Pregnancy and Scuba Diving: The Risks and Research

Pregnancy and diving

Pregnancy is an incredible, life-changing experience. It also carries with it a long list of do’s and don’ts. Many of these are common knowledge: we all know that smoking and drinking are ill-advised during pregnancy, for example – but where does diving fit in? Research on the subject is limited, due in large part to the fact that it is unethical to conduct potentially dangerous experiments on expectant mothers. In this article, we take a look at a few of the theoretical risks for Mom and baby, and the evidence that exists to support them.

The Potential Risk to the Baby

Scientists and medical professionals have two main concerns about the effects of scuba diving on an unborn fetus. The first is connected to a fetus’ exposure to hyperbaric oxygen or oxygen that has been concentrated by pressure. It is thought that this kind of exposure has the potential to alter the signals that tell fetal tissues when and how to develop, potentially resulting in a change in how those signals are interpreted. Depending on the stage at which the exposure occurs, this could lead to a range of different issues – including abnormal development of the skull, heart or limbs; limb weakness; premature delivery or even miscarriage.

For this reason, the effects of hyperbaric oxygen exposure would likely be most severe in the first trimester, when the most important developmental changes occur.

The second concern is connected with decompression illness (DCI), which has the potential to affect the fetus throughout pregnancy but is likely to be most dangerous during the third trimester. Foetuses are thought to be at risk of developing DCI even if the mother remains within no-decompression limits. Sometimes, “silent bubbles” form in the bloodstream during a dive. These are safely filtered out by the mother’s lungs; however, fetal blood circulation bypasses the lungs, with gas exchange occurring via the placenta instead. The bubbles remain in the fetus’ system, therefore increasing the risk of a potentially fatal arterial gas embolism.

The Potential Risk to Mom

While the major concerns of diving whilst pregnant relate to the fetus, there are some theories that doing so could negatively affect the mother as well. The natural increase in deposited fat during pregnancy could put Moms at a higher risk of developing DCI. Swollen mucous membranes in the sinuses are another common symptom of pregnancy and could make equalizing difficult – thereby increasing the likelihood of barotrauma. In truth, though, the biggest drawback for pregnant women is the discomfort of diving while nauseous; or in equipment that fits poorly due to their growing abdomen.

The Research

Many of the theories that surround pregnancy and diving are based on scientific conjecture rather than proven fact. Research is limited to surveys completed by women who went diving before realizing they were pregnant, and studies carried out on animals. One survey published in 1980 compared the experiences of 69 women who did not dive whilst pregnant, and 109 women who did. Those that did not dive reported a 0% incidence of birth defects, while the group that had gone diving reported a 5.5% incidence of birth defects. However, it’s important to remember that the latter percentage remains within the normal range for the national population.

It also cannot be proved whether the defects the diving mothers experienced occurred because they had gone diving whilst pregnant, or whether they were the result of unrelated factors.

Tests on pregnant animals exposed to diving-like conditions in a hyperbaric chamber also shed some light on the potential risks of diving while pregnant. For example, a study on pregnant hamsters showed that those with untreated DCI gave birth to offspring with severe limb and skull abnormalities, while those that developed DCI but were treated suffered a lower incidence of birth defects. The same study showed that the hamsters that went “diving” but didn’t develop DCI showed little difference from the control group of non-diving hamsters in terms of the effects on their offspring.

Sheep were chosen as the subject for another study because of the physiological similarities between ovine and human placentae. This study supports the theory that DCI could be a problem for a fetus even when the mother remains unaffected. Some pregnant sheep exhibited no signs of DCI, but bubbles were still detected in the fetus. When the mother did develop DCI, the fetus’ affliction was proportionately more severe. Some of the issues caused as a result of bubbles forming in the fetal tissue included the disruption of the fetal heartbeat, weakened limbs, and spinal defects.

The Bottom Line

The bottom line is that the existing research is both dated and inconclusive. Surveys are often biased, and the difference in anatomy between people and animals means that hyperbaric pressure may not have the same effect on humans as it does on hamsters or sheep. However, the lack of certainty surrounding pregnancy and diving means that the safest course is abstinence. This is an opinion corroborated by the Divers Alert Network (DAN), which recommends ceasing all diving activity until several weeks after delivery.

However, anecdotal evidence suggests that Moms who go diving before realizing they are pregnant have very little reason to worry – the likelihood of an issue occurring, as a result, is small. If you’re concerned, make an appointment for a check-up to put your mind at ease.