The effect of uterine contractions on fetal oxygen saturation

Abstract

Objective To find out what happens to fetal arteriolar oxygen saturation during a uterine contraction. Design Prospective observational study. Setting Labour ward, St James's University Hospital, Leeds. Subjects Eighteen women in normal labour monitored with a fetal scalp surface pulse oximetry sensor, an intrauterine pressure catheter, and a head to cervix force transducer. Methods The effect of intrauterine pressure and head to cervix force on fetal arteriolar oxygen saturation was examined using time series analysis and a regression model of 159 contractions. Outcome measure Fetal oxygen saturation during a contraction. Results The average oxygen saturation drops after a contraction. The greatest drop in oxygen saturation is reached 92 s after the peak of a contraction and takes approximately 1 min 30 s to recover (P= 0.036). Conclusion Uterine contractions during normal labour affect fetal oxygen saturation.

History of Fetal Diagnosis and Therapy: Children’s Hospital of Philadelphia Experience

“…The EXIT procedure is significantly different from previous reports of intrapartum laryngoscopy or bronchoscopy in which the fetus was delivered either by traditional cesarean section or vaginal delivery, and the cord was not clamped [74,76]. In these cases there was no attempt to prevent uterine contraction and the fetus was often removed from the uterus, resulting in uterine contraction, placental separation, and cessation of uteroplacental gas exchange [80].…”

Acute centralization of blood flow in compromised human fetuses evoked by uterine contractions

“…These and our results suggest that in both healthy and moderately compromised fetuses at term, once labor has started there are no large oscillatory changes of MCA flow resistance related to the contraction pattern, at least not in the early stages of labor. It takes approximately 2 minutes for the oxygen saturation to fully recover after a contraction 20 and in fetal sheep exposed to acute short-lasting hypoxia it takes up to 5 minutes before the cerebral vascular flow resistance has returned to the baseline level. 24 Hypoxia and hypercapnia are potent and rapid stimuli for cerebral vasodilatation 25 , and with repetitive uterine contractions it is likely that carbon dioxide will accumulate in fetal blood and the oxygen supply will remain at suboptimal levels also during a substantial time of the uterine relaxations.…”

“…20 During the OCT, an already imminently compromised fetus with a restricted oxygen reserve may have difficulties to cope with this hypoxemia.…”

Management of antenatally detected fetal airway obstruction

“…Complete removal of the baby from the uterus allows the uterus to contract sooner, impairing utero-placental gas exchange [18] Access is more uncomfortable for the endoscopist Maternal-fetal circulation persist for an average of only 5 min after delivery (occasionally up to 20 min [4])…”