Volume 69, Number 9 OBSTETRICAL AND GYNECOLOGICAL SURVEY Copyright © 2014 by Lippincott Williams & Wilkins

CME REVIEW ARTICLE

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CHIEF EDITOR’S NOTE: This article is part of a series of continuing education activities in this Journal through which a total of 36 AMA PRA Category 1 CreditsTM can be earned in 2014. Instructions for how CME credits can be earned appear on the last page of the Table of Contents.

Diving and Pregnancy: What Do We Really Know? Jacqueline Conger, MD,* and Everett F. Magann, MD† *Resident, PGY-1, and †Professor, Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, AR Exercise during pregnancy has been advocated by many professional organizations to promote fetal heath and maternal well-being. Those same professional organizations do not recommend diving during pregnancy because of the potential adverse outcomes that have been observed in the animal model. In nonpregnant women, diving becomes problematic at depth as the ambient pressure increases and more gases become dissolved in the bloodstream. This can result in oxygen toxicity and nitrogen narcosis. Too rapid an ascent from depth can cause nitrogen emboli that can lodge in joints and tissue, resulting in decompression sickness, known as “the bends.” The best animal model to study the effects of diving on pregnancy is the sheep model. Bubbling has been observed in both ewes and their fetuses, with bubbles more common in the ewes. Repeated decompressions done improperly can lead to fetal death. Information on pregnancy outcomes in humans is more limited, with inconsistent data on diving and birth defects, spontaneous abortions, and stillbirth. Even in the face of overall increased resistance in the maternal or fetal placental circulations, the total placental blood flow is usually maintained, preventing adverse outcomes. It appears that the safest choice during pregnancy is to avoid diving; however, if the woman dove when she did not know she was pregnant, there is usually a normal outcome. If a women insists on diving during pregnancy, she should go to a depth of only 60 ft, and duration of her dive should be half that recommended by Navy dive table times. Target Audience: Obstetricians and gynecologists, family physicians Learning Objectives: After completing this CME activity, physicians should be better able to describe the normal physiologic changes encountered in the descent and ascent from a dive, to counsel patients who are interested in diving.

Exercise during pregnancy in low-risk women has been advocated as promoting the health and wellbeing of the pregnant mother and her unborn child, and recently exercise has been reported as boosting neonatal brain activity.1 Multiple organizations, including the American College of Obstetricians and Gynecologists, the Society of Obstetricians and Gynaecologists of Canada, the Royal College of Obstetricians and Gynaecologists, and the Australian and New All authors and staff in a position to control the content of this CME activity and their spouses/life partners (if any) have disclosed that they have no financial relationships with, or financial interests in, any commercial organizations pertaining to this educational activity. Correspondence requests to: Everett F. Magann, MD, 4301 W Markham St, #518, Little Rock, AR 72205. E-mail: [email protected].

Zealand College of Obstetricians and Gynaecologists, have endorsed exercise in low-risk women and have published guidelines on exercise during pregnancy. All of these groups endorse exercise, including strength training, for low-risk pregnant women.2 Recreational diving has become a popular sport with many women in the reproductive-age group.3 When these women become pregnant, they frequently want to know about the dangers of diving in pregnancy. Can they continue to dive at all during pregnancy? If recreational diving is unsafe, can they modify their diving (decrease diving depth or decreasing the length of time that they dive) and then continue to safely dive during pregnancy? The American College of Obstetricians and Gynecologists,4 the Royal College of Obstetricians and Gynaecologists,5 and the Society of Obstetricians

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and Gynaecologists of Canada6 all caution women to avoid scuba diving during pregnancy because of the potential for decompression sickness, and all 3 organizations cite the same article by Camporesi7 on diving and pregnancy. The purpose of this article was to review what is currently known about the safety of diving during pregnancy considering the normal physiologic changes that occur during pregnancy and what is known from the animal model and discuss the impact of diving on pregnancy and pregnancy outcomes. A search was undertaken using the search engines PubMed and Web of Science and using the search terms “diving” OR “scuba diving” AND “pregnancy” OR “pregnant” OR “fetus” OR “fetal.” No limit was put on the years searched. There were 45 publications identified. The abstracts of all articles were read, and the full article that corresponded to diving and pregnancy or pregnancy outcomes was then reviewed. Finally, the references for all of the articles linking diving and pregnancy outcomes were screened for any additional applicable articles. Of the 45 abstracts identified, 19 of the abstracts were either duplicates or articles published prior to 1960 and were unobtainable. Eighteen articles were added after screening the reference list of each of the articles for additional publications. Of the 44 articles that were read, 18 articles were used as the basis of this review (Fig. 1).

Normal Physiologic Changes That Are Encountered With Diving In order to dive for longer than just a few minutes, people must be able to breathe below the surface of

FIG. 1. Literature search for diving and pregnancy.

the water. This is achieved by breathing compressed air delivered under pressure through a respirator. As one descends, the ambient pressure increases by 1 atmosphere (atm) for every 10 m below the water’s surface. During inhalation, the pressure in the respiratory tract only needs to be slightly less than the ambient pressure in order for gas to be delivered by the respirator. So with increasing depth, the ambient pressure increases, and the inhaled gases are delivered at increased partial pressures. The inhaled gases are dissolved into the bloodstream and tissues, and with increasing partial pressures, more gas becomes dissolved. The most common gas mixture breathed by divers is compressed air, which is primarily nitrogen and oxygen. When increased amounts of oxygen are present in tissues, they are used for normal body metabolism and are not problematic until the partial pressure of the inhaled O2 increases to the point at which it is equivalent to breathing pure O2 at sea level; this increases the risk for oxygen toxicity. The effects of oxygen toxicity include vertigo, nausea, and even seizures, which may result in drowning.8 Nitrogen, on the other hand, is an inert gas and will accumulate in tissues. This can become problematic for a number of reasons. The first is that nitrogen dissolved at too high a concentration can cause nitrogen narcosis, which has effects similar to alcohol intoxication. The second is that during ascent, ambient pressure decreases, allowing nitrogen to decompress out of solution and be released from the tissues back into the vasculature. If excess nitrogen is present in the circulation, bubbles can form. Normally, the adult lung will help to filter these bubbles by allowing diffusion out of the vasculature into the alveoli, where the nitrogen is then exhaled. However, if the nitrogen burden is too great, the lungs’ filtering mechanism can be overcome, and air emboli can lodge in various places throughout the body with wide-ranging consequences. These nitrogen emboli cause a variety of symptoms that collectively are referred to as decompression sickness, or historically, “the bends.” This name, as one might infer, comes from the fact that decompressed gas (nitrogen) is the cause of the illness. The illness can range from fatigue and joint aches and pains, which are the most common manifestations, to pulmonary air embolism, paralysis, seizure, and death. In order to avoid decompression illness (DCI), dive tables exist, outlining depths and maximum times at depth that do not require the diver to ascend more slowly than the rate of 60 ft/min, which is accepted as the maximum rate of ascent to prevent

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Diving and Pregnancy • CME Review Article

the “bends.” When a diver has been at depth longer than suggested in the dive tables, he/she is required to stop periodically during ascent to allow more of the excess nitrogen gas that has decompressed out of the tissues and moved back into the circulation, to diffuse into the alveoli and be exhaled. Stopping periodically at certain depths prevents more nitrogen from decompressing out of the tissues, keeping the burden low and theoretically preventing DCI. When someone uses the term “no-stop dive times,” they refer to dive profiles that do not require the diver to make these stops during ascent. In addition, temperature regulation is of paramount importance to the diver. Diving in cooler waters requires thermal protection in the form of a suit; most commonly a wet suit, although dry suits are used as well. The wet suit helps prevent hypothermia in cold water, which would affect both cognitive and physical functioning and could lead to death if one became unconscious underwater.9 Overheating is also a concern in more tropical climates, so divers must make sure to dress appropriately given the water temperature of their surroundings.

Normal Physiologic Changes During Pregnancy There are a number of maternal physiologic changes that take place during pregnancy. The overall vascular resistance decreases by 25% early in pregnancy to accommodate the increased plasma volume of 50% that peaks at 28 to 32 weeks and remains stable until term. The red blood cell mass increases by 20%, but that is lower than the increased plasma volume, resulting in the physiologic anemia of pregnancy. Cardiac output increases from 30% to 50% (4–6 L). The increased cardiac output is the result of an initial increase in stroke volume and a subsequent increase in heart rate of 15 to 20 beats/min. Profound maternal hypotension can be observed with motionless standing in the first trimester of pregnancy and by compression of the maternal vena cava by the pregnant uterus in the second and third trimesters of pregnancy. Observed pulmonary changes include an increased minute ventilation, alveolar ventilation, and tidal volume. Women breathe deeper in pregnancy but do not increase their respiratory rate. This deeper breathing reduces carbon dioxide, resulting in a compensated respiratory acidosis (pH 7.44), which is compensated for by the elimination of HCO3 by the kidneys. Renal plasma flow increases by 45% and renal vasculature resistance by 25%. All of these changes optimize pregnancy and pregnancy outcomes.

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The Animal Model and What It Tells Us About Diving During Pregnancy Animal studies are frequently used to determine the effects of diving on humans. The assessment of the animal placenta that most closely resembles the human placenta is very important because the placenta facilitates gas exchange.10 Many animal models have been used including dogs, rats, hamsters, and sheep. Although dog and rat placentas are similar to human placentas in the number and origin of layers separating fetal and maternal blood, their gas exchange is flow limited, and diffusion is not limited by the membranes themselves. The sheep model appears to be the closest to the human.10,11 Placental blood flow is thought to be more important in gas exchange. Both the sheep and human placentas are villous and have concurrent blood flow. Dog and rat placentas are labyrinthine and thought to have countercurrent blood flow, which allows for faster diffusion and clearing of gases.10 This might explain why the results of studies performed on pregnant dogs and rats do not show much effect in the way of bubble formation or DCI in the exposed fetuses.12,13 For these reasons, the sheep model appears to be the closest to the human and is used to determine diving effects on humans. In 1978, Fife et al14 used 7 female sheep within 3 weeks of parturition and placed ultrasonic Doppler transducers around both the umbilical arteries and maternal jugular veins in order to detect bubble formation. Pregnant ewes were exposed to 17 different simulated dives in a hyperbaric chamber. After each dive, the animals were monitored, and if bubbles were detected in either the maternal or fetal circulation, treatment was initiated in a hyperbaric chamber, which allowed the animals to be recompressed and then decompressed more slowly to prevent further DCI. The investigators found that in all of the cases of fetal DCI, the mothers had no circulating bubbles. An autopsy was performed on 1 untreated mother and fetus approximately 30 minutes after dive, and no bubbles were found in the maternal circulation, but the fetus had massive gas emboli and foam in the ventricles of the heart. From the data reported, it appears that few bubbles were even detected at 60 ft of sea water (fsw) (33 fsw is equal to 1 atm), which was historically recognized as a safe depth for pregnant human divers.22 The validity of these studies has been questioned because it is suspected that even though the vessels were not instrumented it is possible that the transducers around the vessels caused constriction and therefore turbulence of flow that produced bubbles.14 In addition, Powell and Smith15

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posited that 2 major limitations of this study were that the maternal jugular vein is a poor indicator of total body bubble status (the precordium is a more appropriate site) and that Doppler probes likely caused artifacts. Other investigators16–18 have speculated that although fetal vessels were not entered, high-frequency sound waves used by the Doppler may have caused bubble formation. This study suggests the fetus is more susceptible to bubble formation than the pregnant ewe, but other investigators have speculated that the bubble formation observed was the results of the Doppler assessment. In 1980, Stock et al16 evaluated 1 group of pregnant sheep that underwent catheterization for blood flow monitoring, and another group that did not. In the catheterized group, maternal hindlimb arteries and veins and right carotid arteries were catheterized. Among the surgical group, maternal arterial and fetal venous pH remained normal after the dives. Blood flow was assessed using radiotracers injected into both the maternal and fetal circulations. In the postdive period, there was a decrease in maternal placental blood flow with an increase in maternal placental vascular resistance. There was also an increase in maternal arterial pressure but without a change in maternal renal vascular resistance. No change was observed in the fetal blood pressure, placental vascular resistance, or renal vascular resistance at 5 minutes after dive. A total of 11 fetuses were subjected to simulated dives in a hyperbaric chamber to 100 fsw. Six of these fetuses were surgically catheterized. Five of the 6 died within 20 minutes after dive. The sixth exhibited cardiac arrhythmias, and all were found to have significant intravascular bubbling and cardiac intraventricular foam upon autopsy. None of the 5 uninstrumented fetuses showed obvious bubbling after dive, and on autopsy of 2 of the fetuses, no intravascular bubbles were found. Five fetuses, 3 of which had undergone catheterization, were subjected to simulated 60 fsw dives. Two of the 3 catheterized fetuses died during postdive observation, and the third showed cardiac arrhythmias. All 3 had intravascular bubbling at autopsy. The 2 lambs that had not been catheterized had no intravascular bubbles. The authors hypothesize that the instrumentation of the vessels was likely the source of bubbles observed in the fetal circulations, as the uninstrumented lambs were unaffected. Others have conjectured that given that the autopsies of the unaffected lambs were not performed until 3 hours after birth, the lambs were allowed time to clear any bubbles that might have been present at birth.15 This study suggests a decrease in maternal blood flow and increase in placental resistance in simulated

no-decompression dives, but the bubbling observed in the fetal autopsies was a result of the surgery and monitoring that was carried out rather than the result of the dive. In 1981, Nemiroff et al19 simulated dives in 11 pregnant ewes in late gestation. The ewes were subjected to 1 to 6 dives, which were equivalent to 165 fsw for 20 minutes, for a total of 31 dives.19 Only 12 of 31 dives used noninvasive Doppler monitoring of both the maternal and fetal circulations. No fetal bubbling was detected, but 8 of 12 monitored ewes exhibited intravascular bubbling. None of the ewes or lambs exhibited any of the traditional signs of DCI. All of the ewes, except for one who delivered stillborn twins thought to be due to an abnormal labor, delivered normally developed, healthy lambs. The authors speculate that the absence of bubbling is because the sheep were not instrumented and that fetuses seem more resistant to bubble formation than their mothers. In their 1983 article, Wilson et al14 subjected 2 groups of pregnant ewes (days 49–133 of gestation) to simulated dives equivalent to 165 fsw for 20 minutes at depth. Both groups were decompressed at a rate of 30 ft/min; however, group A was decompressed in stages, making stops at 20 ft for 4 minutes and 10 ft for 15 minutes. Group B did not make any stops during decompression. In group B, 4 of 6 ewes delivered prematurely. In group A, 1 ewe exhibited DCI that improved after treatment. In group B, all of the ewes exhibited these same DCI signs after at least half of the dives. Among the lambs born to group A, only 1 had any abnormalities, a spinal deformity resulting in hindlimb weakness reported to be seen in lambs that had not been stressed during pregnancy, whereas in group B, only 1 of 6 lambs were born alive without abnormalities. Three of the ewes delivered stillborn lambs. Another lamb was born with hindquarter weakness, and the last with respiratory problems that led to death within 2 days of delivery. The authors concluded that sheep fetuses could be affected and sometimes killed by repeated hyperbaric exposures when not properly decompressed. In 1983, Stock et al20 attempted to determine the changes in ovine placental blood flow during the postdive period on 10 ewes of approximately the same gestational age. The ewes were subjected to simulated dives after catheters had been placed in the femoral and the right carotid artery. Dives were to 25 fsw/min and 60 fsw/min, with dive times of 25 minutes from start of descent to start of ascent. Blood flow measurements were obtained from the small intestine, kidneys, placental membranes, brain, heart, and skeletal muscles of the ewes. The results showed that although fetal

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Diving and Pregnancy • CME Review Article

arterial pH (7.37 ± 0.04) did not change throughout the 20 minutes after dive, all of the fetuses exhibited arrhythmias, and 6 of the 10 died within 25 minutes after dive. The first change in fetal blood flow noted was a decrease in blood flow to the brain at 5 minutes followed by arterial hypertension. Decreased blood flow with an increased vascular resistance was observed in the small intestine, kidneys, placental membranes, skeletal muscle, and brain. The heart did not exhibit any change in blood flow or resistance. Overall fetal heart work increased by 46%. There was an increase of resistance in the placenta that occurred, but only after resistance had increased in other organs. Of the 6 placentas evaluated at the cotyledonary level, there was no consistent pattern of change in resistance and blood flow observed. The authors concluded that this experiment again reinforced the notion that instrumenting vessels leads to vascular embolization and disruption of organ blood flow and that the changes in blood flow observed at the cotyledonary level are not sufficient to fully explain the resulting embolizations and end-organ effects observed. In 1985, Powell and Smith15 did an experiment using 2 pregnant ewes and 2 pregnant goats simulating dives to depths of ~160 fsw for 5 to 15 minutes at depth. The investigators observed that gas bubbles were observed in the fetal circulation after decompression even when the mother was asymptomatic; fetal bubbles form after and dissipate before maternal bubbles; fetal cardiac arrhythmias are the first sign of fetal distress, and they are usually simultaneous to a symptomatic presentation in the mother. There are several conclusions that can be drawn from these animal experiments, which were all performed late in gestation. • Instrumentation of vessels leads to intravascular bubbling, even when the vessels are not directly entered, as the transducers that are placed around the vessels can lead to constriction and subsequent turbulent flow that produces bubbles.10,14–16 • Massive bubbling in the fetus often leads to cardiac arrhythmias, and upon autopsy, foam has been seen in the heart chambers.10,15,16,20 • Mothers form bubbles earlier and in larger quantity than do their fetuses. Fetuses also clear bubbles faster than do their mothers.15,19 • The longer the time at depth, the more bubbles are formed.15 • Repeated decompressions, when done improperly, can result in death of the fetus.14 • It is likely that bubbles are present in the circulations of both mothers and fetuses even when they are asymptomatic. It is also likely that the Doppler



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technology and methodology used 5 years later by Powell and Smith allowed for better bubble detection than those employed previously by Stock et al. Fetal arterial and venous pH is unchanged by decompression. It is not possible to make concrete statements as to the changes in placental vascular resistance based on the studies by Stock et al; however, it seems that even in the face of some overall increase in resistance in either the fetal or maternal placental circulation, the total placental blood flow is maintained well enough to prevent adverse effects. Impact of Diving and the Normal Physiologic Changes of Pregnancy

Fife and Fife21 discuss some of the possible changes and limitations a pregnant woman might encounter in attempting to dive. They state that the increased amount of body fat in pregnancy could make DCI worse, as fat absorbs more nitrogen during compression. Also, engorged mucous membranes may inhibit pressure equalization in the middle ears. Later in pregnancy, as the woman grows, it becomes more difficult for the suit and equipment to fit properly. Increased incidence of reflux, nausea, and vomiting also make diving dangerous. Impact of Diving on Pregnancy Outcomes For obvious reasons, it is difficult to do any largescale trials to evaluate the effects of diving on pregnancy outcomes. Most of the data that do exist are from retrospective studies that include self-reported data from questionnaires. In 1980, Bolton22 published the results of 1 such retrospective study. She found that of 109 women who dove while pregnant and 69 who did not, there were no stillbirths or neonatal deaths in either group. The diving group showed a 5.5% rate of birth defects, whereas the nondiving group had none. Of the complications reported from the diving group, there was 1 congenital absence of a hand, 1 baby with multiple hemivertebrae, 1 pyloric stenosis, 1 ventricular septal defect, 1 possible coarctation of the aorta, and 1 hairy birthmark. Four women from the dive group experienced vaginal bleeding during pregnancy. The mothers of the 2 infants with skeletal abnormalities had both made dives more than 100 ft during the first trimester of pregnancy. Although the rate of birth defects in the dive group is significantly greater than that of the nondive group, it is comparable to the population baseline rate. The official recommendation cited

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is to avoid diving, but she suggests that if women still choose to dive, they should only go to a depth of 60 ft and for durations of half Navy dive table times.22 In 1982, a case report was published describing a baby born with arthrogryposis and dysmorphic features whose mother had dove during the 40th to 50th days since last menstrual period. The mother had made ~20 dives during a 2-week period, with 4 of them being at depths of at least 100 ft. The author recommends that the best course of action to prevent birth defects would be to forego diving during pregnancy.23 In 2006, St Leger-Dowse et al24 published on both a retrospective study and a prospective study based on self-reported surveys in the United Kingdom. Of the total number of women studied, 129 women dived during their pregnancies, with a total of 1465 dives and 157 pregnancies. There was 1 stillbirth reported, 16 elective terminations, and 22 spontaneous abortions. The spontaneous abortion rate in the group was the same as the average for the United Kingdom. Twenty percent of women reported some abnormality with either the pregnancy or the pregnancy outcome. The authors found that of the women reporting complications many had engaged in other activities that could have put the pregnancy at risk, such as sky diving and horseback riding. It is also of note that 2 women had elective terminations because of the uncertainty of the effects diving could have had on their pregnancy outcomes. In addition, the authors discuss a possible protective mechanism of bubble filtration through the liver in the fetus, as this has been observed in adult divers.

SUMMARY There are not enough human data available on the effects of diving during pregnancy to make a solid conclusion. It would appear from the studies in pregnant ewes that the fetus is very much at risk of DCI; however, as the different studies often have varying results, it is difficult to definitively answer this question in sheep as well as humans. For this lack of concrete evidence from which to draw conclusions, we again echo the recommendation that the safest choice for mothers and their unborn fetuses is to avoid diving while pregnant or while the possibility of pregnancy exists. However, if a woman does dive during pregnancy, there is no evidence to support recommending termination of the pregnancy, as most women who dove during pregnancy still had normal outcomes.7,24

ACKNOWLEDGMENT The authors thank Donna G. Eastham, BA, for her editing skills. REFERENCES 1. Exercise during pregnancy boost your baby’s brain. Available at: http://abcnews.go.com/blogs/health/2013/11/11/exerciseduring-pregnancy-can-boost-your-babys-brain/. Accessed November 25, 2013 2. de Maio M, Magann EF. Exercise and pregnancy. J Am Acad Orthop Surg. 2009;17:504–514. 3. Popularity of diving. Available at http://wiki.answers.com/Q/ How_popular_is_scuba_diving#. Accessed November 25,2013 4. American College of Obstetricians and Gynecologist. Exercise During Pregnancy and the Postpartum Period. Washington, DC: ACOG Committee Opinion 267; ACOG January 2002 (reaffirmed 2009). 5. Royal College of Obstetricians and Gynaecologists. Exercise in Pregnancy. London, UK: RCOG; 2006; RCOG statement 4. 6. Society of Obstetricians and Gynaecologists of Canada. Exercise in Pregnancy and the Postpartum Period. Ottawa, Ontario, Canada: SOGC/CSEP; 2003; SOGC/CSEP Clinical Practice Guideline 129. 7. Camporesi EM. Diving and pregnancy. Semin Perinatol. 1996; 20:292–302. 8. Strauss RH. Diving Medicine. Am Rev Respir Dis. 1979;119: 1001–1023. 9. Whitaker AJ, Bodiwala GG. Immediate management of diving emergencies. Br J Sports Med. 1982;16:102–106. 10. Fife WP, Simmang C, Kitzman JV. Susceptibility of fetal sheep to acute decompression sickness. Undersea Biomed Res. 1978;5:287–292. 11. Meschia G, Battaglia FC, Bruns PD. Theoretical and Experimental study of transplacental diffusion. J Appl Physiol. 1967;22: 1171–1178. 12. McIver RG. Bends resistance in the fetus. Annual Scientific Meeting. Aerosp Med Assoc; 1968. 13. Chen V. The Prophylactic and Therapeutic Treatment of Decompression Sickness by Heparin and Aspirin [MS thesis]. College Station, TX: Texas A&M University; 1974. 14. Wilson JR, Blessed WB, Blackburn PJ. Hyperbaric exposure during pregnancy in sheep: staged and rapid decompression. Undersea Biomed Res. 1983;10:11–15. 15. Powell MR, Smith MT. Fetal and maternal bubbles detected noninvasively in sheep and goats following hyperbaric decompression. Undersea Biomed Res. 1985;12:59–67. 16. Stock MK, Lanphier EH, Anderson DF, et al. Responses of fetal sheep to simulated no-decompression dives. J Appl Physiol Respir Environ Exerc Physiol. 1980;48:776–780. 17. Harvey EN. Bubble formation in liquids. In: Glasser O, ed. Medical Physics. Volume II. Chicago, IL: Year Book Publishers Inc; 1950:137–150. 18. Miller DL, Nyborg WL, Whitcomb CC. Platelet aggregation induced by ultrasound under specialized condition in vitro. Science. 1979;205:505–507. 19. Nemiroff MJ, Willson JR, Kirshbaum TH. Multiple hyperbaric exposures during pregnancy in sheep. Am J Obstet Gynecol. 1981;140:651–655. 20. Stock MK, Phernetton TM, Rankin JHG. Cardiovascular effects of induced decompression sickness in sheep fetus. Undersea Biomed Res. 1983;10:299–309. 21. Fife CE, Fife WP. Should pregnant women scuba dive? A review of the literature. J Travel Med. 1994;1:160–167. 22. Bolton ME. Scuba diving and fetal well-being; a survey of 208 women. Undersea Biomed Res. 1980;7:183–189. 23. Turner G, Unsworth I. Intrauterine Bends? Lancet. 1982;1:905. 24. St Leger-Dowse M, Gunby A, Moncad R, et al. Scuba diving and pregnancy: can we determine safe limits? J Obstet Gynaecol. 2006;26:509–513.

Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

Diving and pregnancy: what do we really know?

Exercise during pregnancy has been advocated by many professional organizations to promote fetal heath and maternal well-being. Those same professiona...
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