases on this, and how were they resolved? Over time, is it possible that implantation will somehow improve where it can be more accurate, and rare cases like this could be prevented?
Kathy Li, kathy2132@gmail.com
There is a designated place for the egg to divide and mature in women, called a uterus. However, the egg may not always implant in the uterus for many reasons. This situation is called ectopic pregnancy where the egg implants in one of the fallopian tubes and develops there (Ectopic Pregnancy). Today, about 2% of all pregnancies turn out to be ectopic (Sepilian), and it “ultimately ends in the death of the fetus” (Sepilian).
ReplyDeleteThe first reason that this happens is due to a problem in the fallopian tubes. This is the site of conception where the sperm and egg meet. The egg then travels through these tubes and into the uterus. If the tubes are infected from surgery or tumors then there is a greater chance that the egg will not be able to fertilize or make its way completely. (Ectopic Pregnancy).
A second possible reason is that the mother could be exposed to drugs such as diethylstilbesterol, DES, which is given to prevent miscarriages for women since 1938. Until 1971. women took these pills without knowing that they could “cause vaginal and cervical cancer in the daughters of the women who took the pill” (Ectopic Pregnancy). Research proved that the daughters would have “anomalies in their reproductive tracts, infertility and poor pregnancy outcomes” (Ectopic Pregnancy). This condition can be passed down; if those women grow up to have daughter, the likelihood of them having reproductive problems are very high.
Intrauterine contraceptive devices are the most common causes of ectopic situations. These devices which are implanted into the uterus help prevent pregnancy but for some reason if one gets pregnant, the chances of the implantation in the fallopian tubes are also very high. Also, women who have after tubal sterilization are at high risk if the procedure fails. This is where the “fallopian tubes are cut, tied, or burned, in order to
prevent further pregnancies”. (Ectopic Pregnancy)
Not only the egg can implant in the fallopian tube, but in other places like the abdominal wall, the cervix, or the ovary. These conditions are very, very rare. These “alternative” sites are not healthy at all because the growing embryo will not have the proper environment and nutrition.
Ectopic pregnancies can be treated through surgery and drugs. It is very rare for the egg to survive for more than 5 to 8 weeks because the mother can experience severe abdominal pain and vaginal bleeding that requires immediate treatment. Drugs such as methotrexate is used which stops the growth of the embryo. If this pregnancy goes too far and the mother has a rupture fallopian tube or cannot be monitored appropriately which the drug is given, then surgery is done to remove the embryo. (Ectopic Pregnancy)
This situation is related to the theme Structure and Function because if the structure of the fallopian tubes or the uterus is not suitable for the egg, then it will not be able to do its function by properly housing and nourishing the egg.
Chandrika D.
(shiningstar0393@gmail.com)
“Ectopic Pregnancy – A Dangerous Pregnancy Outside the Uterus”. Retrieved March 29,
2011, from
http://www.diseaseaday.com/reproductive-system/ectopic-pregnancy-a-dangerous
-pregnancy-outside-the-uterus
Sepilian, Vicken P. “Ectopic Pregnancy”. Retrieved March 29, 2011, from
http://emedicine.medscape.com/article/258768-overview
As Chandrika said, the uterus is made for the egg to properly implant and develop into a fetus, but sometimes an error occurs and the baby or mother can die as a result of the error. Although most ectopic pregnancies occur in the fallopian tubes, as Chandrika said, they can also occur in the ovary, stomach area, or cervix. Regardless of where the abnormal pregnancy occurs, the baby is unable to survive and often doesn’t even develop as a result. The incorrect implantation often occurs as a result of a blockage that slows the movement of the egg through the fallopian tube, either because of hormones that form a physical blockage or other factors such as smoking.
ReplyDeleteAn ectopic pregnancy cannot be allowed to continue the full term, because the developing cells endanger the mother’s life. Although this condition is treatable, only 1/3 of women who have an ectopic pregnancy are able to get pregnant again. If treated early, a women increases her chances of getting pregnant again. (http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001897/)
In special and rare cases, women have been able to carry their baby full term in an ectopic pregnancy. In one isolated case, the baby was was nourished with blood from the hypertrophied ovarian vessels on the right side. The mother’s uterus had to be amputated, but both the mother and child were healthy. Though this is one such case of a successful ectopic birth, the risk to both the child and mother are extremely high, and doctors do not recommend that mothers with an ectopic pregnancy continue carrying their baby. (http://www.ncbi.nlm.nih.gov/pubmed/1251665)
Since this is such a rare condition, humans won’t evolve to prevent these rare cases. These cases occur because of certain risk factors and also due to chance and error, so no over time we won’t see implantation improve unless mothers address their specific risk factors. If a population wishes to decrease their risk of having an ectopic pregnancy, they must directly address the causes. Pelvic inflammatory disease is the most common cause of ectopic pregnancies. Organisms, such as Neisseria gonorrhoeae and Chlamydia trachomattis attack the fallopian tubes, causing infections that later cause inflammation. Smoking also causes ectopic pregnancy, because it affects the cilia in the fallopian tubes, which move the egg along. When these cilia are impeded by smoking, the egg moves much slower and have a greater risk of getting “stuck” in the tubes. (http://www.aafp.org/afp/20000215/1080.html)
Anna Leng (annaissbananas@gmail.com)
In a normal pregnancy, the blastocyst is implanted into the woman’s uterus. However, there are some rare cases of pregnancies where the blastocyst implants outside the uterus. This is called an ectopic implantation. These types of pregnancies are very dangerous for the mother and the baby. In these pregnancies, the blastocyst usually implants in the fallopian tubes. This would be called a tubal pregnancy. However, sometimes in very rare cases, the ball of cells implants in the ovary, the cervix, or the belly, as Chandrika and Anna stated. Also, in rare cases, “the blastocyst is expelled into the mother’s body cavity, the space between her guts and body wall…or implanted on the outside lining of the mother’s rectum or uterus and the fetus develops to full term” (Shubin 100). That last case is very rare however, because usually the fetus is not able to develop fully if it is implanted anywhere except the uterus. There are many causes to this type of pregnancy occurring, as Chandrika and Anna explained. The main cause is that the fallopian tubes would be damaged. The fertilized egg would have more trouble travelling through the tubes and so it would just implant itself in the tubes. This could be caused by many things. Firstly, smoking can cause damage to the fallopian tubes. Other causes that increase a person’s risk for an ectopic implantation are pelvic inflammatory disease, endometriosis, which causes scar tissue in and around the fallopian tubes, having previous surgery inside the abdomen, or use of fertility medications at the time of conception. However, if a person has any of these “problems” or has experienced any of these factors it doesn’t necessarily mean they will have an ectopic implantation. This is because these pregnancies are extremely rare, making it very hard to be able to prevent even the small amount of them that do occur.
ReplyDeleteWhen the blastocyst implants in a place other than the uterus, the damage could be deadly. If the egg were to keep growing in the fallopian tubes, the tubes could burst and cause heavy bleeding. The most serious complication of an ectopic pregnancy is intra-abdominal hemorrhage, or severe bleeding. Because of these effects, most of these ectopic pregnancies have to be terminated because the fetuses would be severely damaging the mothers as both Anna and Chandrika discussed. These pregnancies are not necessarily a big issue for humans because they occur so rarely. However, when they do occur, they can be a very big and dangerous issue for the mother carrying the fetus. Also, because they so rarely occur, it is much more difficult to be able to find a way for them to be prevented. Because of this I agree with Anna when she said that “over time we won’t see implantation improve unless mothers address their specific risk factors”. Humans won’t evolve over time with ways to prevent these pregnancies because they are too rare.
Sources:
http://www.webmd.com/baby/tc/ectopic-pregnancy-topic-overview
http://www.emedicinehealth.com/ectopic_pregnancy/page6_em.htm
Danielle Webb (dwebb456@gmail.com)