Breaking the rules: sex roles and genetic mating system of the pheasant coucal.

Generally in birds, the classic sex roles of male competition and female choice result in females providing most offspring care while males face uncertain parentage. In less than 5% of species, however, reversed courtship sex roles lead to predominantly male care and low extra-pair paternity. These role-reversed species usually have reversed sexual size dimorphism and polyandry, confirming that sexual selection acts most strongly on the sex with the smaller parental investment and accordingly higher potential reproductive rate. We used parentage analyses and observations from three field seasons to establish the social and genetic mating system of pheasant coucals, Centropus phasianinus, a tropical nesting cuckoo, where males are much smaller than females and provide most parental care. Pheasant coucals are socially monogamous and in this study males produced about 80% of calls in the dawn chorus, implying greater male sexual competition. Despite the substantial male investments, extra-pair paternity was unusually high for a socially monogamous, duetting species. Using two or more mismatches to determine extra-pair parentage, we found that 11 of 59 young (18.6%) in 10 of 21 broods (47.6%) were not sired by their putative father. Male incubation, starting early in the laying sequence, may give the female opportunity and reason to seek these extra-pair copulations. Monogamy, rather than the polyandry and sex-role reversal typical of its congener, C. grillii, may be the result of the large territory size, which could prevent females from monopolising multiple males. The pheasant coucal's exceptional combination of classic sex-roles and male-biased care for extra-pair young is hard to reconcile with current sexual selection theory, but may represent an intermediate stage in the evolution of polyandry or an evolutionary remnant of polyandry.

Cocaine use during pregnancy and intrauterine growth retardation: new insights based on maternal hair tests.

Prenatal cocaine use is more accurately measured by maternal hair assay than by urine toxicology screening or self-report. To investigate the consequences of improved measurement, the authors ascertained cocaine use during pregnancy by maternal hair test, urine test, and self-report in a sample of 691 patients recruited from one New York City hospital in 1990-1992. Associations with intrauterine growth retardation, head circumference, and length of gestation were investigated. A positive hair test at delivery was not more strongly associated with birth weight (-38.1 g; 95% CI: -164, 88.3) or head circumference (-1.73 mm; 95% CI: -5.91, 2.44) than a positive urine test at delivery (-182 g (95% CI: -295, -69.8) and -6.11 mm (95% CI: -9.99, -2.24), respectively). Cocaine concentration in hair (which was higher if urine tests were positive) had a dose-response relationship with birth weight: a 27-g decrease (95% CI: -51.9, -1.04) with each log-unit increase in concentration. Birth weights were similar among infants of never users and infants of users who stopped using cocaine before delivery. Heavier use of cocaine, but not lighter use, was associated with intrauterine growth retardation, and exposure in late pregnancy was necessary to the association. Although maternal hair tests were instrumental in clarifying these relations, their clinical use is probably not warranted.

Do clinical markers of barotrauma and oxygen toxicity explain interhospital variation in rates of chronic lung disease? The Neonatology Committee for the Developmental Network.

OBJECTIVE: To explore the hypothesis that variation in respiratory management among newborn intensive care units (NICUs) explains differences in chronic lung disease (CLD) rates. DESIGN: Case-cohort study. SETTING: NICUs at 1 medical center in New York (Babies' and Children's Hospital [Babies']) and 2 in Boston (Beth Israel Hospital and Brigham and Women's Hospital [Boston]). STUDY POPULATION: Four hundred fifty-two infants born at 500 to 1500 g birth weight between January 1991 and December 1993, who were enrolled in an epidemiologic study of neonatal intracranial white matter disorders. CASE DEFINITION: Supplemental oxygen required at 36 weeks' postmenstrual age. RESULTS: The prevalence rates of CLD differed substantially between the centers: 4% at Babies' and 22% at the 2 Boston hospitals, despite similar mortality rates. Initial respiratory management at Boston was more likely than at Babies' to include mechanical ventilation (75% vs 29%) and surfactant treatment (45% vs 10%). Case and control infants at Babies' were more likely than were those at Boston to have higher partial pressure of carbon dioxide and lower pH values on arterial blood gases. However, measures of oxygenation and ventilator settings among case and control infants were similar at the 2 medical centers in time-oriented logistic regression analyses. In multivariate logistic regression analyses, the initiation of mechanical ventilation was associated with increased risk of CLD: after adjusting for other potential confounding factors, the odds ratios for mechanical ventilation were 13.4 on day of birth, 9.6 on days 1 to 3, and 6.3 on days 4 to 7. Among ventilated infants, CLD risk was elevated for maximum peak inspiratory pressure >25 and maximum fraction of inspired oxygen = 1.0 on the day of birth, lowest peak inspiratory pressure >20 and maximum partial pressure of carbon dioxide >50 on days 1 to 3, and lowest white blood count <8 K on days 4 to 7. Even after adjusting for white blood count <8 K and the 4 respiratory care variables, infants in Boston continued to be at increased risk of CLD, compared with premature infants at Babies' Hospital. CONCLUSION: In multivariate analyses, a number of specific measures of respiratory care practice during the first postnatal week were associated with the risk of a very low birth weight infant developing CLD. However, after adjusting for baseline risk, most of the increased risk of CLD among very low birth weight infants hospitalized at 2 Boston NICUs, compared with those at Babies' Hospital, was explained simply by the initiation of mechanical ventilation.

Maternal infection, fetal inflammatory response, and brain damage in very low birth weight infants. Developmental Epidemiology Network Investigators.

Echolucent images (EL) of cerebral white matter, seen on cranial ultrasonographic scans of very low birth weight newborns, predict motor and cognitive limitations. We tested the hypothesis that markers of maternal and feto-placental infection were associated with risks of both early (diagnosed at a median age of 7 d) and late (median age = 21 d) EL in a multi-center cohort of 1078 infants <1500 x g. Maternal infection was indicated by fever, leukocytosis, and receipt of antibiotic; fetoplacental inflammation was indicated by the presence of fetal vasculitis (i.e. of the placental chorionic plate or the umbilical cord). The effect of membrane inflammation was also assessed. All analyses were performed separately in infants born within 1 h of membrane rupture (n = 537), or after a longer interval (n = 541), to determine whether infection markers have different effects in infants who are unlikely to have experienced ascending amniotic sac infection as a consequence of membrane rupture. Placental membrane inflammation by itself was not associated with risk of EL at any time. The risks of both early and late EL were substantially increased in infants with fetal vasculitis, but the association with early EL was found only in infants born > or =1 after membrane rupture and who had membrane inflammation (adjusted OR not calculable), whereas the association of fetal vasculitis with late EL was seen only in infants born <1 h after membrane rupture (OR = 10.8; p = 0.05). Maternal receipt of antibiotic in the 24 h just before delivery was associated with late EL only if delivery occurred <1 h after membrane rupture (OR = 6.9; p = 0.01). Indicators of maternal infection and of a fetal inflammatory response are strongly and independently associated with EL, particularly late EL.

Antenatal corticosteroids and cranial ultrasonographic abnormalities.

OBJECTIVE: This study was undertaken to determine whether very-low-birth-weight infants whose mothers received a course of antenatal corticosteroids were at decreased risk for 3 cranial ultrasonographic entities that predict neurodevelopmental dysfunction. STUDY DESIGN: This retrospective cohort study evaluated 1604 infants weighing 500 to 1500 g who underwent >/=1 of 3 cranial ultrasonographic scans required by design at specified postnatal intervals and whose own and mother's hospital charts were reviewed. Infants were classified according to mother's course of antenatal corticosteroids (none, partial, or complete). RESULTS: In the total sample the risks of intraventricular hemorrhage and of an echolucent image in the cerebral white matter were only modestly (and not statistically significantly) reduced after a full course of antenatal corticosteroids, whereas antenatal corticosteroids appeared to significantly reduce the risk of ventriculomegaly after even a partial course. Antenatal corticosteroids appeared to halve the risk of ventriculomegaly and echolucent image among the gestationally youngest infants and those with intraventricular hemorrhage, hypothyroxinemia, or vasculitis of the umbilical cord or chorionic plate of the placenta. CONCLUSION: These observations are consistent with the hypothesis that antenatal corticosteroids protect very-low-birth-weight infants, especially those who are most vulnerable, against the risk of cranial ultrasonographic abnormalities.

A future for epidemiology?

This paper considers ways of thinking about causes and prevention that could guide epidemiology beyond the present era. Discontent with modern epidemiology, in the face of its substantial achievements, is taken as a sign that the guiding principles of the discipline warrant reconsideration. To begin this task, current practices are placed within an historical perspective, in a review of the dominant ideas of successive eras in epidemiology. Then the premises and constraints of the present era of chronic disease epidemiology, with its risk factor paradigm, are specified. Finally, elements of a causal paradigm for an emerging era are proposed. This paradigm encourages thinking about causes at multiple levels of organization and within the historical context of both societies and individuals. The proposed approach aims to preserve and build on the contributions of past eras, as well as the present one.

Hypothyroxinemia of prematurity and the risk of cerebral white matter damage.

OBJECTIVE: Infants with hypothyroxinemia of prematurity (HOP) are at increased risk for neurodevelopmental dysfunction. Infants born near the end of the middle trimester are also at increased risk for an echolucency (EL) in the cerebral white matter, which reflects white matter damage and is the cranial ultrasound abnormality that best predicts neurodevelopmental dysfunction. We postulated that some of the increased risk of neurodevelopmental problems associated with HOP reflects an increased risk of EL. STUDY DESIGN: We studied 1414 infants weighing 500 to 1500 g who were born at 4 medical centers between 1991 and 1993. The infants had thyroxine blood levels measured during the first weeks of life, at least 1 of 3 cranial ultrasound scans performed at specified postnatal intervals, and their own and their mother's hospital charts reviewed. Infants were classified by whether or not their first thyroxine level placed them in the lowest quartile among all infants in this sample (ie, <67.8 nmol/L, our definition of HOP, equivalent to <5.3 micrograms/dL). RESULTS: After adjusting for such potential confounders as low gestational age and measures of illness severity, infants with HOP had twice the risk of EL as their peers with higher thyroxine levels. CONCLUSION: Our findings are consistent with the hypothesis that a "normal" blood thyroxine level protects infants born near the end of the middle trimester against the risk of cerebral white matter damage.

Pioneering community-oriented primary care.

PIP: This is a retrospective report on the importance of Kark and Cassel's 1952 paper on community-oriented primary care (COPC). In 1978, WHO and UNICEF endorsed COPC. However, the ideas girding and framing this approach had first been given full expression in practice some four decades earlier. In Depression-Era South Africa, Sidney Kark, a leader of the National Department of Health, converted the emergent discipline of social medicine into a unique form of comprehensive practice and established the Pholela Health Center, which was the explicit model for COPC. COPC as founded and practiced by Kark was a community, family and personal practice; it also was a multidisciplinary and team practice. Furthermore, the innovations of COPC entailed monitoring, evaluation, and research. Evaluation is the essence of Kark and Kassel's paper, which offers a convincing demonstration of the effects of COPC. Its key findings include the following: 1) that there was a decline in the incidence of syphilis in the area served by the health center; 2) that diet and nutrition improved; and 3) that the crude mortality rate as well as the infant mortality rate--the standard marker--declined in Pholela. In the succeeding decades, OPC had an international legacy (through WHO and H. Jack Geiger's influence in the US Office of Economic Opportunity), which came full circle in the 1980s, when a young generation of South Africans began to search their history for models for their health care programs at the dawn of the post-Apartheid Era.^ieng

Maternal leisure-time exercise and timely delivery.

OBJECTIVES: This study investigated whether, in a general obstetric population, exercise in pregnancy affects the timeliness of delivery. The hypothesis was that maternal exercise would not raise the risk of preterm birth. METHODS: A community cohort of 557 prenatal patients was followed up until the time of delivery. Data were collected on exercise in each trimester: none, low-moderate (< 1000 kcal [4184 kJ]/wk in energy expenditure), or heavy (> or = 1000 kcal/wk). Timely delivery was adopted as an outcome criterion. Thus, in the analysis, a term birth was treated as optimal and survival techniques were used to estimate risks for both preterm and postdates delivery. RESULTS: No association was found between low-moderate exercise and gestational length. Heavier exercise appeared to reduce, rather than raise, the risk of preterm birth. The adjusted relative risk among conditioned heavy exercisers was 0.11 (95% confidence interval = 0.02, 0.81). After term, conditioned heavy exercisers delivered faster than nonexercisers. CONCLUSIONS: The most important finding was the lack of evidence that vigorous maternal exercise is a risk factor for preterm delivery. A promising finding was that conditioned heavy exercisers have timely deliveries.

Variation in use of corticosteroids among infants < or = 1,500 grams across hospitals in three states.

We identified factors associated with no antenatal corticosteroid treatment among 1,369 women who delivered infants < or = 1,500 g and < 34 weeks gestation, 1991-1993. At four hospitals, infants weighing 500-1,500 g were enrolled. Information regarding corticosteroid use, maternal characteristics, and perinatal events were obtained. Factors associated with no corticosteroid treatment were examined in unadjusted and adjusted logistic regression models. Overall, 693 (50.6%) women did not receive corticosteroids. Two hospitals had higher rates of no corticosteroid usage (89% and 75%) as compared with the other two (32% and 50%). Black, Hispanic, and poor women were more likely to receive care at the hospitals where the rates of corticosteroid utilization were lower. Factors in the multivariate model included: < 1 or 1 day of hospitalization, vs. delivery on > or = 2 days of hospitalization (21.4: 14.5, 97.2; 4.7: 3.2, 6.9); gestational age < 26 weeks (2.7: 1.8, 4.1) or > 28 weeks (1.8: 1.3, 2.6) vs. 26-28 weeks; < 12 hours of labor vs. > 12 hours (1.7: 1.2, 2.4); delivering at hospital 2, 3, 4 vs. hospital 1 (1.6: 1.1, 2.5; 24.3: 13.6, 43.4; 10.2: 6.8, 15.3). We conclude that variations in hospital practice limit widespread use of this important antenatal treatment.