Bennu's near-Earth lifetime of 1.75 million years inferred from craters on its boulders.

An asteroid's history is determined in large part by its strength against collisions with other objects1,2 (impact strength). Laboratory experiments on centimetre-scale meteorites3 have been extrapolated and buttressed with numerical simulations to derive the impact strength at the asteroid scale4,5. In situ evidence of impacts on boulders on airless planetary bodies has come from Apollo lunar samples6 and images of the asteroid (25143) Itokawa7. It has not yet been possible, however, to assess directly the impact strength, and thus the absolute surface age, of the boulders that constitute the building blocks of a rubble-pile asteroid. Here we report an analysis of the size and depth of craters observed on boulders on the asteroid (101955) Bennu. We show that the impact strength of metre-sized boulders is 0.44 to 1.7 megapascals, which is low compared to that of solid terrestrial materials. We infer that Bennu's metre-sized boulders record its history of impact by millimetre- to centimetre-scale objects in near-Earth space. We conclude that this population of near-Earth impactors has a size frequency distribution similar to that of metre-scale bolides and originates from the asteroidal population. Our results indicate that Bennu has been dynamically decoupled from the main asteroid belt for 1.75 ± 0.75 million years.

The unexpected surface of asteroid (101955) Bennu.

NASA'S Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) spacecraft recently arrived at the near-Earth asteroid (101955) Bennu, a primitive body that represents the objects that may have brought prebiotic molecules and volatiles such as water to Earth1. Bennu is a low-albedo B-type asteroid2 that has been linked to organic-rich hydrated carbonaceous chondrites3. Such meteorites are altered by ejection from their parent body and contaminated by atmospheric entry and terrestrial microbes. Therefore, the primary mission objective is to return a sample of Bennu to Earth that is pristine-that is, not affected by these processes4. The OSIRIS-REx spacecraft carries a sophisticated suite of instruments to characterize Bennu's global properties, support the selection of a sampling site and document that site at a sub-centimetre scale5-11. Here we consider early OSIRIS-REx observations of Bennu to understand how the asteroid's properties compare to pre-encounter expectations and to assess the prospects for sample return. The bulk composition of Bennu appears to be hydrated and volatile-rich, as expected. However, in contrast to pre-encounter modelling of Bennu's thermal inertia12 and radar polarization ratios13-which indicated a generally smooth surface covered by centimetre-scale particles-resolved imaging reveals an unexpected surficial diversity. The albedo, texture, particle size and roughness are beyond the spacecraft design specifications. On the basis of our pre-encounter knowledge, we developed a sampling strategy to target 50-metre-diameter patches of loose regolith with grain sizes smaller than two centimetres4. We observe only a small number of apparently hazard-free regions, of the order of 5 to 20 metres in extent, the sampling of which poses a substantial challenge to mission success.

Probiotic use in pediatric kidney transplant recipients: What are current practices, and are they evidence-based? A pediatric nephrology research consortium study.

BACKGROUND: Probiotics are living microorganisms that may confer health benefits to their host if administered in sufficient quantities. However, data on the use of probiotics in transplant recipients are scarce. METHOD: This multi-center survey of pediatric nephrologists aimed to examine variations in practice regarding the use of probiotics in pediatric kidney transplant recipients. The survey was conducted via a 10-item questionnaire (developed in Survey Monkey) administered to pediatric nephrologists participating in the Pediatric Nephrology Research Consortium meeting in April 2023. RESULTS: Sixty-four pediatric nephrologists completed the survey. Twenty-seven (42.2%) respondents reported having prescribed probiotics to pediatric kidney transplant recipients. The primary reason for probiotic use was the treatment of antibiotic-associated diarrhea (n = 20), with other reasons including recurrent Clostridium difficile infection (n = 15), general gut health promotion (n = 12), recurrent urinary tract infections (n = 8), and parental request (n = 1). Of those who prescribed probiotics, 48.1% held them during periods of neutropenia and 14.8% during central venous line use. Of the 64 respondents, 20 reported the lack of safety data as a concern for using probiotics in kidney transplant recipients. CONCLUSION: Pediatric nephrologists are increasingly prescribing probiotics to pediatric kidney transplant recipients; nevertheless, substantial practice variations exist. The paucity of safety data is a significant deterrent to probiotic use in this population.

Numerical simulations suggest asteroids (101955) Bennu and (162173) Ryugu are likely second or later generation rubble piles.

Rubble pile asteroids are widely understood to be composed of reaccumulated debris following a catastrophic collision between asteroids in the main asteroid belt, where each disruption can make a family of new asteroids. Near-Earth asteroids Ryugu and Bennu have been linked to collisional families in the main asteroid belt, but surface age analyses of each asteroid suggest these bodies are substantially younger than their putative families. Here we show, through a coupled collisional and dynamical evolution of members of these families, that neither asteroid was likely to have been created at the same time as the original family breakups, but rather are likely remnants of later disruptions of original family members, making them second, or later, generation remnants. Our model finds about 80% and 60% of asteroids currently being delivered to near-Earth orbits from the respective families of New Polana and Eulalia are second or later generation. These asteroids delivered today in the 0.5-1 km size range have median ages since their last disruption that are substantially younger than the family age, reconciling their measured crater retention ages with membership in these families.

Spacecraft sample collection and subsurface excavation of asteroid (101955) Bennu.

Carbonaceous asteroids, such as (101955) Bennu, preserve material from the early Solar System, including volatile compounds and organic molecules. We report spacecraft imaging and spectral data collected during and after retrieval of a sample from Bennu's surface. The sampling event mobilized rocks and dust into a debris plume, excavating a 9-meter-long elliptical crater. This exposed material is darker, spectrally redder, and more abundant in fine particulates than the original surface. The bulk density of the displaced subsurface material was 500 to 700 kilograms per cubic meter, which is about half that of the whole asteroid. Particulates that landed on instrument optics spectrally resemble aqueously altered carbonaceous meteorites. The spacecraft stored 250 ± 101 grams of material, which will be delivered to Earth in 2023.

Meteoritic Evidence for a Ceres-sized Water-rich Carbonaceous Chondrite Parent Asteroid.

Carbonaceous chondrite meteorites record the earliest stages of Solar System geo-logical activities and provide insight into their parent bodies' histories. Some carbonaceous chondrites are volumetrically dominated by hydrated minerals, providing evidence for low temperature and pressure aqueous alteration1. Others are dominated by anhydrous minerals and textures that indicate high temperature metamorphism in the absence of aqueous fluids1. Evidence of hydrous metamorphism at intermediate pressures and temperatures in carbonaceous chondrite parent bodies has been virtually absent. Here we show that an ungrouped, aqueously altered carbonaceous chondrite fragment (numbered 202) from the Almahata Sitta (AhS) meteorite contains an assemblage of minerals, including amphibole, that reflect fluid-assisted metamorphism at intermediate temperatures and pressures on the parent asteroid. Amphiboles are rare in carbonaceous chondrites, having only been identified previously as a trace component in Allende (CV3oxA) chondrules2. Formation of these minerals requires prolonged metamorphism in a large (~640-1800 km diameter), unknown asteroid. Because Allende and AhS 202 represent different asteroidal parent bodies, intermediate conditions may have been more widespread in the early Solar System than recognized from known carbonaceous chondrite meteorites, which are likely a biased sampling.

Meteoroid Impacts as a Source of Bennu's Particle Ejection Events.

Asteroid (101955) Bennu, a near-Earth object with a primitive carbonaceous chondrite-like composition, was observed by the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft to undergo multiple particle ejection events near perihelion between December 2018 and February 2019. The three largest events observed during this period, which all occurred 3.5 to 6 hr after local noon, placed numerous particles <10 cm on temporary orbits around Bennu. Here we examine whether these events could have been produced by sporadic meteoroid impacts using the National Aeronautics and Space Administration's (NASA) Meteoroid Engineering Model 3.0. Most projectiles that impact Bennu come from nearly isotropic or Jupiter-family comets and have evolved toward the Sun by Poynting-Robertson drag. We find that 7,000-J impacts on Bennu occur with a biweekly cadence near perihelion, with a preference to strike in the late afternoon (~6 pm local time). This timing matches observations. Crater scaling laws also indicate that these impact energies can reproduce the sizes and masses of the largest observed particles, provided the surface has the cohesive properties of weak, porous materials. Bennu's ejection events could be caused by the same kinds of meteoroid impacts that created the Moon's asymmetric debris cloud observed by the Lunar Atmosphere and Dust Environment Explorer (LADEE). Our findings also suggest that fewer ejection events should take place as Bennu moves further away from the Sun, a result that can be tested with future observations.

Collisional formation of top-shaped asteroids and implications for the origins of Ryugu and Bennu.

Asteroid shapes and hydration levels can serve as tracers of their history and origin. For instance, the asteroids (162173) Ryugu and (101955) Bennu have an oblate spheroidal shape with a pronounced equator, but contain different surface hydration levels. Here we show, through numerical simulations of large asteroid disruptions, that oblate spheroids, some of which have a pronounced equator defining a spinning top shape, can form directly through gravitational reaccumulation. We further show that rubble piles formed in a single disruption can have similar porosities but variable degrees of hydration. The direct formation of top shapes from single disruption alone can explain the relatively old crater-retention ages of the equatorial features of Ryugu and Bennu. Two separate parent-body disruptions are not necessarily required to explain their different hydration levels.

Bright carbonate veins on asteroid (101955) Bennu: Implications for aqueous alteration history.

The composition of asteroids and their connection to meteorites provide insight into geologic processes that occurred in the early Solar System. We present spectra of the Nightingale crater region on near-Earth asteroid Bennu with a distinct infrared absorption around 3.4 micrometers. Corresponding images of boulders show centimeters-thick, roughly meter-long bright veins. We interpret the veins as being composed of carbonates, similar to those found in aqueously altered carbonaceous chondrite meteorites. If the veins on Bennu are carbonates, fluid flow and hydrothermal deposition on Bennu's parent body would have occurred on kilometer scales for thousands to millions of years. This suggests large-scale, open-system hydrothermal alteration of carbonaceous asteroids in the early Solar System.

Variations in color and reflectance on the surface of asteroid (101955) Bennu.

Visible-wavelength color and reflectance provide information about the geologic history of planetary surfaces. Here we present multispectral images (0.44 to 0.89 micrometers) of near-Earth asteroid (101955) Bennu. The surface has variable colors overlain on a moderately blue global terrain. Two primary boulder types are distinguishable by their reflectance and texture. Space weathering of Bennu surface materials does not simply progress from red to blue (or vice versa). Instead, freshly exposed, redder surfaces initially brighten in the near-ultraviolet region (i.e., become bluer at shorter wavelengths), then brighten in the visible to near-infrared region, leading to Bennu's moderately blue average color. Craters indicate that the time scale of these color changes is ~105 years. We attribute the reflectance and color variation to a combination of primordial heterogeneity and varying exposure ages.

Evidence for widespread hydrated minerals on asteroid (101955) Bennu.

Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission reveal evidence for abundant hydrated minerals on the surface of near-Earth asteroid (101955) Bennu in the form of a near-infrared absorption near 2.7 µm and thermal infrared spectral features that are most similar to those of aqueously altered CM carbonaceous chondrites. We observe these spectral features across the surface of Bennu, and there is no evidence of substantial rotational variability at the spatial scales of tens to hundreds of meters observed to date. In the visible and near-infrared (0.4 to 2.4 µm) Bennu's spectrum appears featureless and with a blue (negative) slope, confirming previous ground-based observations. Bennu may represent a class of objects that could have brought volatiles and organic chemistry to Earth.

The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements.

The top-shape morphology of asteroid (101955) Bennu is commonly found among fast-spinning asteroids and binary asteroid primaries, and might have contributed significantly to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of OSIRIS-REx, we find a significant transition in Bennu's surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennu's surface has been most recently migrating towards its equator (given Bennu's increasing spin rate), we infer that Bennu's surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior has a distribution of voids and boulders. The presence of such heterogeneity and Bennu's top-shape is consistent with spin-induced failure at some point in its past, although the manner of its failure cannot be determined yet. Future measurements by the OSIRIS-REx spacecraft will give additional insights and may resolve questions regarding the formation and evolution of Bennu's top-shape morphology and its link to the formation of binary asteroids.

Episodes of particle ejection from the surface of the active asteroid (101955) Bennu.

Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.

OSIRIS-REx Contamination Control Strategy and Implementation.

OSIRIS-REx will return pristine samples of carbonaceous asteroid Bennu. This article describes how pristine was defined based on expectations of Bennu and on a realistic understanding of what is achievable with a constrained schedule and budget, and how that definition flowed to requirements and implementation. To return a pristine sample, the OSIRIS-REx spacecraft sampling hardware was maintained at level 100 A/2 and <180 ng/cm2 of amino acids and hydrazine on the sampler head through precision cleaning, control of materials, and vigilance. Contamination is further characterized via witness material exposed to the spacecraft assembly and testing environment as well as in space. This characterization provided knowledge of the expected background and will be used in conjunction with archived spacecraft components for comparison with the samples when they are delivered to Earth for analysis. Most of all, the cleanliness of the OSIRIS-REx spacecraft was achieved through communication among scientists, engineers, managers, and technicians.

Transit time heterogeneity in canine small intestine: significance for oxygen transport.

We previously found that local O2 extraction efficacy in isolated pump-perfused intestine was enhanced when systemic reflex vasoconstriction was stimulated by hypovolemia (Samsel, R.W., and P.T. Schumacker. 1994. J. Appl. Physiol. 77: 2291-2298). The microvascular mechanism underlying this beneficial effect could involve a redistribution of flow between mucosa and serosa, or an adjustment in the heterogeneity of perfusion within those regions. We measured regional blood flows and distributions of flow and capillary erythrocyte transit times in two segments of small intestine in anesthetized dogs (n = 10). Each vascularly isolated segment of intestine was pump-perfused under high flow (O2 supply-independent VO2) and low flow (O2 supply-dependent) conditions. During the first gut segment, the animal was kept normovolemic using i.v. fluids to minimize reflex vasoconstriction. During the second, the animal was hemorrhaged to augment vasoconstriction (n = 7), or kept normovolemic to control for the effects of time (n = 3). Blood flow distributions were measured using 15 microm radiolabeled microspheres. Tissue blood volume was measured using 99mTc-labeled red blood cells. Capillary volume was determined as the product of tissue blood volume and the histologically derived fraction of vascular volume in the capillaries. Transit times were calculated as the ratio of capillary volume to flow. Each gut segment was fixed and sectioned into 350 approximately 100 mg tissue pieces for analysis. Data revealed significant spatial heterogeneity of blood flow and capillary transit times in both mucosa and muscularis, with relative dispersions (SD/Mean) ranging from 23 to 97%. Hypovolemia caused an increase in flow heterogeneity in muscularis at both high and low flow states, and in mucosa under high flow conditions. However, hypovolemia also elicited changes in capillary volume, such that transit time heterogeneity remained unchanged. Augmentation of vasoconstrictor tone caused a redistribution of flow toward mucosa (P < 0.003) under high and low flow conditions. This redistribution correlated with the improvements in O2 extraction ratio (P = 0.022). Thus, the improvement in gut O2 extraction efficacy seen with increased vasoconstriction may be explained mostly by an intramural redistribution of flow between mucosa and muscularis. Capillary transit time heterogeneity remained unchanged, suggesting that this variable is tightly regulated.

Surgical management of left-sided carcinoid heart disease.

BACKGROUND: Carcinoid involvement of left-sided heart valves has been reported in patients with a patent foramen ovale, carcinoid tumor of the lung, and active carcinoid syndrome with high levels of serotonin. The present study details the clinical features and surgical management of patients with carcinoid heart disease affecting both left- and right-sided valves. METHODS AND RESULTS: Eleven patients (7 men, 4 women) with symptomatic carcinoid heart disease underwent surgery for left- and right-sided valve disease between 1989 and 1999. Mean age was 57+/-9 years, and median preoperative NYHA class was 3. All patients had metastatic carcinoid tumors and were on somatostatin analog. Of 11 patients, 5 (45%) had a patent foramen ovale; 1 of these also had a primary lung carcinoid tumor. Surgery included tricuspid valve replacement in all patients, pulmonary valve replacement in 3 and valvectomy in 7, mitral valve replacement in 6 and repair in 1, aortic valve replacement in 4 and repair in 2, CABG in 2, and patent foramen ovale closure in 5. One myocardial metastatic carcinoid tumor was removed. There were 2 perioperative deaths. At a mean follow-up of 41 months, 4 additional patients were dead. All but 1 surgical survivor initially improved >/=1 functional class. No patient required reoperation. CONCLUSIONS: Carcinoid heart disease may affect left- and right-sided valves and occurred without intracardiac shunting in 55% of this surgical series. Despite metastatic disease that limits longevity, operative survivors had improvement in functional capacity. Cardiac surgery should be considered for select patients with carcinoid heart disease affecting left- and right-sided valves.

Posterior pericardial ascending-to-descending aortic bypass: an alternative surgical approach for complex coarctation of the aorta.

BACKGROUND: Coarctation of the aorta is commonly associated with recoarctation or additional cardiovascular disorders that require intervention. The best surgical approach in such patients is uncertain. Ascending-to-descending aortic bypass graft via the posterior pericardium (CoA bypass) allows simultaneous intracardiac repair or an alternative approach for the patient with complex coarctation. METHODS AND RESULTS: Between 1985 and 2000, 18 patients (13 males and 5 females, mean age 43+/-13 years) with coarctation of the aorta underwent CoA bypass through median sternotomy. Before operation, average New York Heart Association class was II (range I to IV), and 15 patients (83%) had systemic hypertension. One or more previous cardiovascular operations had been performed in 12 patients (67%); 10 patients had >/=1 prior coarctation repair. Two patients had prior noncoarctation cardiovascular surgery. Concomitant procedures performed in 14 patients (78%) included the following: aortic valve replacement in 9; coronary artery bypass surgery in 3; mitral valve repair in 2; and septal myectomy, mitral valve replacement, aortoplasty, subaortic stenosis resection, ventricular septal defect closure, and ascending aorta replacement in 1 patient each. All patients survived the operation and were alive with patent CoA bypass at a mean follow-up of 45 months. No graft-related complications occurred, and there were no instances of stroke or paraplegia. Systolic blood pressure fell from 159 mm Hg before surgery to 125 mm Hg after surgery. CONCLUSIONS: CoA bypass via median sternotomy can be performed with low morbidity and mortality. Although management must be individualized, extra-anatomic CoA bypass via the posterior pericardium is an excellent single-stage approach for patients with complex coarctation or recoarctation and concomitant cardiovascular disorders.

Severe aortic stenosis with low transvalvular gradient and severe left ventricular dysfunction:result of aortic valve replacement in 52 patients.

BACKGROUND: The outcome of aortic valve replacement in patients with severe aortic stenosis, low transvalvular gradient, and severe left ventricular dysfunction is not well known. METHODS AND RESULTS: Between 1985 and 1995, 52 patients with left ventricular ejection fraction (EF) < or =35% and aortic stenosis with transvalvular mean gradient <30 mm Hg underwent aortic valve replacement. The mean (+/-SD) preoperative characteristics included EF, 26+/-8%; aortic valve mean gradient, 23+/-4 mm Hg; aortic valve area, 0.7+/-0.2 cm(2); and cardiac output, 3.7+/-1.2 L/min. Simultaneous coronary artery bypass graft surgery was performed in 32 patients (62%). Perioperative (30-day) mortality was 21% (11 of 52 patients). Ten additional patients died during follow-up. Advanced age (P=0.048) and small aortic prosthesis size (P=0.03) were significant predictors of hospital mortality by univariate analysis. By multivariate analysis, the only predictor of surgical mortality was smaller prosthesis size. The only predictor of postoperative survival was improvement in postoperative functional class (P=0.04). Postoperative functional improvement occurred in most patients. Postoperative EF was assessed in 93% of survivors; 74% demonstrated improvement. Positive change in EF was related to smaller preoperative aortic valve area and female sex. CONCLUSIONS: Despite severe left ventricular dysfunction, low transvalvular mean gradient, and increased operative mortality, aortic valve replacement was associated with improved functional status. Postoperative survival was related to younger patient age and larger aortic prosthesis size, and medium-term survival was related to improved postoperative functional class.

Ebstein's anomaly: outcome of pregnancy.

OBJECTIVES: The outcome of pregnancy in Ebstein's anomaly was studied in 72 such patients (44 women, 28 men) who had had pregnancies or fathered children. BACKGROUND: Patients with Ebstein's anomaly often reach childbearing age. Reports of the outcome of pregnancy in Ebstein's anomaly are available; however, the number of patients is small. METHODS: The medical and surgical data bases at the Mayo Clinic were reviewed, and 145 patients (62 men, 83 women) of childbearing age with Ebstein's anomaly were located. All patients were contacted, and 72 patients (44 women, 28 men) with offspring were identified and reviewed in detail to assess the outcome of pregnancy. RESULTS: Forty-four women had 111 pregnancies resulting in 85 live births (76%). Seventy-six deliveries (89%) were vaginal, and nine (11%) were by cesarean section. Twenty-three deliveries were premature. There were 19 spontaneously unsuccessful pregnancies, 7 therapeutic abortions and 2 early neonatal deaths. The mean birth weight of the infants born to cyanotic women was 2.53 kg, which was significantly lower than the mean birth weight of infants born to acyanotic women (3.14 kg [p < 0.001]). The overall incidence of congenital heart disease in the 158 offspring of parents with Ebstein's anomaly was 4% (6 of 158). The incidence of congenital heart disease was 6% (5 of 83) in the offspring of women with Ebstein's anomaly and 1% (1 of 75) in that of men. There was a 0.6% (1 of 158) incidence of familial Ebstein's anomaly. There were no serious pregnancy-related maternal complications, which included maternal death, stroke, congestive heart failure, arrhythmias or endocarditis. CONCLUSIONS: Pregnancy in women with Ebstein's anomaly is well tolerated. It is associated with an increased risk of prematurity, fetal loss and congenital heart disease in the offspring. In addition, a significantly lower birth weight is found in the offspring of cyanotic versus acyanotic women with Ebstein's anomaly. Paternal Ebstein's anomaly also seems to result in an increased risk of congenital heart disease in the offspring compared with the incidence in the general population.

Pregnancy among women with congenitally corrected transposition of great arteries.

OBJECTIVES: The outcome of pregnancy in congenitally corrected transposition of the great vessels was studied in 22 women. BACKGROUND: Women with congenitally corrected transposition of the great vessels often reach childbearing age. Although reports on the outcome of pregnancy in these women are available, the number of patients is small. METHODS: The medical and surgical databases at the Mayo Clinic were reviewed, and 36 women >16 years old with congenitally corrected transposition of the great vessels were identified. All of them were contacted, and 22 who had pregnancies were identified and the outcome of pregnancy was evaluated. RESULTS: Twenty-two women had 60 pregnancies resulting in 50 live births (83%). Forty-four deliveries (88%) were vaginal and 6 (12%) were by cesarean section. One delivery was premature at 29 weeks. There was one successful twin pregnancy. There were 11 unsuccessful pregnancies. One patient developed congestive heart failure late in pregnancy because of systemic atrioventricular valve regurgitation and required valve replacement in the early postpartum period. One patient had a total of 12 pregnancies, including 1 twin pregnancy and 2 unsuccessful pregnancies. She had multiple pregnancy-related complications, including toxemia, congestive heart failure, endocarditis and myocardial infarction (single coronary artery). No other serious pregnancy-related maternal complications and no pregnancy-related deaths occurred. The mean birth weight of the infants (n = 32) was 3.2 +/- 0.4 kg. None of the 50 live offspring have been diagnosed with congenital heart disease. CONCLUSIONS: Successful pregnancy can be achieved in most women with congenitally corrected transposition of the great arteries. The rate of fetal loss and maternal cardiovascular morbidity is increased. Because of the small number of births, the risk of congenital heart disease in offspring of women with congenitally corrected transposition of the great arteries is uncertain.