For many women, finding out that they are going to become a mother is one of life's most joyous occasions, however after the realisation sinks in that it will mean 9 months ( or more) of no diving the question is often asked; what risks does diving pose to a developing baby? Most divers can recall from their Open Water training that diving isn't recommended during pregnancy but there is very limited research available to explain the risks further. So here at Girls that Scuba, which is the largest female scuba community online, we wanted to dig a little deeper to find out exactly why you shouldn't scuba dive during pregnancy.
*Please note, information is based on recommendations from D.A.N and if you need more insight please give them a call or email.
For ethical reasons, there haven't really been any experiments conducted on humans and surveys have tended to be somewhat inconclusive. Surveys have weaknesses and are not as easily controlled as laboratory research and in some cases can be biased. A survey of divers who had recently given birth included 69 women who had not dived, and 109 women who had. The non-diving group reported no birth defects, while the divers reported defects at an incidence of 5.5%, a rate of occurrence that is normal for the national population. It is worth noting that diving could not conclusively be held responsible for the issues, which could have been caused by any number of unrelated factors. The small sample size makes these results difficult to determine and while surveys can establish correlations, they cannot confirm a relationship between two factors.
Hyperbaric Chamber Animal Studies
We expose ourselves to hyperbaric oxygen (oxygen that is concentrated by pressure) during almost all dives. If you've taken your Enriched Air Diving specialty you'll know that the safe limit for the partial pressure of oxygen (PO2) is accepted as 1.4 bar, with a contingency of 1.6 bar.
Hyperbaric chambers which simulate the increased pressure of diving (and are often used to treat decompression sickness) have been used to test the effects of diving on different species of animal, the results of which can be applied to humans. Exposure to hyperbaric oxygen has shown a range of developmental abnormalities including low birth weights, fetal abortion, bubbles in the amniotic fluid, premature delivery, abnormal skull development, malformed limbs, abnormal development of the heart, changes in the fetal circulation, limb weakness and blindness.
A study of rats exposed to hyperbaric oxygen during the first trimester found no significant differences between offspring for mothers that had "dived" and those that hadn't. The rats were exposed to a PO2 of 1.3 bar for 70 minutes (if the rats were breathing normal air at 21% oxygen, this would be equivalent to a 52m dive)*
*1.3 bar PO2 / .21 (21% oxygen) = 6.1905 bar water pressure = 51.905m depth.
Hamsters were used to test the effect of decompression sickness during the third trimester, mothers who experienced DCS without treatment bore offspring with severe limb and skull abnormalities. Pregnant hamsters that had DCS and were treated in a hyperbaric chamber also bore offspring with defects but with less frequency than the untreated group. Neither group reported noticeable differences in anatomical development between offspring from the non-diving control group and the group that dived without developing signs of DCS.
Sheep were also subjected to experiments as the placenta is very similar to the human placenta. When these sheep did decompression "dives" (past the no stop limits of recreational diving), there were instances where the fetus formed bubbles when the mother showed no symptoms of DCS. When the mothers did show signs of DCS the fetuses demonstrated a more dramatic evidence of affliction. Some sheep that were dived late in their pregnancy showed offspring with limb weakness, heart abnormalities and spinal defects attributed to DCS when the mother was symptom free.
Fully functional lungs are extremely effective in filtering bubbles from circulation. As the fetus receives blood and exchanges gas through the placenta by bypassing its own lungs, there is no pulmonary filtration within the fetus. This would increase the risk of arterial gas embolism as bubbles would be able to reach the brain, spine and other vital organs.
Further to the effects of an increased partial pressure of oxygen and the risk of DCS posed to a growing baby, there are also practical considerations for the mother while diving during pregnancy. Pregnancy will cause swelling of the mucous membranes in the sinuses and could make equalising more difficult. Nausea and morning sickness experienced during the first trimester may be aggravated by sea sickness. A growing bump could pose problems in finding correctly fitting suits, BCDs, weight belts etc and in addition to the hazards inherent in poorly fitted gear, diving may become too uncomfortable to enjoy (I know a heavy weight belt often gives back ache at the best of times!).
No need to stay out of the water entirely
While diving may be off the list of activities while you're carrying, snorkelling is definitely on the agenda. Being in the water will help alleviate aches, pains, swollen joints and water retention and the coolness of the water may provide some relief for those hot sweats. It is also a very beneficial form of low impact exercise. Plus if you're happily snorkelling around and still enjoying the marine life from the surface the release of endorphins can only have a positive effect on the development of the baby. Once the baby has been born, following advice from a doctor, most women can return to diving in 4-8 weeks.
After reading the literature on the subject it is clear why there is a debate over the topic. Data is limited and inconsistent and makes drawing conclusions difficult. The overall picture indicates that while the effect may be small, diving during pregnancy does increase the risk to the fetus which could lead to devastating consequences that no mother would want to carry the blame for. The potential risk for self-blame and anguish on the women's part if she thinks that her decision to go diving has resulted in any kind of negative outcome for the pregnancy is not worth the risk.
Anyone who inadvertently dives while pregnant may take solace in the anecdotal evidence from women who have reported repeated diving without complication, and if a case of DCS occurs while unknowingly pregnant, it is clear that emergency hyperbaric oxygen is better for all involved than forgoing treatment. It is worth noting that there are no air spaces inside the womb, amniotic sack or the fetus so there are no equalisation concerns for the baby should a woman dive while pregnant.
The most prudent option and the overwhelming consensus from diving organisations worldwide (and the overarching opinion of GTS members!) is to avoid diving when pregnant. Due to the ethical challenges of conducting more research and the fact that diving is a completely avoidable risk for most women, it is unlikely that further studies will be able to establish the absolute risk in the foreseeable future.
About the Author
After finishing her degree in Environmental Geography, Gemma moved to Asia to chase the dream of getting paid to go dive. Following a season in Cyprus working with the British Army and the Royal Air Force training snipers, pilots, Ghurkas, reservists and everyone in between to dive, she decided to embark on a career in the Royal Navy as a Warfare Officer, with the aim of specialising in Mine Clearance Diving. Follow Gemma on Instagram @divewithgemma