Oxygen Supplementation in Contraction Stress Testing
Oxygen supplementation should NOT be routinely administered during contraction stress testing (CST) or labor in pregnant women without documented maternal hypoxemia (oxygen saturation <94%). 1
Evidence Against Routine Oxygen Use
The British Thoracic Society explicitly states that oxygen supplementation during intrauterine fetal resuscitation during labor was widespread in the past but there is no evidence of benefit, and there is weak evidence of harm to the fetus if supplemental oxygen is given for long periods during uncomplicated labor. 1
The use of oxygen during labor is only required when there is evidence of maternal hypoxemia (oxygen saturation <94%). 1
When Oxygen IS Indicated During Pregnancy
Oxygen should be administered in the following specific circumstances:
Major maternal complications: Women who suffer from major trauma, sepsis, or acute illness during pregnancy should receive oxygen therapy with a target oxygen saturation of 94–98%, the same as any other seriously ill patient. 1
Acute pregnancy complications: The same 94–98% target range applies to women with hypoxemia due to acute complications such as amniotic fluid embolus, eclampsia, or antepartum/postpartum hemorrhage. 1
Underlying hypoxemic conditions: Women with pre-existing conditions like heart failure should receive supplemental oxygen during labor to achieve oxygen saturation of 94–98%, unless they are at risk of hypercapnic respiratory failure (in which case target 88–92%). 1
Clinical Context of CST
The contraction stress test evaluates fetal well-being by assessing fetal heart rate response to uterine contractions, which temporarily reduce uteroplacental blood flow. 2, 3, 4 The test itself does not create maternal hypoxemia and therefore does not require oxygen supplementation unless the mother has documented hypoxemia from another cause.
Common Pitfall to Avoid
Do not administer oxygen routinely during CST based on outdated practice patterns. The historical use of oxygen during fetal stress testing was not evidence-based and may cause fetal harm during prolonged administration in uncomplicated cases. 1 Only use oxygen when pulse oximetry documents maternal oxygen saturation below 94%. 1