What are the differences between cordocentesis and amniocentesis?

Generally, cordocentesis and amniocentesis are two common prenatal diagnostic techniques. Their main differences lie in aspects such as timing of the procedure, sampling site, technical difficulty, scope of testing, and risk level. A detailed analysis is as follows:

1. Procedure Timing: Amniocentesis is ideally performed between 16 and 22 weeks of gestation, when there is sufficient amniotic fluid and ample space for fetal movement, minimizing the risk of injury to the fetus. Cordocentesis is typically conducted between 20 and 28 weeks, when the umbilical cord has developed sufficiently in thickness, allowing easier and more accurate localization and sampling, thereby reducing procedural errors.

2. Sampling Site: During amniocentesis, under ultrasound guidance, a needle is inserted through the abdominal wall into the amniotic cavity to extract an appropriate amount of amniotic fluid for testing. In cordocentesis, the needle passes through the maternal abdominal and uterine walls and is directly inserted into the fetal umbilical cord to collect a small amount of fetal blood for analysis.

3. Technical Difficulty: Amniocentesis is relatively simpler and quicker to perform due to the larger space of the amniotic cavity and clear visualization of the target. Cordocentesis requires precise avoidance of the fetal body; additionally, the umbilical cord moves with fetal activity, making accurate targeting more challenging and demanding higher technical skill from the operator.

4. Scope of Testing: Both procedures can detect chromosomal abnormalities. However, cordocentesis also allows assessment of fetal anemia, genetic testing, and diagnosis of intrauterine infections. Amniocentesis offers greater advantages in screening for fetal metabolic disorders and provides more comprehensive test results.

5. Risk Level: The risk of miscarriage associated with amniocentesis is approximately 0.5%–1%, with potential complications including amniotic fluid leakage. Cordocentesis involves vascular puncture and carries a slightly higher risk of miscarriage (about 1%–2%), along with possible complications such as umbilical cord bleeding and infection. Close post-procedural monitoring is required.

Each technique has its specific indications. Physicians will comprehensively evaluate factors such as gestational age, maternal health status, and clinical needs to recommend the most suitable diagnostic method. Pregnant women are encouraged to fully discuss these options with their doctors before making a decision.