Fetal acidosis in prolonged pregnancy cannot be attributed to cord compression alone

Area of Science:

• Perinatal medicine
• Obstetrics
• Fetal physiology

Background:

• Prolonged pregnancy is often linked to umbilical cord issues, but fetal intolerance to labor suggests other factors.
• Existing theories do not fully explain why only some fetuses in prolonged pregnancies develop labor intolerance.

Purpose of the Study:

• To investigate the role of suboptimal placental function in prolonged pregnancies.
• To determine if placental insufficiency contributes to reduced amniotic fluid and fetal intolerance to labor.

Main Methods:

• Prospective collection of biochemical and clinical data from 112 pregnancies exceeding 41 weeks' gestation.
• Blinded analysis of cord blood acid-base status and intrapartum fetal heart rate patterns.
• Assessment of amniotic fluid volume and birth weight.

Main Results:

• High incidence of umbilical cord compression (46.4%), but not consistently predictive of emergent delivery.
• Fetal acidosis was more common with cord compression, but metabolic acidosis was observed in emergently delivered fetuses.
• Lower amniotic fluid volume and diminished birth weight were noted in fetuses delivered due to intolerance to labor.

Conclusions:

• Suboptimal placental function appears to play a direct role in fetal intolerance to labor in selected cases of prolonged pregnancy.
• Findings challenge the sole attribution of fetal heart rate abnormalities in prolonged pregnancies to umbilical cord vulnerability.
• Reduced amniotic fluid and fetal acidosis suggest placental insufficiency as a contributing factor in these cases.