Scuba diving involves breathing compressed air at depth, which creates a significant physiological challenge due to pressure changes. For a pregnant woman, this activity introduces unique risks affecting both the developing fetus and the mother. Medical and diving safety organizations worldwide advise against all forms of scuba diving during pregnancy. This recommendation is based on theoretical risks, animal studies, and the lack of ethical human research to confirm safety for the unborn child.
The Primary Danger: Fetal Decompression Sickness
The most serious risk of scuba diving during pregnancy is fetal decompression sickness (DCS). When a diver breathes compressed air underwater, nitrogen dissolves into the mother’s tissues and bloodstream. Nitrogen readily crosses the placenta, saturating the fetal blood and tissues.
During ascent, decreasing pressure causes dissolved nitrogen to form tiny gas bubbles (venous gas emboli). In an adult, these bubbles are filtered out by the lungs before entering the arterial circulation. The fetal circulatory system is different because its lungs are not yet functional for breathing.
The fetus possesses specialized shunts, such as the foramen ovale and the ductus arteriosus, that bypass the lungs. These shunts direct blood flow from the right side of the heart to the left side, creating a vulnerability during a dive. If nitrogen bubbles form, these shunts allow them to bypass the lungs’ filtering action and enter the arterial circulation.
This increases the risk of an arterial gas embolism (AGE) in the fetus, even if the mother has no DCS symptoms. An AGE can block blood flow to developing tissues, potentially leading to birth defects or fetal demise. Animal studies on sheep show that a fetus can develop bubbles even when the mother shows no signs of decompression illness.
Maternal Physiological Changes and Diving Risk
Pregnancy causes physiological changes that increase the mother’s risk during a dive. The growing abdomen makes fitting essential equipment (buoyancy compensation device and weight belt) challenging. This change in body shape negatively affects the diver’s balance and trim, potentially increasing the risk of an uncontrolled ascent or injury.
The body’s fluid balance is altered, increasing plasma volume, which could affect nitrogen uptake and elimination. Hormonal changes often cause swelling of mucous membranes, including those lining the sinuses and eustachian tubes. This swelling can make equalizing pressure difficult, leading to a greater risk of painful barotrauma.
The increased likelihood of nausea and vomiting is a serious complication underwater. Vomiting while diving can compromise the regulator and mask, potentially leading to aspiration or panic. Also, the fatigue often experienced during pregnancy can impair a diver’s judgment and reaction time, reducing the margin of safety.
Medical Consensus and Professional Recommendations
The definitive answer from medical and diving communities is that scuba diving is contraindicated throughout pregnancy. Organizations like the American College of Obstetricians and Gynecologists (ACOG) and the Divers Alert Network (DAN) universally advise against it. This consensus is driven by the serious potential for harm to the fetus.
Since it is unethical to conduct controlled experiments on pregnant women, professional recommendations rely on theoretical physiological risk and animal models. In the first trimester, concern focuses on the impact of hyperbaric exposure on organogenesis. During the second and third trimesters, risks include the potential for premature labor and fetal compromise due to pressure changes.
If a pregnant woman develops maternal decompression sickness, standard treatment involves recompression in a hyperbaric chamber with high concentrations of oxygen. This treatment introduces another layer of theoretical risk to the fetus, as high partial pressures of oxygen may negatively affect fetal circulation or vision development. The medical community’s position is unified: the potential consequences outweigh any benefit, making avoidance the only responsible choice.
Distinguishing Safe Water Activities
While scuba diving is advised against, the recommendation applies specifically to activities involving compressed gas and significant pressure changes. Many other water-based activities are safe and beneficial for pregnant women. Activities that take place at or near the water’s surface without compressed gas are generally encouraged.
Swimming and water aerobics are excellent, low-impact exercises that can help alleviate common pregnancy discomforts like swelling and back pain. Snorkeling, which involves breathing air at surface pressure, is also considered safe, provided the woman avoids rough water conditions. Shallow free diving, where breath-holds are brief and depth is minimal, does not expose the body to pressure changes that cause nitrogen saturation.
These alternatives allow pregnant women to enjoy the aquatic environment without the risk of fetal decompression sickness or complications from maternal physiological changes. Avoidance of scuba diving is temporary, and a return to the sport is possible after childbirth, once a physician confirms it is safe.