The effects of controlled hyperbarism on pregnant women and fetal development are uncertain.

In eastern Europe, scientists using relatively low pressures but repeatedly and for long periods of time have reported no particular problems with it. One study suggests that while in a hyperbaric atmosphere, the fetus changes its' circulatory flow in the direction of neonatal flow patterns (with narrowed or closed ductus arteriosus and foramen ovale). Upon return to normal barostatus, the flow again reverses to the normal fetal flow pattern. Whether this change poses any long-term problems for the fetus is unknown.

Based on these concerns, it is inadvisable to allow any pregnant woman to dive or enter a hyperbaric chamber unless strongly indicated for medical reasons. If an accident occurs in which it would be desirable to place the pregnant woman in a hyperbaric chamber, the risks to the fetus (mainly theoretical) must be balanced against the risks to the mother of not undergoing hyperbaric treatment.

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Should hyperbaric oxygen be used to treat the pregnant patient for acute carbon monoxide poisoning? A case report and literature review

K. B. Van Hoesen, E. M. Camporesi, R. E. Moon, M. L. Hage and C. A. Piantadosi
Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710.

Carbon monoxide (CO) is the leading cause of death due to poisoning. Although uncommon, CO poisoning does occur during pregnancy and can result in fetal mortality and neurological malformations in fetuses who survive to term. Uncertainty arises regarding the use of hyperbaric oxygen (HBO) as a treatment for the pregnant patient because of possible adverse effects on the fetus that could be induced by oxygen at high partial pressures. While the dangers of hyperoxia to the fetus have been demonstrated in animal models, careful review of animal studies and human clinical experience indicates that the short duration of hyperoxic exposure attained during HBO therapy for CO poisoning can be tolerated by the fetus in all stages of pregnancy and reduces the risk of death or deformity to the mother and fetus. A case is presented of acute CO poisoning during pregnancy that was successfully treated with HBO. Recommendations are suggested for the use of HBO during pregnancy.

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A Case Report
On 26 December 1966, a 22 year-old primipara in the 37th week was
admitted to a maternity hospital for observation because of a minor
antepartum haemorrhage. ....while in bed at 6.50 p.m. on 16th January 1967, she
complained of pins and needles in her left limb and abruptly became unconscious
and cyanosed with sterorous respiration. Because of the marginal nature of the
improvement which had taken place in the patient's condition with 100% oxygen
at normal pressure, and because of the onset now of foetal distress (the foetal
heart rate  had risen to approximately 200 per minute and was irregular),
it was decided to assess the effect of oxygen administration at 2
atmospheres absolute. Before compression started however, the patient began to
have generalized convulsions, which became continuous in minutes, and her
general condition deteriorated until death was thought to be imminent.
Following compression to 2 atmospheres absolute, breathing oxygen,
there was a marked improvement in the patient's condition: the blood
pressure rose to 100/70 mm Hg and the periphery became warm and pink.
The foetal heart rate, which had been 220 and irregular immediately
before compression, fell to 165 and became regular. Caesarian section
was now performed  (Professor I. Donald, University Department of
Obstetrics and Gynaecology), and proceeded remarkably smoothly, though
it was noted that the uterus remained slightly cyanosed in spite of
the high maternal arterial oxygen tension. A normal live female child
was born with an Apgar score of  9.

Ledingham et al. Fatal  Brain  Damage  Associated  with  Cardiomyopathy
of  Pregnancy with Notes on Caesarian Section in a Hyperbaric Chamber
Brit. Med. J., 1968,4,285-287

PREGNANCY AND HBOT
Chapter 17 of the HBOT MANUAL
PAGE UNDER CONSTRUCTION
Carbon monoxide poisoning: pregnancy: hyperbaric oxygen was probably safe.

HBO in the treatment of intrauterine growth retardation