Fetal acid-base balance can be assessed in a number of ways:
Umbilical cord blood analysis for evaluation of the newborn's acid-base status immediately after delivery is the most objective way of assessing the fetal metabolic condition at birth [1-3]. This information can also be useful from medical and medicolegal perspectives since it provides insight into intrapartum fetal physiology and, if normal, excludes perinatal asphyxia or hypoxia secondary to the birth process . As an example, only a minority of newborns who have low Apgar scores are acidotic at delivery [4-6], which suggests that the depression is related to factors other than prolonged hypoxia .
Umbilical cord blood pH and gas values assessed immediately after delivery will be reviewed here. Fetal acid-base physiology is discussed elsewhere. (See "Fetal acid-base physiology".) A general review of acid-base balance can also be found separately. (See "Chapter 10A: Acids and bases".)
There is no consensus regarding indications for umbilical cord blood acid-base analysis postdelivery. We feel it is reasonable to perform this test in the following circumstances: