A cordocentesis can be performed after how many weeks' gestation?

Cordocentesis, also known as percutaneous umbilical blood sampling (PUBS), is a procedure used to obtain a sample of the fetus's blood for diagnostic purposes. This procedure is typically performed during the second trimester and is generally safe after a certain level of fetal development.

The correct answer is that cordocentesis can be performed after 18 weeks of gestation. This timing is crucial because it ensures that the fetus is adequately developed for the procedure, which requires accessing the umbilical cord. By approximately 18 weeks, the umbilical cord is usually sufficiently formed, allowing for easier access to fetal blood without higher risks for complications.

Performing the procedure before 18 weeks might pose increased risks, as the umbilical cord and blood vessels may not be fully developed or may be harder to locate, potentially compromising both the effectiveness of the procedure and the safety of the fetus.

Overall, the timing of 18 weeks is considered optimal for conducting cordocentesis to ensure reliable results while maintaining maternal and fetal safety.