A double-blind randomised controlled trial of continuous oxygen therapy for compromised fetuses

To investigate the effect of chronic oxygen therapy in fetuses with absent end diastolic flow in the umbilical artery assessed by doppler analysis at 24-30 weeks of gestation.

A double-blind, randomised control trial was performed with patients blindly allocated to receive humidified oxygen or humidified air.

A tertiary referral hospital in South Africa.

Thirty-two women who presented between 24 and 30 weeks of gestation with a confirmed finding of absent end diastolic flow in the umbilical artery.

After randomisation patients were allocated to receive a 40% mixture of humidified oxygen or humidified air from uniform coloured gas cylinders which were marked either 'a' or 'b' All women received betamethasone from 27 weeks of gestation on a weekly basis. Cardiotocographs were used from 28 weeks of gestation; after 28 weeks of gestation an amniocentesis was considered to confirm fetal maturity. Women were expected to breath the allocated gas continuously apart from meals and visits to the toilet.

Survival of the fetus was the main outcome measure with secondary outcome measures documenting improvement in the fetal condition in utero.

There were 16 women randomised to receive oxygen and 16 to receive air. There were nine survivors in the oxygen group (56.3%) and six in the air group (37.5%) (relative risk 1.5, 95% confidence interval 0.7-3.2). There was a nonsignificant increase in mean birthweight in the oxygen group (858.3 grammes vs 774.4 grammes) and a nonsignificant increase in mean duration of treatment in the oxygen group (12.8 days vs 10.4 days).

This study did not demonstrate that chronic oxygen therapy provides any benefits to compromised fetuses between 24 and 30 weeks of gestation. Larger studies with sufficient power are necessary to assess whether oxygen therapy can reduce perinatal mortality by a clinically useful amount in this group of patients.