PUBS provides a means of rapid chromosome analysis and is useful when information cannot be obtained through amniocentesis, chorionic villus sampling, or ultrasound (or if the results of these tests were inconclusive); this test carries a significant risk of complication and is typically reserved for pregnancies determined to be at high risk for genetic defect.

[3] PUBS is a type of fetal blood sampling which was originally developed to determine the presence of hereditary abnormalities.

recognised that umbilical cord blood gas analysis can give an indication of preceding fetal hypoxic stress.

[5] It has since become widely accepted that umbilical cord blood gas analysis can provide important information about the past, present and possibly the future condition of the infant.

The first documented use of PUBS came in 1983 by Daffos and colleagues who sampled blood from an umbilical vein with a needle and monitored its maneuvers with an ultrasound.

PUBS has been predominantly replaced by Fluorescence in situ hybridization (FISH) which is a more detailed investigation of chromosomal abnormalities.

[10] A 20 or 22 gauge spinal needle is typically used in PUBS and may be prepared with an anticoagulant, which helps to reduce the risk of clot formation.

If the bleeding is severe, immediate delivery is an option as long as the fetus is old enough to survive, or fetal blood volume restoration may be considered.

[9] The benefits of this alternative, compared to PUBS, are that chances of contamination of the fetal blood are very low, the risk of fetomaternal hemorrhage are reduced, the risk of bleeding from the sampling site is reduced, and access to the sampling site is easy regardless of the position of the placenta.

Umbilical cord blood gas analysis may assist with clinical management and excludes the diagnosis of birth asphyxia in approximately 80% of depressed newborns at term.

For pregnancies in which genetic abnormalities may be present, PUBS can be used to construct a karyotype, usually within 48 hours, and detect irregular chromosomal patterns.

[2] Karyotypes are able to confirm or detect monosomies, trisomies, or missing portions of chromosomes to give a detailed picture of the severity of the genetic defect as well as predicting developmental future.

PUBS is also indicated in the cases of twins with accumulation of amniotic fluid and substantially different growth rates (at least 10%), if the fetus is expected to be breaking down red blood cells improperly, and in the alleviation of hydrops fetalis, a build-up of fluid in at least 2 parts of the fetus.

[28] Suspicion of fetal infections, such as rubella and toxoplasmosis, as well as the need to supply medicine or blood transfusions to the fetus are indications for the use of PUBS.

[2] Due to its invasive nature, the contraindications of PUBS, reasons to not undergo the procedure, must be taken into account in order to ensure the safety of the fetus and the mother.

PUBS should not be performed in mothers testing positive for the human immunodeficiency virus (HIV) due to increased risk of fetal contraction.

[30] A documented case of puncturing a single umbilical artery during PUBS resulted in a decrease in the heart rate of the fetus with irregular improvement;[30] however, it is difficult to conclude that these symptoms were solely the result of the punctured umbilical artery because these fetuses often have preexisting defects and abnormalities.