Scuba diving exposes the body to profound changes in pressure, which affects how gases are absorbed and released by tissues. For the developing fetus, these physiological changes create a high-stakes environment with unique and poorly understood risks. The safety of a dive must be measured by the potential impact on the child she is carrying. The medical consensus on this activity is clear and forms a definitive barrier to diving during gestation.
The Universal Medical Recommendation
Major professional organizations, including the Divers Alert Network (DAN) and the American College of Obstetricians and Gynecologists (ACOG), unanimously advise against scuba diving during any stage of pregnancy. This recommendation is rooted in the ethical inability to conduct human trials on pregnant women, forcing risk assessment to rely on animal studies and limited retrospective surveys. While some surveys of women who dived while pregnant reported birth defect rates within the national average, the data is insufficient to establish safety. Therefore, the prudent course of action is to avoid diving entirely to eliminate potential harm.
The advice to abstain applies from the moment a person begins trying to conceive until after the baby is born. This protective measure is based on the precautionary principle, prioritizing the developing child over the recreational activity.
Fetal Vulnerability to Decompression Sickness
The primary concern regarding diving during pregnancy is Fetal Decompression Sickness (DCS). During descent, increased pressure causes inert gases, mainly nitrogen, to dissolve into the mother’s blood and tissues, a process known as uptake. This dissolved nitrogen readily crosses the placenta, saturating fetal tissues similarly to the mother’s.
The danger arises during ascent, when pressure decreases and the dissolved nitrogen must be released from the tissues as a gas. If the ascent is too rapid, nitrogen forms bubbles in the blood and tissue. In a non-pregnant adult, the lungs are effective filters, trapping these venous gas bubbles before they can enter the arterial circulation and cause damage.
The fetal circulatory system, however, is designed to bypass the undeveloped lungs. This bypass occurs through two structures: the ductus arteriosus and the foramen ovale, a flap-like opening between the upper chambers of the heart. The foramen ovale is a concerning mechanism because it allows venous blood, potentially laden with nitrogen bubbles, to shunt directly from the right to the left side of the heart.
This shunting means the fetus lacks the mother’s pulmonary filtration system, allowing bubbles to enter the systemic arterial circulation. These arterialized bubbles can then travel to the fetal brain and other vital organs, potentially causing arterial gas embolism. Animal studies have shown that the fetus can develop bubbles and signs of DCS even when the mother remains symptom-free. Potential complications include developmental abnormalities, low birth weight, and fetal death, underscoring the heightened susceptibility of the developing circulation to decompression stress.
Non-Decompression Risks of Diving
Several risks associated with the diving environment are heightened during pregnancy, beyond the unique threat of Fetal DCS. The physical exertion involved in handling heavy scuba gear, such as carrying tanks and maneuvering in the water, can be problematic. This strain increases the likelihood of injury and could potentially cause uterine contractions or premature labor.
Physiological changes in the pregnant body also complicate diving safety. Swelling of the mucous membranes, common during pregnancy, makes equalizing pressure in the ears and sinuses more difficult, increasing the risk of barotrauma. Morning sickness and general nausea can be aggravated by boat motion, leading to discomfort and aspiration risks.
The pregnant body’s thermoregulation is altered, making the mother susceptible to overheating or hypothermia. Furthermore, breathing compressed air introduces additional, poorly characterized risks due to higher partial pressures of oxygen and nitrogen. The developing fetus’s response to hyperbaric oxygen exposure or nitrogen narcosis is unknown and cannot be safely tested.
Safe Activities for Pregnant Divers
For divers seeking to maintain their connection to the water, numerous low-impact aquatic activities offer safe alternatives during pregnancy. These activities allow for cardiovascular fitness without the risks associated with pressure changes or overheating from land-based exercise.
Recommended Activities
- Swimming is highly recommended as the buoyancy of the water relieves stress on joints and muscles.
- Water aerobics provides an excellent way to maintain cardiovascular fitness.
- Prenatal swimming classes offer structured, low-impact exercise.
- Snorkeling is a safe surface activity, provided precautions are taken, such as using a snorkel vest for enhanced buoyancy.