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.

Cognitive development and social policy.

The city of Warsaw was razed at the end of World War II and rebuilt under a socialist government whose policy was to allocate dwellings, schools, and health facilities without regard to social class. Of the 14,238 children born in 1963 and living in Warsaw, 96 percent were given the Raven's Progressive Matrices Test and an arithmetic and a vocabulary test in March to June of 1974. Information was collected on the families of the children, and on characteristics of schools and city districts. Parental occupation and education were used to form a family factor, and the district data were collapsed into two factors, one relating to social marginality, and the other to distance from city center. Analysis showed that the initial assumption of even distribution of family, school, and district attributes was reasonable. Mental performance was unrelated either to school or district factors; it was related to parental occupation and education in a strong and regular gradient. It is concluded that an egalitarian social policy executed over a generation failed to override the association of social and family factors with cognitive development that is characteristic of more traditional industrial societies.

Maternal weight gain, infant birth weight, and diet: causal sequences.

The causal sequence maternal nutrition----maternal weight gain----infant birth weight is not sustained by available evidence except under extreme nutritional deprivation. For maternal weight change, diet effects of near starvation are unequivocal. With chronic undernutrition or social deprivation, diet effects are inapparent or modest (conditional on pregnancy stage, diet supplement, and prepregnancy weight). For birth-weight change, diet effects of near starvation are likewise unequivocal and modest with chronic undernutrition or social deprivation. The complete causal sequence has been demonstrated only below a famine threshold. Outside famine, effects are modest (conditional on baseline nutrition, timing, and content of diets, possibly also on infant sex and energy expenditure). High-protein concentrations have produced adverse effects. Micronutrients and consequent fluid retention could have favorable effects. Diet effects on birth weight apparently bypass maternal weight change. Hence, to enhance birth weight, maternal diet appears to deserve more attention than does weight gain.

Prenatal starvation and maternal blood pressure near delivery.

Maternities in cities exposed to the Dutch famine of 1944 to 1945 and in control cities were compared. Systolic blood pressure near the time of delivery was significantly reduced by exposure to famine late in the 2nd trimester and early in the 3rd trimester. Blood pressure correlated best with caloric rations in the 3rd month before delivery, and this relationship holds consistently below a ration level of 1900 cal. Above 1900 cal and up to 2200 cal (the upper limit of rations for the data analyzed) the relationship is inconsistent across cities. Edema, analyzed in one city, varied in a manner similar to blood pressure.

The effects of dietary supplementation during pregnancy on placental morphology, pathology, and histomorphometry.

We related the macroscopic and microscopic morphology and the histomorphometry of the placenta to prenatal nutritional supplementation. In the Prenatal Project, a controlled clinical trial, three dietary treatments (supplement, a high-protein beverage; complement, a balanced protein-calorie beverage, or routine vitamin and mineral tablets) were randomly allocated to poor Black pregnant women, and the outcome was assessed. Herein we report the effects on placental morphology and histomorphometry. There were significantly fewer preterm deliveries in the complement group, and this was reflected by an increase in the size of decidual cells, an index associated with placental aging. Several other characteristics of the placentas of the complement group may have been more directly associated with improved perinatal outcome: decreased intervillous fibrin, lower incidence of gross surface infarct, and smaller (and presumably less edematous) cells of the villous stroma, may have mediated increased placental perfusion. There was no evidence of any placental change associated with the increase in very preterm delivery and the highly significant depressed birth weight among preterm deliveries in the supplement group. The significantly lower incidence of meconium staining of Wharton's jelly among controls seems likely to have been a chance finding. While there were several other indices that reflected placental aging, the significantly increased chorioamnionitis, acute funisitis , and acute decidual inflammation among placentas of those who delivered prematurely [the former two associated with very early delivery (less than 35 wk gestation)] were likely to have been involved as causes of premature delivery.

Effects of prenatal nutritional supplementation on the placenta: report of a randomized controlled trial.

Protein and nucleic acid content, and RNase levels were measured in placentas collected at birth in a randomized controlled trial of prenatal nutritional supplementation in New York City. These biochemical indices were explored to understand better the effects of nutritional supplementation. (With high-protein supplements, gross measures had shown no improvement in outcome at birth and adverse effects on fetal growth, prematurity, and newborn survival; with balanced protein-calorie supplements, there was a nonsignificant rise in birth weight and longer gestation.) The biochemical indices were in general somewhat weakly related to fetal growth measures. Significant effects of nutritional treatment on the indices were minimal, and added no information that could account for gross effects observed in the fetus.

Hypertension and the risk of new-onset unprovoked seizures.

We tested the a priori hypothesis that hypertension can lead to seizures through vascular brain damage that might or might not involve manifest stroke. A case-control study with 227 patients admitted for a first unprovoked seizure and 294 acute surgical controls was carried out at Harlem Hospital Center, New York City, between 1981 and 1984. History of hypertension was significantly associated with unprovoked seizures, even after adjustment for antecedent stroke and other potential confounders (adjusted odds ratio [OR] = 1.57; 95% confidence limit [CL], 1.0 to 2.44). There was marked synergism between history of stroke and history of hypertension; subjects with a history of both had a fourfold increase in seizure risk compared with subjects with neither (adjusted OR = 4.07; 95% CL, 1.50 to 11.0). In these data, history of hypertension appears to be an independent risk factor for new-onset unprovoked seizures, especially, but not only, in conjunction with a history of stroke.

Causal thinking in practice: strengths and weaknesses of the clinical vantage point.

The place of causal inference in clinical practice is considered. One function relates to the validation of existing knowledge, as in the evaluation of the medical literature, and is exemplified by the process of editorial selection. A second function relates to the validation of potential knowledge, as in the testing of hypotheses, and is exemplified by the pursuit of a nutritional cause of retarded mental development. Features of clinical practice that contribute strengths or weaknesses to causal inference are then examined. These include the diagnostic process, the effect of cumulative clinical experience, continuity of observation and follow-up, and the focus on disease.

A randomized controlled trial of prenatal nutritional supplementation in New York City.

This randomized controlled trial of nutritional supplementation in pregnancy, in a poor black urban population in the United States, aimed to increase the birth weight and influence the postnatal development of the offspring of mothers at high risk of having low birth weight infants. The execution of the research design and adherence to the treatment regimen among the experimental population appeared adequate for a reasonable test of the treatments. At birth, the only significant favorable effect of supplementation observed was the prevention of depressed birth weight among the offspring of mothers who smoked heavily. With balanced protein-calorie supplementation, length of gestation was increased, the proportion of low-birth-weight infants reduced, and mean birth weight raised by 41 gm (not statistically significant). With high protein supplementation, there was an excess of very early premature births and associated neonatal deaths, and there was significant growth retardation up to 37 weeks of gestation. At 1 year of age, significant effects of high protein supplement were found on three psychological measures: visual habituation, visual dishabituation, and mean length of free play episodes. These measures were unrelated to measures of growth at birth and at 1 year of age. There were no detectable residual adverse effects of high protein supplementation at 1 year of age.

Age at death used to assess the effect of interhospital transfer of newborns.

In New York City, newborn units classified as level 1 (no intensive care) frequently transfer low-birth-weight infants to units classified as level 3 (complete intensive care), but level 2 units (those with intermediate levels of care) transfer rarely. As deaths occurring in the first hours of life are unlikely to be affected by infant transport services, early (first four hours), late (four hours to 28 days), and overall neonatal death rates were separately examined at each of the three levels of care for singleton live-births weighing 501 to 2,250 g. As previously reported, overall neonatal mortality (adjusted for birth weight, gestational age, sex, and race) for births at level 1 units (163.0/1,000) and level 2 units (168.1/1,000) was similar, and rates for births at level 3 (128.0/1,000) were significantly lower. Mortality up to four hours, and from four hours to 28 days, however, differed between level 1 and level 2 units. Among early deaths, the mortality for level 1 births was 68.0/1,000, significantly higher than both the rate for level 2 births (46.0/1,000) and for level 3 births (40.6/1,000). Between four hours and 28 days, mortality relative to level 3 improved for level 1 births, but worsened for level 2 births. For infants with birth weight less than 1,251 g, for whom transport rates from level 1 units are highest, mortality in level 1 births was higher than in level 2 births only until 18 hours of life; thereafter, level 2 mortality was higher.(ABSTRACT TRUNCATED AT 250 WORDS)

Medical care and preterm infants of normal birth weight.

Preterm infants of normal birth weight (born before 37 completed weeks of gestation and weighing more than 2,250 g) experience a neonatal mortality risk almost four times higher than do term infants in the same weight range. In an analysis of the effect of hospital level of birth on neonatal mortality, such preterm normal weight infants were found to experience higher mortality if born outside of a Level 3 (tertiary care) center. For all singleton infants in this weight-gestation category born in New York City maternity services during a 3-year period (N = 23,257), the relative mortality risk for Level 1 births (compared with Level 3) was 1.72 (P less than .01) and for Level 2 births 1.47 (P less than .05). The excess mortality at Level 1 and Level 2 units was almost entirely due to a more than twofold higher death rate in black infants born in these units. Several potentially confounding socioeconomic, demographic, and biologic variables entered into a logistic regression model could not account for the higher mortality rates for black infants born in Level 1 and Level 2 units. Among black infants born at Level 1 units, deaths in preterm normal birth weight infants were less likely to occur in a receiving tertiary care center than were either deaths in low birth weight infants or deaths in term normal weight infants, suggesting that the need for special care of preterm normal birth weight infants is underestimated in some hospitals without newborn intensive care units.

Cranial ultrasound prediction of disabling and nondisabling cerebral palsy at age two in a low birth weight population.

OBJECTIVE: To employ multivariate analytic techniques to assess the association between neonatal cranial ultrasound (US) abnormalities and subsequent cerebral palsy (CP), defined as disabling CP (DCP) or nondisabling CP (NDCP) depending on the level of motor dysfunction. DESIGN: Prospective cohort study. SUBJECTS AND METHODS: The Neonatal Brain Hemorrhage Study enrolled a geographically representative sample of 1105 newborns 501 to 2000 g and obtained follow-up data on 777 (86%) of the 901 survivors at age two. One hundred thirteen children (14.6%) had motor findings severe enough to classify them as having CP. The 61 (7.9%) of these children who were disabled by their motor impairment we classified as having DCP. The remaining 52 (6.7%) who had definite neurologic findings (usually mild spastic diplegia) but without evidence of interference with daily living, we classified as having NDCP. RESULTS: In a multivariate logistic regression model of perinatal and postnatal variables, the following factors were found to be significant risk factors for DCP: parenchymal echodensities/lucencies or ventricular enlargement (PEL/VE) on cranial US (OR = 15.4; 7.6, 31.1), germinal matrix/intraventricular hemorrhage (GM/IVH) (OR = 3.5; 1.7, 6.9) and mechanical ventilation (OR = 2.9; 1.2, 7.1). Fully 93.4% of infants were correctly classified as to presence or absence of DCP on the basis of this model. Birth weight, gestational age, length of hospital stay, gender, race, plurality, presence of labor and Apgar score were not significant independent predictors of DCP. For NDCP, the only risk factor significant in the multivariate model was PEL/VE (OR = 5.3; 2.2, 12.6). CONCLUSIONS: Among perinatal and postnatal factors, cranial US abnormalities are by far the most powerful predictors of disabling CP in low birth weight infants. Although PEL/VE was the strongest predictor, GM/IVH also appeared to independently contribute to the risk of DCP. NDCP in low birth weight infants appears to have a different risk profile than DCP. In particular, it is less closely related to US evidence of perinatal brain injury.

Epidemiologic detection of low dose effects on the developing fetus.

Evaluations of the health effects of exposures in the workplace and environment have broadened to include effects on reproduction, as well as on the development of cancer. Models to assess risks associated with varying doses of exposure rest almost entirely on data about cancer. In this paper we discuss some distinctive features of reproduction which bear on the interpretation of such models, when applied to reproduction, rather than carcinogenesis. Dose-response curves describe the relationship between two exposures (smoking and alcohol drinking) and two outcomes (spontaneous abortion and birthweight) are used to illustrate some of the questions which arise in attempting to determine a "safe" level of exposure.

PIP: This paper examines the ways in which evaluation of risks of exposure to noxious substances differ in the field of reproduction from the risks of carcinogenesis, and presents models of the effects of varying doses of exposures to smoking and alcohol drinking on spontaneous abortion and birthweight. Models to assess risks associated with varying doses of exposure are almost all based on data about cancer, but the models for risk assessment in reproduction and in oncogenesis differ in at least 3 fundamental ways: 1) the range of relevant adverse reproductive outcomes is more varied and may involve different underlying mechanisms; 2) the relation of timing and duration of exposure to outcome may be different in reproductive endocrinology and in oncogenesis, with many morphological effects depending on exposure at a precise and relatively short period of development; and 3) in reproduction, the exposure can effect 2-3 individuals, although the outcome is usually described in terms of the fetus or infant only. 1 advantageous aspect of the biology of reproduction that has no parallel in carcinogenesis for the study of modest effects is that, for anomalies that are lethal in utero, the search for etiologic factors among aborted fetuses is considerably more parsimonious in terms of the numbers of pregnancies which need to be studied than a similar search among births would be. For example, the sample sizes for exposed and unexposed populations which would be needed to detect, with 80% statistical power, a doubling of the rate of trisomy 21 at conception would be 15,217 births or 1117 abortions. A study of dose-response relations of exposure to smoking and alcohol drinking on spontaneous abortion and birthweight was based on data drawn from an ongoing epidemiological study in 3 New York City hospitals which compares women admitted with spontaneous abortion to a comparison group matched for maternal age and payment status whose pregnancies continued longer than 28 weeks. The data indicate a dose-response relationship between the number of cigarettes smoked each day and both spontaneous abortion and lowered birthweight. In both instances, a logarithmic curve best described the data. A dose-response relationship was also found between alcohol drinking and spontaneous abortion; the odds of abortion increase linearly with increases in the number of days each month on which alcohol is consumed. No relation was found between smoking and alcohol drinking in their effects on spontaneous abortion. The relationship between the exposures of alcohol drinking and smoking and the outcomes of spontaneous abortion and birthweight are used to illustrate some of the problems in attempting to determine a safe level of exposure.

Data collection strategies in genetic epidemiology: The Epilepsy Family Study of Columbia University.

A large-scale study of genetic influences on seizure disorders is described here as a primer of tested methods for collection of family history data. 1957 adult probands with epilepsy were ascertained from voluntary organizations. Personal and family history data were obtained from probands in semistructured telephone interviews. To increase sensitivity, an independent family history was obtained from a second family informant in a similar interview. To increase specificity and diagnostic detail, family members reported to be affected were interviewed, and medical records of probands and affected relatives were collected. Participation rates for probands were 84-90%. Interviews were completed with second informants in 67% of families, and with 51% of eligible affected relatives. The main reasons for non-interview were lack of permission from probands and difficulties in locating relatives. Although 90% of probands gave verbal permission for medical record review, only 75% of these signed and returned consent forms for this purpose. Physicians returned 87% of the records requested. The resulting proportion of probands with medical records was 59%. These findings illustrate the complexity involved in assembling useful databases in genetic epidemiology.

Voluntary health agencies as target populations for epidemiologic research.

The ability of two voluntary health agencies to provide suitable target populations for epidemiologic research was explored in a pilot study of epilepsy. The results suggest that, properly approached, voluntary agencies offer advantage for this purpose. In the first agency (Group A), subjects were recruited by mail, producing a response rate of 15%. In the second agency (Group B), subjects were recruited by telephone, producing a response rate of 87%. A structured, precoded telephone interview about personal and family history of seizure disorders was administered to both groups of subjects. Subjects in Group A gave permission to contact a higher proportion of their eligible relatives than did those in Group B (73 vs 57%). Permission was obtained more often for relatives reported to have had seizures (Group A 86%, Group B 78%) than for other relatives. 89% of relatives contacted directly agreed to be interviewed. Consent forms for medical record review were signed and returned by 95% of Group A and 77% of Group B subjects. Diagnoses of etiology and seizure type of epilepsy based on the interview data agreed with diagnosis based on the medical records in most cases. In first-degree relatives of subjects with epilepsy, reported rates of epilepsy did not appear to be seriously biased.

Early ultrasound dating of pregnancy: selection and measurement biases.

Can using early ultrasound examinations to date pregnancy introduce information bias in perinatal research? Our purpose was to identify determinants of early ultrasound examinations and to compare early ultrasound to menstrual history dating. Between January 1987 and June 1989, 1159 white, largely middle class, prenatal patients were contacted for a prospective observational study. 876 (76%) agreed to participate. Of these 764 (87%) met the eligibility criteria for this analysis, namely singleton pregnancy, delivered after 20 weeks (spontaneous or induced, vaginal or c-section), with prenatal chart abstracted. Selection factors for early ultrasound identified in multivariate analysis were: bleeding in early pregnancy, OR = 1.9 (1.0, 3.5), attendance at health maintenance organization OR = 7.2 (3.4, 15), no insurance or Medicaid only OR = 0.3 (0.1, 0.6), and increasing time from last menstrual period to first prenatal visit in weeks OR = 0.89 (0.85, 0.93). In conformity with previous results, ultrasound dating of pregnancy led to a higher estimate of preterm delivery (10 vs 7.6%), a higher estimate of term delivery (87.2 vs 82.7%) and a lower estimate of postterm delivery (2.8 vs 9.7%) than dating by menstrual history, p < 0.001. Selection factors and measurement issues, such as those described here, could introduce bias and should be carefully considered in the design, analysis and interpretation of perinatal research.

Background gamma radiation and childhood cancers within ten miles of a US nuclear plant.

In light of some recent reports concerning childhood leukaemia near nuclear installations, we examined rates of cancer in children in relation to background gamma ray exposure. Data from a national monitoring programme around nuclear facilities were used to map the distribution of background gamma radiation for 69 small geographical subunits (average population 2300) within ten miles of one US nuclear plant. An association was found for incidence of childhood cancers as a whole (odds ratio (OR) = 2.4; 95% confidence limits (CL) 1.2, 4.6). For leukaemias specifically, the odds ratio was also elevated but confidence limits were very wide (OR = 2.4; 95% CL 0.5, 12.9). Analyses adjusting for sociodemographic characteristics of study tracts (population density and income) gave similar results; data on other risk factors were unavailable. Conventional risk models would not predict a detectable increase in childhood cancer from background gamma radiation, particularly not an increase of this magnitude. The large effect for solid tumours as well as leukaemias is also somewhat counter to expectation. Since a priori the association we observed was unlikely, it is important to know if similar trends in childhood cancer with background radiation are seen in other areas before rejecting chance or bias as an explanation for the result.

Timing in prenatal nutrition: a reprise of the Dutch Famine Study.

The array of results discussed in this paper is assembled by stage of gestation in the following table (Table 1). We must allow some uncertainty for some outcomes as to the precise stages of gestation in which they originate. For instance, with obesity, the effects of famine exposure may extend beyond the first trimester into the second. Yet, the table is perhaps sufficient in itself to support the point with which the paper opened, namely, that stage of development is crucial to the appreciation of the effects of prenatal nutrition.