Background

Amniocentesis is a diagnostic medical procedure. It was founded in the mid-20th century. It is developed to obtain information about the chromosomal health and genetic health of a developing fetus during pregnancy. The procedure includes the extraction of a little amount of the amniotic fluid from amniotic sac of the developing fetus. The amniotic fluid contains cells which are shed by a developing fetus. The analysis of amniotic cells will provide important information about chromosomal abnormalities, genetic disorders, and certain birth defects.

Between the 15th and 20th week of pregnancy, Amniocentesis is performed. It is suggested for women with a high risk of having a child with a genetic condition. With advancements in technology and medical understanding, amniocentesis has been made safer and more accurate over the years. This can make it a valuable procedure in prenatal care to assess the health and well-being of a developing fetus.  

Indications

• Advanced Maternal Age: Women whose age is 35 years and older at the delivery time have a high risk of chromosomal abnormalities like Down syndrome in their offspring. 
• Abnormal Maternal Serum Screening: Increased levels of specific markers in maternal blood screening tests can suggest an elevated risk of chromosomal abnormalities or neural tube defects. 
• Previous Child with Chromosomal Abnormality: If an earlier pregnancy resulted in a child who has chromosomal abnormality, amniocentesis can be suggested in subsequent pregnancies.  
• Family History of Genetic Disorders: A family history of specific genetic conditions or chromosomal abnormalities can elevate the chances of such conditions in the current pregnancy. 
• Abnormal Ultrasound Findings: An ultrasound revealing structural abnormality or soft markers linked with genetic conditions can need urgent diagnostic testing by amniocentesis. 
• Known Genetic Carrier Status: If one or both of the parents are carriers of a specific genetic disorder, amniocentesis can be performed to assess whether the fetus has an inherited condition or not.  
• Parental Anxiety or Request for Information:  Parents can opt for amniocentesis because of the increased anxiety or a strong will for more comprehensive information about the health of the fetus in some cases.  

Contraindications

• Active Maternal Infection: If a pregnant woman has an active infection, specifically in the urinary tract or genital tract, the risk of introducing bacteria into the amniotic fluid is a concern during the procedure.  
• Ruptured Membranes (Preterm Premature Rupture of Membranes, PPROM): If amniotic sac has ruptured prematurely, the procedure can have increased risk of infection to both fetus and mother. 
• Placenta Previa: Amniocentesis is contraindicated in the presence of placenta previa. It is not suggested in the presence of placenta previa as it can lead to risk of bleeding. 
• Uterine Abnormalities or Fibroids: Conditions like uterine abnormalities or large fibroids can elevate the potential risks and difficulties linked with amniocentesis. 
• Multiple Pregnancies: Pregnancy which involve more than one fetus can increase the complications like injury to one of the fetus. 
• Maternal Coagulopathy or Bleeding Disorders: Conditions which can affect the blood clotting or lead to bleeding disease can increase the risk of excessive bleeding during or after the procedure.  
• Allergy to Local Anesthetics or Antiseptics: Allergic reactions to the compounds that are used during the procedure, like antiseptics or local anesthetics, may have a contraindication.  

Outcomes

• Genetic and Chromosomal Information: Amniocentesis can provide specific genetic information about the fetus by analysing the fetus cells from the amniotic fluid. This information can detect the chromosomal abnormalities like trisomy 18, trisomy 13, and Down syndrome. 
• Neural Tube Defect Detection: The procedure can detect the neural tube defects like spina bifida by analysing the level of specific markers in amniotic fluid. 
• Inherited Genetic Disorders: For couples who have risk of specific genetic disorders, amniocentesis can indicate whether the fetus got inherited the genetic condition. 
• Confirmation or Refutation of Screening Test: Amniocentesis may confirm or refutation of abnormal findings in previous screening test which provide more accurate information about the health of fetus.  
• Gender Determination: Amniocentesis can determine the sex of the fetus. It may be relevant for specific genetic conditions which are linked to gender or for any personal reasons.  

Periprocedural Evaluation

• Physical Examination: It includes medical history, any relevant genetic or familial factors, or obstetric history of patient. A physical examination of overall health of woman and any potential contraindications will assess. 
• Gestational Age Assessment: Assessment of gestational age to make sure that the procedure is performed in the proper stage of pregnancy.  
• Ultrasound Examination: An ultrasound examination can be performed to verify the position of fetus, the amount of amniotic fluid, and the location of placenta to guide the amniocentesis needle to place in proper position. 
• Laboratory Tests: Routine blood tests can be conducted to determine the blood type of woman, Rh factor and to check any infections which can have a risk during the procedure.  
• Counseling and Informed Consent: Informative counseling about the procedure, benefits, risks, and potential outcomes is necessary. Obtain informed consent from the pregnant women after providing all the information. 

Equipment

• Fluid Balance and Postoperative Care Ultrasound Machine: It is used to see the fetus and direct the needle insertion procedure.  
• Sterile Supplies: Drapes, sterile gloves, and gowns are necessary to maintain aseptic conditions during the procedure.  
• Needle and Syringe: A thin-gauge and sterile needle is used to extract the amniotic fluid. A syringe collects the sample from the fetus.  
• Local Anesthetic: Local anesthetic like lidocaine is used to numb the skin at insertion site. 
• Antiseptic Solution: An antiseptic solution like chlorhexidine or iodine is used to clean the skin before the procedure.  
• Laboratory Collection Tubes: Sterile tubes are used to collect and store the amniotic fluid sample. 
• Bandages and Dressings: Sterile dressings and bandages are used to cover the insertion site after the procedure.  
• Procedure Tray: A procedure tray is used to contain all the necessary sterile instruments for the procedure.

patient preparation and monitoring

• Informed Consent: Take informed consent after counseling about the procedure, purpose, risks, and benefits.  
• Explanation and Education: Provide detailed information to the women about the procedure, which includes the steps and what to expect during and after the procedure.  
• Gestational Age Confirmation: Verify the gestational age via ultrasound to make sure the procedure is performed at a proper stage of pregnancy. 
• Empty Bladder: Tell the woman to empty her bladder before the procedure for good visualization during ultrasound. 
• Positioning: Help the woman in a comfortable and proper position on the examination table. The position can vary but most common, woman lying on her back with the exposed abdomen. 
• Skin Preparation: Clean the skin with an antiseptic solution like chlorhexidine or iodine to lower the risk of infection. 
• Local Anesthesia: Local anesthesia, like lidocaine, is administered at the insertion site to reduce the discomfort during the needle insertion. 
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Monitoring During Amniocentesis

• Ultrasound Monitoring: Use ultrasound to assist the procedure, to make sure the accurate needle placement and lower the risk of injury to fetus. 
• Vital Signs Monitoring: Regularly monitor the vital signs of the patient, which include heart rate, blood pressure, and respiratory rate.  
• Patient Comfort: Assess the comfort level of patient continuously and address any discomfort or concerns properly.  
• Communication: Keep an open communication with the patient during the procedure, inform her of each step and make sure that she can understand. 
• Procedural Monitoring: Monitor the progress of amniocentesis and make sure that the correct amount of amniotic fluid is collected. 

TECHNIQUE

Step: 1 – Approach: 

Patient Positioning: The patient usually lies on her back with an exposed abdomen. 

Ultrasound Guidance: An ultrasound is used to see the fetus, amniotic fluid pockets, and assist in the procedure. 

Step: 2 – Skin Preparation: 

Cleaning: The skin of the abdomen is cleaned with an antiseptic solution to lower the risk of infection. 

Step: 3 – Local Anesthesia: 

Administration: Local anesthesia like lidocaine is administered into the skin and underlying tissue at the needle insertion site. 

Step: 4 – Needle Insertion: 

Ultrasound Guidance: A thin, sterilized needle is inserted into the abdominal wall and into the amniotic sac by using a real-time ultrasound. 

Avoidance of Fetal Injury: Take care to avoid the contact with the placenta, fetus, and umbilical cord during the insertion of needle.  

Step: 5 – Amniotic Fluid Collection: 

Withdrawal: A syringe is attached to the needle and a small amount of amniotic fluid is withdrawn. Usually, 20 ml of fluid is taken out. 

Collection in Sterile Tubes: The collected sample is transferred into a sterile collection tube for analysis.  

Step: 6 – Removal of Needle: 

Careful Withdrawal: The needle is carefully removed, and pressure is given on the insertion site to reduce the risk of bleeding. 

Genetics and Chromosomal Analysis

• Cell Culture: The cells are collected from the amniotic fluid. They are cultured to increase their numbers. 
• Chromosomal Analysis: Chromosomal analysis, like karyotyping, is carried out on the cultured cells to check for genetic abnormalities. 

Fluorescence In Situ Hybridization (FISH)

• Rapid Analysis: FISH can be performed for rapid analysis of specific chromosomal abnormalities without the need for cell culture in some cases.  

Fetal Lung Maturity Assessment

• Testing: Amniotic fluid can be tested for the presence of specific substances like surfactant proteins or phospholipids to check the maturity of lung in fetus. 
• Indication: This assessment is particularly important if there is a preterm delivery. 
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Premature Rupture of Membranes (PPROM)

• Risk Assessment: The risk of PPROM is taken into care before performing amniocentesis, specifically if there is any history or signs of weakened membranes. 
• Monitoring: The patient can be monitored closely after the procedure if there is any signs of PPROM and precautions are taken to reduce the risk. 

Complications

• Miscarriage: The risk of miscarriage with amniocentesis is a concern, although it is considered low. The rate of miscarriage linked to amniocentesis is below 1 %. 
• Infection: There is a risk of infection, despite the amniotic fluid is sterile. Infection may occur if bacteria are introduced during the procedure.  
• Vaginal Bleeding: After amniocentesis, some woman can experience mild vaginal bleeding. This is minimal and resolves on its own. 
• Leakage of Amniotic Fluid: The amniotic sac can be punctured during the procedure, which can lead to leakage of amniotic fluid in rare cases. This may lead to complications like infection or preterm labor. 
• Rh Sensitization: Rh-negative women can develop antibodies against Rh-positive blood cells if there is combination of maternal and fetal blood during amniocentesis. Rho(D) immune globulin (RhoGAM) is administered to prevent Rh sensitization. 
• Needle Injury: There is a low risk of injury to the fetus or around the structures by an amniocentesis needle. This risk is reduced by ultrasound guidance during the procedure.  
• Allergic Reaction: Some individuals can be allergic to compounds used during the procedure, like medications or antiseptic solutions. Allergies are rare but may occur. 

Medication Summary

• Local Anesthetic: Lidocaine or any other local anesthesia is used. It is administered at the insertion site to numb the area and minimize the discomfort during the needle insertion. 
• Antiseptic Solution: Chlorhexidine or iodine solution is used as an antiseptic solution. It is used to clean the skin over the abdomen to lower the risk of infection. 
• Analgesics: Acetaminophen or other mild analgesics are used to manage any post-procedural pain or discomfort.  
• Anti-anxiety Medications: Benzodiazepines like lorazepam or other anti-anxiety medications are used if the patient is experiencing anxiety or stress which are related to the procedure.  

Immune Globulins

Rho(D) immune globulin (RhoGAM) is not directly administered during amniocentesis. It is suggested in specific conditions to prevent Rh isoimmunization. Rh isoimmunization develops when Rh-negative mother is exposed to Rh-positive fetal blood. This can lead to development of antibodies which can have risk in subsequent pregnancy. 

Rh-negative Pregnant Women: Rh-negative women can get Rho(D) immune globulin during pregnancy. She can also get it after procedures like amniocentesis to prevent the development of Rh antibodies. 

Preventing Rh Isoimmunization: 

Amniocentesis has a risk of combining the maternal and fetal blood and if the fetal blood has Rh-positive and mother has Rh-negative, then there is a risk of sensitization. 

RhoGAM is administered to Rh-negative pregnant women within 72 hours after the amniocentesis or other procedure which may expose the fetal blood o mother blood to reduce the risk of Rh isoimmunization. 

RhoGAM prevents the development of Rh antibodies in Rh-negative mothers, reduce the risk of hemolytic disease of newborn (HDN) in subsequent pregnancy. It is preventive measurement in the situations where there is a risk of combination of maternal and fetal blood like chorionic villus sampling (CVS), amniocentesis, or any other procedure which have a risk of Rh sensitization.  

References

Amniocentesis – StatPearls    

Amniocentesis – nhs.uk 

Medication

Medication

References

Amniocentesis – StatPearls    

Amniocentesis – nhs.uk