Relationship between the sonographic pattern of intrauterine growth restriction and acid-base status at the time of cordocentesis

Objective: To determine whether there is a difference in acid-base status at the time of cordocentesis between fetuses with symmetric and asymmetric intrauterine growth restriction (IUGR). Study Design: Nonanomalous singleton fetuses with IUGR who underwent fetal blood sampling for rapid karyotype analysis from 1992-1995 were retrospectively identified. Cases with gestational age <24 weeks, abnormal karyotype, or evidence of congenital infection were excluded. Fetuses were divided into two groups based on Head Circumference/ Abdominal Circumference Ratio (HC/AC). The asymmetric-IUGR group had HC/AC ≥95% tile for GA, and the symmetric-IUGR group had HC/AC <95% tile. GA adjusted values of umbilical venous pH, pCO₂, pO₂, HCO3, hemoglobin and reticulocyte count were calculated by subtracting the mean values for GA from the observed and compared between groups. Results: Both symmetric-IUGR (n=7) and asymmetric-IUGR (n=9) had umbilical venous pH and pO₂ levels lower than GA normative values. However, there were no differences between groups for any of the parameters studied. Conclusions: Fetuses with symmetric and asymmetric IUGR due to UPI display a similar degree of acid-base impairment.