By: Dr.Hossam Nasef

Any pregnant woman who would not take any medication or may even stop drinking coffee in order to protect her baby (fetus) from unknown risk, will still ask “ is diving safe during pregnancy?”
As a matter of fact, human research is quite defective regarding the direct effect of diving on the fetus, being a passive passenger at depth, but most workers investigating DCS and fetal risk agree that the fetus is not at increased risk.

Let's first discuss the effect of diving on the pregnant mother and then return back to the effect on the fetus.

- During pregnancy, there is a change in the distribution of body fluids with increased interstitial fluids and edema (what is sometimes called the third-space fluids).

The body undergoes as well an increase of 5% in deposited fat during pregnancy.
The combination between this third –space fluid and increased fat stores will definitely alter the inert gas intake and off gassing times for a pregnant woman suggesting her being in an increased risk of DCS.

- Physiological fluid retention during pregnancy also causes swelling of the naso-pharynx that will render many diving pregnant women decongestants-dependant (nasal drops and tablets) with the inherited risk of rebound congestion (reversed blocks).

- A third problem might be the increased gastro-intestinal symptoms (in 60% of pregnancies) like nausea, vomiting, heart burn and reflux which will make riding a boat a night mare and also will increase the risk of vomiting into the regulator during diving.

- Another problem is the state of vasodilatation (opening of skin blood vessels) which puts the pregnant diver at risk of hypothermia in cool water, and the state of increase in the basal metabolic rate (excessive heat production) which increases the risk of hyperthermia in case of heavy activity in warm water.

- Add to all this the uncomfortable fit of the diving gear as the weight belt and the wet suit on the expanding belly, as well the getting tighter wet suit on the already swollen hands and feet will interfere with the exchange of gases increasing the risks of limb DCS.

The pregnant diver, especially in the last few months, will also have some problems in her movements carrying and balancing heavy equipment and will always suffer the simplest entries and exits to and from the water.
Effect of diving on the fetus:

- A lot of researchers have investigated the effect of DCS done to pregnant animals on the offspring to pressures between 6.4 – 7.1 ata (54 – 61 meters) which is in excess of depths encountered in sport diving. The results suggested an increase in the rate of fetal deformity when exposure (diving) was done in early pregnancy (first trimester) while exposure in the last trimester denoted an increase in the number of still birth of those animals as a result of lacking of the lung filter of the fetal circulation which makes the bubbles pass directly to the brain and heart. These results are still not applicable to humans so far.

- Another challenge to the diving fetus is the exposure to a hyperbaric oxygen environment simply as the mother goes underwater or more dramatically if the mother will have to be treated from a diving accident in a chamber using oxygen as a breathing gas. Animal studies showed cardiovascular malformations and blindness in delivered babies of pregnant animals who were exposed to hyperbaric oxygen.

- Human data on hyperbaric oxygen and the fetus are very limited, a case was reported to have been treated from CO toxicity while pregnant using hyperbaric oxygen with a 5 weeks later delivery of a normal infant, while a few cases of maternal non-diving related air embolism cases have been treated with hyperbaric oxygen and all fetuses died with no adequate explanation of the definite cause of death!

-Only two surveys have been conducted questioning the outcome of women who dived while pregnant, although no statistical analysis was done, the results suggested higher rates of low birth weight, birth defects, neonatal respiratory difficulties and other problems in the group that continued to dive while pregnant.
- One of the hazards that could harm the fetus underwater is the accidental envenomation of the pregnant mother by a marine animal, undefined fetal toxic effects may follow, and specific antitoxins (if any will exist) will also hold risk.

In view of the elective nature of diving, even though diving during pregnancy does not clearly increase maternal or fetal incidence of DCS or air embolism, the unborn may be at severe risk if a diving accident occurs. Summarizing that has been cited and said, Pregnant women should not dive.