AMNIOCENTESIS

By Patience Elett

Overview of Procedure

I. Introduction

Amniocentesis is an optional prenatal test that can establish whether or not your baby has certain genetic, mental, or physical disorders or defects. This is determined by analyzing a sample of the amniotic fluid while the mother is in her fifth month of pregnancy. Depending on the results, some families opt for an abortion. Amniocentesis can alert your doctor of physical defects which can be fixed before birth. The downside of amniocentesis is that it creates a chance of miscarriage. Amniocentesis is one of the most common prenatal diagnostic tools.

II. Before and During Amniocentesis Discovery

            Since the beginning of time, the inability to see or touch a fetus in a pregnant woman was a huge problem in obstetric care and in diagnosing mental and physical health issues of an unborn child. Before amniocentesis was discovered and available, prenatal tests were extremely limited and severely risky. By the late 1920s or early 1930s, amniocentesis was a rarely used but accepted procedure. The use of amniocentesis became widely used after Douglas Bevis got his article published in the February 1952 issue of Lancet. The study explained in this article was conducted at St. Mary’s Hospital in Manchester, England. His study included chemically analyzing the iron and urobilinogen content of amniotic fluid to determine the chance of hemolytic disease (blood disease) in prenatal children. He also used amniocentesis to judge prospective risks in the fetuses of Rh-negative women that were impregnated by Rh-positive men. Bevis’ article is seen as a tool for diagnosing maturity, health, and genetic defects in prenatal children. This technique was polished by another investigator in 1961 when they were published. This researcher measured amounts of bilirubin (a reddish-yellow natural compound made from hemoglobin) in the amniotic liquid of Rh-sensitized women.

III. What Amniocentesis Can Detect and Prevention of Defects

Eight weeks after conception, the prenatal child is about 2.5 centimeters long and has all of the anatomic elements it will have when it’s born. Diabetic mothers and mothers older than thirty-four have higher than usual chances of delivering babies who have birth defects. These are two of the reasons that amniocentesis is suggested to expecting mothers. 

Amniocentesis can be used to find out the sex of the baby. If the fetal cells contain a “Barr Body” (chromatin mass made of nucleic acid and protein on the edge of the nucleus [A complex body within a cell that contains the cell’s hereditary material and controls its growth]), then the fetus is female. Knowing the sex of the fetus is important in assessing the potential of a sex-linked (affects only one sex) disease when the child is born.

Amniocentesis can be used to rule out or diagnose uterine infections.

By measuring the level of AFP in the amniotic fluid, you can determine whether or not the fetus has neural tube defects such as spina bifida and anencephaly.

Amniocentesis can also detect over two hundred genetic disorders.

Amniocentesis detects nearly all chromosomal disorders in a fetus, and is more than 99% accurate with diagnostics.

Amniocentesis cannot detect other physical birth defects such as cleft lip or heart malformation.

If the lungs of the fetus are not mature enough to work properly after birth, a hormone can be administered to encourage development.

V. How Amniocentesis is Performed

            In the pioneering days of amniocentesis, doctors put the needle into the uterus guided only by touch and tried not to stick the placenta, the baby, or umbilical cord. Nowadays, ultrasound machines rule out that risk because doctors can see where everything is inside of the mother.  The mother is given a shot to numb the pain, and then fluid is taken from the amniotic sac and sent into the labs for analysis and culturing. This takes anywhere from ten to twenty days. The sample of amniotic fluid is typically about four teaspoons. The woman’s body will replenish the depleted supply of fluid. During early pregnancy, the amniotic fluid looks like blood serum. The amniotic fluid contains fetal cells from skin, and from the gastrointestinal, reproductive, and respiratory tracts.  Once the fluid is extracted, the fetal cells are separated out. Subnormal lecithin production in a prenatal baby typically indicates that the baby will have respiratory distress syndrome or hyaline membrane disease after birth. Both diseases have the potential to become fatal. Diabetic mothers commonly bear children with such troubles.

VI. Dr.

Douglas Bevis

Dr. Douglas Charles Aitchison Bevis, born May 28^th 1919, was an obstetrician, and a gynecologist. He was a consultant at Park Hospital, Manchester from 1952-1967. Then he was a reader in Obstetrics and Gynecology at the Sheffield University Hospital from 1967-1973. He then went on to be a professor of Obstetrics and Gynecology at the Leeds University Hospital from 1973-1984. He married and his wife bore him two sons. He died at Sheffield on June 25^th, 1994.  Dr. Bevis was one of the doctors included in a group trained in Manchester in the immediate post-war period who made a big contribution to obstetrics and gynecology. Bevis’ department was the first academic department in this specialty that was based at St. James’ Hospital, Leeds, and so Bevis set the main foundation for its accomplishment.

 VII. Journal Article Summary

            Amniocentesis in twin growth is uncommon for most medical centers. The technique used includes double needle penetration and inserting dye into the first amniotic sac. Now a new method is being proposed. It only takes one needle instead of two, and it doesn’t need any dye. It offers positive proof of tapping the gestational sacs. Although there are potential risks involved, the good outweighs the bad.

Bibliography

1. Jeanty, P., Shah, D., & Roussis, P. (1990). Single-needle insertion in twin amniocentesis. Journal of Ultrasound in Medicine, 9(9 511-517), Retrieved from

2.  Amniocentesis. (2010, July). Retrieved December 13, 2010, from babycenter website: http://www.babycenter.com/0_amniocentesis_327.bc?

3. Amniocentesis. (n.d.). Retrieved December 13, 2010, from Medical Discoveries website:
 http://www.discoveriesinmedicine.com/A-An/Amniocentesis.html

4. The First Test-Tube Baby. (1978, July 31). Time, 6. Retrieved from http://www.time.com/time/magazine/article/0,9171,946934-6,00.html

5. Amniocentesis (inventions). (n.d.). Retrieved December 13, 2010, from Crankshaft website: http://www.the-crankshaft.info/2010/04/amniocentesis.html

6. Crompton, A. C. (1994, July 30). Obituary: Professor Douglas Bevis . Retrieved from HighBeam Research website: http://www.highbeam.com/doc/1P2-4666571.html