Cordocentesis Test: Purpose, Test Details & Results

Cordocentesis, also known as percutaneous umbilical blood sampling (PUBS), is a specialized prenatal diagnostic procedure that provides direct access to fetal blood. This test is most often performed during the second and third trimesters of pregnancy to diagnose, monitor, or treat various fetal conditions. For expecting parents facing complex prenatal questions, understanding the purpose, procedure, and meaning of cordocentesis results is crucial to making informed decisions. This article unpacks the latest evidence to explain why and how cordocentesis is used, what to expect from the test, and how results guide follow-up care.

Purpose of Cordocentesis Test

Cordocentesis is a vital prenatal procedure that helps clinicians obtain fetal blood samples directly from the umbilical cord. The test is typically reserved for scenarios where other, less invasive procedures (like amniocentesis or chorionic villus sampling) may not provide the necessary information or when an urgent diagnosis is needed. Understanding the specific reasons for which cordocentesis is recommended can help patients and families better appreciate its unique role in fetal medicine.

Genetic and Chromosomal Analysis

Cordocentesis is especially valuable for rapid karyotyping in fetuses at risk for chromosomal abnormalities. When ultrasound detects structural anomalies or severe intrauterine growth restriction (IUGR), cordocentesis can quickly provide results that guide critical decisions. Compared to amniocentesis, cordocentesis can deliver results faster, which is crucial if a late pregnancy diagnosis is needed 1 2 4.

Diagnosis and Management of Fetal Anemia

In pregnancies complicated by maternal-fetal blood group incompatibility (isoimmunization), there is risk of fetal anemia. Cordocentesis allows direct measurement of fetal hematocrit and hemoglobin, helping to assess the severity of anemia and guide the timing of intrauterine transfusions if needed 4.

Detection of Fetal Infections

Some infections, such as those in the TORCH group (toxoplasmosis, rubella, cytomegalovirus, herpes, and others), can be diagnosed by analyzing fetal blood for evidence of infection. Cordocentesis provides a direct route for this, particularly when suspicion is high or other tests are inconclusive 4.

Assessment of Metabolic and Physiological Disorders

Cordocentesis can be used to diagnose or monitor various fetal physiological conditions, such as acid-base status in suspected intrauterine starvation or other metabolic disorders. In rare cases, it is also used for therapeutic interventions, such as intrauterine transfusions or administering medications directly to the fetus 4.

Cordocentesis Test Details

When undergoing cordocentesis, patients may have questions about how the test is performed, what techniques are used, and what risks are involved. Understanding these details can help demystify the experience and set realistic expectations for both the procedure and recovery.

Preparation and Technique

Cordocentesis is performed under continuous ultrasound guidance to visualize the fetus, placenta, and umbilical cord. The mother’s abdomen is cleaned and prepared aseptically. A fine needle (typically 22-25 gauge) is then inserted through the maternal abdomen and uterine wall into the umbilical cord, most commonly at its placental insertion point, though sometimes a free-floating loop or the fetal origin of the cord is targeted for optimal access 1 3 6.

Techniques Used

• Freehand Technique: The clinician manually guides the needle using ultrasound imaging 1 3.
• Needle Guide Technique: A fixed device helps position the needle, which may reduce fetal loss rates 6.
• Combined Approach: Some centers use a needle guide to bring the needle close to the cord, then switch to freehand for actual puncture, aiming to combine precision and flexibility 6.

Needle Selection

Recent studies suggest that using a 25-gauge needle is advantageous, as it minimizes blood leakage and may reduce complications, although it does take longer to draw blood. Importantly, it does not increase the risk of hemolysis or platelet activation in the sample 5.

Sampling Sites

• Placental Cord Origin: Most frequently targeted due to easier access and stability 3 6.
• Free-Floating Loop: Chosen when placental insertion is not accessible 3 6.
• Fetal Cord Origin: Less commonly used, but sometimes necessary 3 6.

Success Rates and Procedure Duration

• Over 90% of procedures are successful on the first or second attempt, with an average sampling time of about 10 minutes. Success rates improve with operator experience 1 3 6.

Complications and Safety

Cordocentesis is generally safe in experienced hands, but as with any invasive procedure, there are risks:

• Bleeding at Puncture Site: Usually minor and transient, occurring in up to 20% of cases 1 3.
• Fetal Bradycardia: Temporary slowing of the fetal heart rate occurs in a small percentage of cases (3-4%) and usually resolves on its own 1 2 6.
• Infection/Chorioamnionitis: Extremely rare 1 3.
• Cord Hematoma: Rare but possible 1 4.
• Fetal Loss: Procedure-related fetal loss rates are reported between 0.9% and 1%, with total fetal loss rates (including all causes) up to 3% 1 6.
• Other Obstetric Risks: Complications such as preterm labor are comparable to those in the general population undergoing other invasive prenatal procedures 1.

Cordocentesis Test Results & Follow-Up

Results from cordocentesis provide rapid, highly specific information about the health of the fetus. These findings guide next steps in care, whether they involve further monitoring, intervention, or difficult decision-making.

Understanding the Results

Cordocentesis test results are typically available within a few days, especially for rapid karyotyping and genetic testing. The findings are interpreted alongside other clinical and ultrasound information to create a comprehensive picture of fetal health.

Genetic and Chromosomal Results

• Rapid Karyotyping: Cordocentesis can quickly determine if a fetus has a chromosomal disorder, such as Down syndrome or trisomy 18. This is especially important in pregnancies with structural anomalies or severe IUGR, as there is a high association between multiple fetal anomalies and abnormal chromosomes 2.
• Impact: Abnormal results may lead to further genetic counseling and influence decisions regarding pregnancy management 1 2 4.

Hematologic Results

• Fetal Anemia: Direct measurement of fetal blood allows precise diagnosis of anemia, especially due to isoimmunization. If severe anemia is detected, intrauterine transfusion can be planned 1 4.
• Other Blood Disorders: Cordocentesis can diagnose hemoglobinopathies or other blood cell disorders 1 4.

Infection Detection

• TORCH Infections: Positive markers for infections such as cytomegalovirus or toxoplasmosis can be directly detected in fetal blood, enabling timely intervention 4.

Physiological and Metabolic Status

• Acid-Base Balance: In cases of suspected fetal distress or starvation, cordocentesis can provide critical information to guide therapy or delivery planning 4.

Follow-Up and Next Steps

The course of action after cordocentesis depends entirely on the results:

• Normal Findings: Usually, no further intervention is needed; routine prenatal care continues.
• Abnormal Findings:
  • Genetic Disorders: May prompt additional testing, genetic counseling, or consideration of pregnancy options.
  • Fetal Anemia: Immediate intrauterine transfusion or close monitoring may be needed 1 4.
  • Infection: Initiation of maternal or fetal therapy, or preparation for specialized neonatal care 4.
  • Severe Anomalies: Multidisciplinary counseling and planning for delivery or palliative care may be warranted 2.

Parents are typically offered follow-up appointments to review results, discuss implications, and plan next steps in collaboration with a multidisciplinary team.

Conclusion

Cordocentesis is a powerful diagnostic and, in some cases, therapeutic tool in modern prenatal medicine. While it is an invasive procedure with some risks, its ability to provide rapid, direct information about fetal health is unmatched in certain clinical scenarios. For families facing complex prenatal diagnoses, cordocentesis can offer clarity, guide interventions, and support informed decisions.

Key Points Summary:

• Cordocentesis is used primarily for rapid genetic testing, diagnosis of fetal anemia, detection of infections, and assessment of metabolic or physiological disorders 1 2 4.
• The procedure typically involves ultrasound-guided needle insertion into the umbilical cord, most often at the placental insertion, using a 22-25 gauge needle; the 25-gauge needle may reduce bleeding risk 1 3 5 6.
• Overall, cordocentesis is safe in experienced hands, with a procedure-related fetal loss rate of about 1% 1 3 6.
• Results provide direct, actionable information that shapes prenatal care, including therapy for anemia, management of infections, and decision-making in the case of chromosomal abnormalities 1 2 4.
• Families receive comprehensive follow-up and counseling tailored to the test results and the needs of the pregnancy.

Cordocentesis remains a valuable option in the prenatal diagnostic toolkit, offering answers and hope in challenging situations.