There is no established safe depth for scuba diving during pregnancy. The American College of Obstetricians and Gynecologists recommends avoiding scuba diving entirely throughout all trimesters because the fetus faces an increased risk of decompression sickness. This isn’t a case where shallow dives get a pass. The concern applies to any dive involving compressed gas at depth.
Why No Depth Is Considered Safe
The core problem is how a fetus handles gas bubbles differently than an adult. When you breathe compressed air underwater, nitrogen dissolves into your blood and tissues under pressure. As you ascend, that nitrogen can form tiny bubbles. In an adult, the lungs act as a filter, trapping most small bubbles before they reach vital organs.
A fetus doesn’t have that protection. Before birth, most blood bypasses the lungs entirely through two natural shunts in the fetal heart. Gas exchange happens through the placenta instead. This means any bubbles that form in fetal blood have no filter. They can travel directly into the fetal brain, heart, or spinal cord, creating what’s called an arterial gas embolism.
Animal studies using pregnant sheep, the closest model researchers have to human diving physiology, found that fetal lambs sometimes developed bubbles even when the mother showed no signs of decompression sickness at all. When the mothers did develop symptoms, the fetuses were hit harder. Researchers could detect fetal distress through cardiac arrhythmias, which in a fetus can be life-threatening. Some offspring of sheep that were dived late in pregnancy showed limb weakness and spinal defects linked to decompression sickness, despite the mother remaining symptom-free.
What the Research Shows in Humans
Human data on this topic is limited, for obvious ethical reasons. You can’t run a controlled trial asking pregnant women to dive at various depths. What exists comes from retrospective surveys of women who happened to dive before realizing they were pregnant or who chose to continue diving.
One study tracked 129 women across 157 pregnancies and over 1,400 dives. The researchers were unable to establish a significant link between diving and fetal abnormalities, but not because diving was proven safe. The women simply didn’t dive frequently enough per pregnancy to generate statistically meaningful data. The sample was too small and the exposure too inconsistent to draw conclusions either way.
Divers Alert Network (DAN), the leading diving safety organization, summarizes the broader literature this way: a range of developmental problems have been associated with hyperbaric exposure in both animal and human data, including low birth weight, premature delivery, abnormal skull and limb development, heart malformations, changes in fetal circulation, and fetal loss. DAN’s position is that even though the overall effect may be small, the potential consequences are severe enough that the only prudent choice is to avoid diving while pregnant. As they put it, most physicians treat diving during pregnancy the same way they’d treat an unproven drug: if there’s no good reason to take it, don’t.
Snorkeling and Breath-Hold Diving
Surface snorkeling, where you float face-down and breathe through a snorkel without submerging, doesn’t involve pressure changes and carries none of the decompression risks of scuba. It’s generally considered a different activity entirely from a diving-safety perspective.
Breath-hold diving (freediving) sits in a gray area. You’re not breathing compressed gas, so nitrogen loading is far less of a concern on short, shallow dives. But repeated deep breath-hold dives can still create pressure-related effects, and the physical exertion, risk of shallow-water blackout, and oxygen deprivation add their own complications during pregnancy. No medical organization has published specific safe depth or time limits for freediving while pregnant, largely because the research simply doesn’t exist.
Pregnancy Changes That Add Risk
Beyond the fetal concerns, pregnancy itself creates conditions that make diving more hazardous for the mother. Swelling of mucous membranes in the sinuses, a common pregnancy symptom, can make equalizing ear pressure difficult or painful. Nausea can intensify underwater discomfort and increase the risk of vomiting into a regulator. Changes in body shape affect how a wetsuit and buoyancy compensator fit, which can compromise buoyancy control and make it harder to manage an emergency ascent.
Equipment that fit well before pregnancy may squeeze the abdomen or restrict breathing. Pregnancy also shifts your center of gravity and reduces your functional lung capacity in later trimesters, both of which matter when you’re managing gear in open water.
If You Dived Before Knowing You Were Pregnant
Many women discover they’re pregnant after having recently dived, sometimes during the very early weeks. The available human data, while limited, is described by researchers as “generally reassuring” for inadvertent early exposure. Medical experts are clear that a dive in early pregnancy before you knew is not considered a reason for pregnancy termination. The risk from occasional early dives appears to be low, though not zero. The recommendation to avoid diving applies going forward once pregnancy is confirmed.
If a Pregnant Diver Needs Emergency Treatment
In the rare event that a pregnant woman develops decompression sickness or an air embolism, hyperbaric oxygen therapy (the standard treatment, delivered in a pressurized chamber) is still considered necessary. Research indicates that hyperbaric treatment at pressures between 1.4 and 3 atmospheres for 30 to 180 minutes has been found safe for pregnant patients. Delaying treatment carries serious risks. One documented case of a pregnant woman with an air embolism who received delayed treatment at 39 hours after the incident resulted in severe neurological deficits and stillbirth. Emergency treatment remains the priority for both mother and fetus.