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Cordocentesis Explained Procedure Cordocentesis, also known as Percutaneous Umbilical Blood Sampling (PUBS), is a specialized invasive test that allows direct access to fetal blood. It is usually performed under continuous ultrasound guidance by inserting a fine needle through the mother’s abdomen into the umbilical vein at or near the placental insertion.
A small sample of blood is withdrawn from the fetus, which is then tested in the laboratory to find out any abnormalities in the fetal blood. Sometimes, if the baby needs treatment (like a blood transfusion for anemia), it can be done through the same needle during the procedure. Cordocentesis is typically reserved for the second trimester onward and is usually performed after about 18 weeks’ gestation.
Indications: Why is Cordocentesis Performed?: Cordocentesis Explained Procedure
When your doctor needs accurate access to direct fetal information or direct fetal therapy, PUBS is one of the best techniques. Clinicians not only use cordocentesis (CC) as a diagnostic tool but also for therapeutic purposes.
Diagnostic Purposes:
Cordocentesis is performed to obtain real-time information about the fetus’s blood composition, genetic makeup, oxygen status, immune reactions, and the presence of infections. The following are some diagnostic indications of CC.
Diagnosis of Fetal Severe Anemia
The middle Cerebral Artery (MCA) Doppler technique is a non-invasive ultrasound procedure that measures blood flow in the middle cerebral artery. It helps doctors screen for fetal anemia or hypoxia, which may result from maternal blood cell antibodies or fetal infections.
While MCA Doppler is the standard non-invasive screening tool, cordocentesis is used to confirm the diagnosis and assess severity, especially when intrauterine transfusion (IUT) is being considered.
Genetic Diagnosis
For the diagnosis of many genetic disorders, amniocentesisor chorionic villus sampling (CVS) is preferred. However, when these procedures are inconclusive or rapid results are needed, doctors perform cordocentesis. The blood sample collected by CC is then tested in laboratories for:
- Chromosomal Analysis or Karyotyping to detect chromosomal abnormalities such as Down syndrome, Turner syndrome, etc.
- DNA-based Tests to identify single-gene disorders (e.g., thalassemia, sickle cell disease, hemophilia, Duchenne muscular dystrophy).
- Biochemical & Enzyme Studies to detect metabolic disorders caused by missing or faulty enzymes (e.g., Gaucher disease, Tay-Sachs disease).
Infectious Disease
Cordocentesis allows direct fetal blood PCR testing, particularly valuable for parvovirus B19 infection. However, for infections like cytomegalovirus and toxoplasmosis, amniotic fluid PCR after appropriate timing remains the more reliable approach, while cord blood testing may provide extra information when viremia is suspected.
It can also help assess the immune response of the fetus by measuring IgM antibodies, which indicate active infection.
Acid-Base Status
When we do cordocentesis, we can assess the acid-base status of the baby directly in real time. This helps us to provide information about the metabolic status and oxygen delivery to the fetus. However, this is applied selectively, and interpretation depends on whether arterial or venous blood is sampled and the gestational age of the fetus.
Therapeutic Purposes:
Since PUBS gives direct access to the fetal circulation in real time, doctors can treat the fetus inside the womb in the same procedural setting.
- Intrauterine Blood Transfusion (IUT): It is a life-saving procedure in which the cross-matched and specially prepared blood is transfused into the umbilical veins of the fetus. Severe anemia in the fetus caused by parvovirus B19, thalasemia major, or other diseases is treated by IUT using the cordocentesis technique.
- Intrauterine Platelet Transfusion (IUPT): Cordocentesis is also a useful therapeutic tool in the transfusion of platelets into the fetus with the Fetal Alloimmune Thrombocytopenia, a condition in which the mother’s body destroys the platelets of the fetus. IUPT is reserved for selected urgent cases because it is high-risk.
- Medication Administration: When the maternal administration is ineffective, doctors use the PUBS route to deliver the drugs directly to the fetus’s circulation. This may be considered in rare cases, such as fetal arrhythmias, where direct anti-arrhythmic medication is required.
Contraindications: When is Cordocentesis not safe?
Although cordocentesis is a useful procedure, it comes with some risks in certain conditions. Doctors weigh the benefits vs risks before performing it. Clinicians usually assess the reasons to be absolute or relative to decide whether the procedure should be performed or not.
Absolute Contraindications:
These are the conditions in which your doctor prefers not to do cordocentesis because the risks are clearly higher than any potential benefits. Cordocentesis is contraindicated when:
- The fetus is already dead to avoid any complications for the mother.
- The pregnancy is in the early weeks because the umbilical vessels and cord insertions are small and mobile.
- The pregnancy termination is already planned.
Major guidelines and reviews suggest PUBS should be done after 18 weeks of the gestational period.
Relative Contraindications:
These are the conditions in which, although there is a certain risk of complications related to the cordocentesis, with the strict precautions, the procedure can be performed. The medical team weighs specific clinical needs and may proceed only in highly selected circumstances.
- Placental abnormalities make access to the umbilical veins difficult and risky.
- Maternal infections with high transmission risk, such as HIV, Hepatitis B & C, and active Herpes simplex. Modern practice weighs maternal viral load and urgency with controlled maternal disease and pressing fetal needs; centers may still proceed with precautions. In some centers, cordocentesis may still be considered with antiretroviral prophylaxis and strict precautions if the fetal indication is compelling.
- Maternal bleeding disorders cause the mother to bleed profusely, leading to serious complications if not managed carefully.
- Oligohydramnios is a condition in which there is very little amniotic fluid (the water around the baby in the womb) during pregnancy, which causes the umbilical cord to stick against the uterine wall, making the procedure complicated.
How is Cordocentesis Performed?
CC needs highly skilled operators and a facility that is usually performed in the tertiary centers.
Pre-Procedure Steps: How do I prepare for Cordocentesis?
Before the CC, doctors examine the fetus and its cord carefully under the ultrasound, check the mother’s blood, prevent infections, and prepare blood for the fetus if anemia is suspected.
- Counseling and consent: Your doctor explains the procedure, its benefits, risks, and alternatives to you.
- Ultrasound evaluation: Ultrasound before the procedure helps the doctor to check the fetal viability, position, cord insertion site, and other fluid or fetal abnormalities.
- Infectious precautions: Infectious diseases like HIV, Hepatitis B & C are tested.
- Maternal laboratory Test: Clinicians perform a focused panel of maternal laboratory tests to prepare the blood bank beforehand for a possible transfusion. These tests can be maternal ABO and Rh blood grouping, and an antibody screen.
- Blood-bank preparation: If there is a likelihood of intrauterine blood transfusion (IUT), a specially prepared blood with donor packed red cells that are O-negative or antigen-matched, leukocyte-reduced, irradiated, and warmed before transfusion is kept prepared.
In some cases, prophylactic antibiotics and anti-D immunoglobulin (for Rh-negative mothers) are also given to minimize complications.
Image Credit: freepik.com
These pre-operative preparations lower the risk of complications during the procedure.
During Procedure: What to expect during Cordocentesis?
During the procedure, the mother should lie on her back in a safe position so that the uterus does not press down on the inferior vena cava, the largest vein taking blood back to the heart. Your healthcare professional cleans your abdomen with an antiseptic solution and instills the local anesthesia to numb the area.
Ultrasound Guidance & Site Selection
Under continuous ultrasound guidance, your doctor locates the placenta, umbilical cord, and fetus to decide the site for needle insertion. After locating the placenta-cord-insertion, the site where the umbilical cord joins the placenta, he/she fixes and stabilizes it to minimize the risk of complications.
Image courtesy: “Umbilical Region, the Cord, and the Placenta at Term” (1916) by Thomas Stephen Cullen, public domain. Source: Wikimedia Commons – File:Umbilical_Region,_the_Cord,_and_the_Placenta_at_Term.jpg (https://commons.wikimedia.org/wiki/File:Umbilical_Region,_the_Cord,_and_the_Placenta_at_Term.jpg
Needle Insertion
Once the site is selected, a long, thin, and hollow needle is inserted into the abdominal wall of the uterus of the mother with the help of an ultrasound. Medical experts observe the needle advancement while it passes through the amniotic fluid to the umbilical cord vessels because it is relatively fixed. If, for any reason, the umbilical vein is inaccessible, a free loop or an intrahepatic vein, a liver vein is an alternative for the sampling.
Fetal Blood Sampling
When the needle reaches the umbilical vein, a small amount of about 0.5–2 mL of fetal blood is taken into the special syringes. This blood sample is enough for genetic, hematologic, and infectious disease testing.
Intrauterine Therapy
The main advantage of this procedure is that it also provides instant therapies for some disorders. For example, if the lab test is done at the spot and confirms the fetal anemia, the already specially prepared blood can be transfused into the fetus through the same procedure in the same setting. If needed, intrauterine transfusion or drug delivery can be performed during the same procedure.
Monitoring During the Procedure
Throughout the procedure, the clinicians monitor the fetus’s heart rate with an ultrasound to avoid any complications. When the needle touches the cord, a temporary bradycardia (lower heart rate) may result in the fetus, which usually resolves within a few minutes. However, if the bradycardia is prolonged, certain prompt urgent actions are needed.
Needle Withdrawal & Post-Procedural Care
After the blood collection and IUT, the needle is withdrawn slowly and carefully. The medical team then monitors the mother and fetus for a short period, usually one to two hours, to ensure there are no complications like continuous bleeding, premature contractions of the uterus, or abnormal fetal heart contractions.
A follow-up ultrasound is also done before discharge to observe the baby’s condition and confirm that the procedural site is stable. If the mother is Rh-negative, administer anti-D immunoglobulin after the procedure per local protocols and perform or consider quantitative fetomaternal hemorrhage testing (e.g., Kleihauer or flow cytometry) when indicated, because PUBS can cause fetomaternal bleeding.
Cordocentesis vs. Other Prenatal Diagnostic Procedures
CC, amniocentesis, and chorionic villus sampling (CVS) are all invasive diagnostic procedures that are performed to get the sample from the fetus, but they differ in timing, technique, and purpose. Risk of fetal loss with cordocentesis is estimated at 1–2% in experienced centers, slightly higher than CVS and amniocentesis.
Cordocentesis vs Chorionic Villus Sampling (CVS):
While both CC and CVS are invasive prenatal diagnostic procedures, CC is performed after 18 weeks of pregnancy and involves obtaining fetal blood directly from the umbilical cord, and CVS is performed earlier, typically between 10 and 13 weeks, by sampling placental tissue (chorionic villi)
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| Feature | Cordocentesis (PUBS) | CVS |
|---|---|---|
| Timing | ≥18 weeks (second trimester onward) | 10–11 weeks (first trimester)9Giovannopoulou, E., Tsakiridis, I., Mamopoulos, A., Kalogiannidis, I., Papoulidis, I., Athanasiadis, A., & Dagklis, T. (2022). Invasive Prenatal Diagnostic Testing for Aneuploidies in Singleton Pregnancies: A Comparative Review of Major Guidelines.Medicina,58(10), 1472. https://doi.org/10.3390/medicina58101472 |
| Sample | Fetal blood (umbilical vein) | Placental tissue (chorionic villi) |
| Use | Detects fetal anemia, infection, blood type, chromosomal abnormalities; guides therapy | Detects genetic and chromosomal abnormalities early |
| Therapeutic role | Both diagnostic and therapeutic (e.g., intrauterine transfusion, drug delivery) | Only diagnostic |
| Result speed | Some results within hours (blood tests, PCR) | Genetic results take days to weeks |
| Fetal loss risk | ~1–3%, higher if fetus compromised | ~0.2–1% in expert centers |
| Limitations | Technically demanding; not possible early in pregnancy | Risk of confined placental mosaicism, early sample failure |
Cordocentesis vs Amniocentesis:
Amniocentesis is usually performed between 15 and 20 weeks of pregnancy by sampling amniotic fluid that surrounds the fetus. This fluid contains fetal cells shed from the skin and respiratory tract, as well as biochemical substances.
| Feature | Cordocentesis (PUBS) | Amniocentesis |
|---|---|---|
| Timing | ≥18 weeks (mainly 2nd–3rd trimester) | 15–20 weeks (2nd trimester)10Giovannopoulou, E., Tsakiridis, I., Mamopoulos, A., Kalogiannidis, I., Papoulidis, I., Athanasiadis, A., & Dagklis, T. (2022). Invasive Prenatal Diagnostic Testing for Aneuploidies in Singleton Pregnancies: A Comparative Review of Major Guidelines.Medicina,58(10), 1472. https://doi.org/10.3390/medicina58101472 |
| Sample Collected | Fetal blood from the umbilical vein | Amniotic fluid (with fetal cells and proteins) |
| Primary Uses | Detects fetal anemia, infections, metabolic disorders, chromosomal abnormalities; also guides therapy | Detects chromosomal abnormalities, genetic disorders, and neural tube defects (via AFP levels) |
| Therapeutic Role | Yes. Allows intrauterine transfusion and drug delivery | No. It is diagnostic only |
| Result Speed | Rapid (blood analysis/PCR within hours; karyotype in ~3–7 days) | Karyotype results in ~1–2 weeks; molecular tests faster |
| Fetal Loss Risk | ~1–3%, higher in compromised fetuses | ~0.1–0.3% in expert hands11Odibo AO, Gray DL, Dicke JM, Stamilio DM, Macones GA, Crane JP. Revisiting the fetal loss rate after second-trimester genetic amniocentesis: a single center’s 16-year experience. Obstet Gynecol. 2008 Mar;111(3):589-95. doi: 10.1097/AOG.0b013e318162eb53. PMID: 18310360. |
| Limitations | Technically demanding; performed later in pregnancy | Cannot be done very early; slower diagnostic window |
Advantages of Cordocentesis
Although PUBS carries higher risks than amniocentesis and chronic villus sampling, it has a unique strength in specific clinical situations.
- Direct access to fetal blood: The direct and rapid access to fetal circulation helps doctors to assess the hemoglobin level, WBCs, platelet count, blood gases, and molecular tests for pathogens accurately, which can’t be done with amniotic fluid or placental tissue.
- Diagnostic and therapeutic role: Through the procedure, doctors can also provide life-saving treatments like IUT, platelet transfusion, and medication delivery directly to the fetus.
- High sensitivity for infections: For certain infections like CMV, rubella, toxoplasmosis, and syphilis, cordocentesis is more sensitive than amniocentesis.
- Real-time assessment of fetus: CC helps to assess the real-time fetal wellbeing by providing immediate information about the blood gases and acid-base balance.
Risks and Complications
As the PUBS involves the direct insertion of a needle into the umbilical cord of the fetus, it carries some serious complications and risks.
- Fetal loss: Large studies identified placental penetration, prolonged bleeding from the puncture site, and persistent fetal bradycardia during and after the procedure as the factors that had increased the fetal damage.
- Immediate fetal events: Fetal bradycardia is the common immediate event during the procedure. Most of the bradycardia events are transient and resolve within minutes, but persistent bradycardia increases the chances of fatal loss.
- Bleeding: Bleeding from the puncture site can create a hematoma, a localized blood collection within the umbilical cord that may compress the vessels and may result in fetal compromise.
- Infection risk: Although with the strict sterile protocols, the chances of infection are low, still, the infections that spread from mother to child might be manipulated during PUBS.
- Maternal complications: The mother can also face issues like local pain, bleeding from the needle entry site, infection of the puncture site, and, though very rare, amniotic fluid leakage.
When careful technique and team readiness are applied, the most serious risk, the fatal loss, is much lower in the procedure.
Conclusion
Cordocentesis is a medical procedure in which a small needle is inserted directly into the umbilical vein of the fetus by passing it through the mother’s womb to get the blood sample. This procedure is done for the diagnosis of any genetic or infectious disease, fetal anemia, or other blood disorders, and for checking the overall well-being of the fetus.
CC has the upper hand on the chronic villus sampling and amniocentesis, which is not only used for diagnostic purposes but also as a therapeutic tool to direct transfusion of blood or drugs into the fetus in the same procedure.
References
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[2] Peddi, N. C., Avanthika, C., Vuppalapati, S., Balasubramanian, R., Kaur, J., & N C. D. (2021). A Review of Cordocentesis: Percutaneous Umbilical Cord Blood Sampling.Cureus,13(7), e16423. https://doi.org/10.7759/cureus.16423
[3] Kagan, K. O., Hoopmann, M., Geipel, A., Sonek, J., & Enders, M. (2024). Prenatal parvovirus B19 infection.Archives of Gynecology and Obstetrics,310(5), 2363. https://doi.org/10.1007/s00404-024-07644-6
[4] Pares, S., Arruda Sousa Pacheco, G. H., Rago Lobo, G. A., & Júnior, E. A. (2024). Intrauterine Transfusion for Rhesus Alloimmunization: A Historical Retrospective Cohort from A Single Reference Center in Brazil.Journal of Clinical Medicine,13(5), 1362. https://doi.org/10.3390/jcm13051362
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[9] Giovannopoulou, E., Tsakiridis, I., Mamopoulos, A., Kalogiannidis, I., Papoulidis, I., Athanasiadis, A., & Dagklis, T. (2022). Invasive Prenatal Diagnostic Testing for Aneuploidies in Singleton Pregnancies: A Comparative Review of Major Guidelines.Medicina,58(10), 1472. https://doi.org/10.3390/medicina58101472
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[11] Odibo AO, Gray DL, Dicke JM, Stamilio DM, Macones GA, Crane JP. Revisiting the fetal loss rate after second-trimester genetic amniocentesis: a single center’s 16-year experience. Obstet Gynecol. 2008 Mar;111(3):589-95. doi: 10.1097/AOG.0b013e318162eb53. PMID: 18310360.
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