Evaluation of placental function using near infrared spectroscopy during fetal growth restriction

Objectives: To investigate whether a near infrared spectroscopy (NIRS) system is useful for evaluation of the placental function in cases of fetal growth restriction (FGR). Methods: Subjects included 282 delivered neonates of appropriate for gestational age (AGA) and 44 small for gestational age (SGA) babies. The measurement of the concentration of oxyhemoglobin (HbO₂) and deoxyhemoglobin (HHb) was conducted using transabdominal NIRS targeting the placenta at around 20 weeks, 30 weeks and after 36 weeks of gestation and calculated tissue oxygen indexes (TOI=HbO₂/total Hb). We correlated between TOIs and causes of FGR. Results: TOIs measured immediately before delivery in the SGA group with severe pre-eclampsia (79.2±3.8 (%±standard deviation (SD); P=0.002)) and placental abnormalities (78.2±3.6; P=0.043) were higher than in the AGA group (74.0±4.5). TOIs in the SGA group with umbilical cord abnormalities were lower (69.7±7.7; P=0.024) than in the AGA group. Conclusion: NIRS might provide information about blood oxygen level of the intervillous space and thus explain the cause of FGR.