Seasonal variation in conception and various pregnancy outcomes

Abstract

U.S. vital registration data on live births and data on abortions and ectopic pregnancies from a national hospital discharge survey were used to examine the seasonality of conceptions and the influence the conception pattern has on the monthly incidence of abortions and ectopic pregnancies. We found that in the United States conceptions follow a consistent seasonal pattern with the peak in November and December. However, when the pattern for conceptions is controlled, the monthly variation for abortions and ectopic pregnancies is not significant. Therefore, we find no monthly excess for any of these outcomes of pregnancy over that expected as a consequence of the seasonality of conception. We suggest the monthly variation for the number of each of these pregnancy outcomes will best be explained when the seasonal variation in conceptions is understood.     

Effects of maternal birth season on birth seasonality in the Canadian population during the seventeenth and eighteenth centuries

Birth records of the French-Canadian population for the period 1621-1765 were analyzed retrospectively to examine the effect of maternal birth season on the seasonal distribution of births. Preliminary examination indicated that there was a bimodal pattern in birth seasonality: a major peak in early spring, a trough in early summer, a minor peak in autumn, and a trough around December. Because this seasonality was strongly biased at the level of the first birth by the month of marriage, which was concentrated in November, the seasonality of nonfirst births (n = 32,926) was examined in relation to the four seasons of maternal birth. Mothers born in May-July showed a flatter monthly distribution of nonfirst births at a maternal age of 28 years or more. Analysis of marriage-first birth intervals indicated that mothers who married in August-October showed a lower percentage of immediate conception (intervals of 8-10 months), whereas those mothers born in May-July had a higher percentage of immediate conception. This difference in birth seasonality shown by mothers born in May-July is similar to results from early twentieth-century Japan. Some seasonal infertility factors could have affected the embryos at the earliest stage of pregnancy, modifying a part of the seasonal variation in birth rate.     

Population biology of the metacercariae of Centrocestus formosanus (Trematoda: Heterophyidae) on the gills of Aplocheilus panchax

The population biology of metacercariae of Centrocestus formosanus (Nishigori, 1924) on the gills of the larvivorous fish, Aplocheilus panchax (Hamilton) was investigated based on data from examination of monthly samples of fish collected from a stream at Visakhapatnam during the period December 1983 to April 1986. The seasonal dynamics, dispersion pattern and long-term changes were studied. No seasonality in prevalence and density of infection with metacercariae was observed. The recruitment of metacercariae occurred throughout the year. An increase in density of infection with increase in size of the fish was noted. Possible reasons for the observed distribution are discussed. The frequency distribution of the metacercariae followed the negative binomial at different times of the year. The data indicated an increase in degree of overdispersion with increase in size offish except for a slight drop in the largest size class. Long-term changes in the abundance of metacercariae are given and a decline in parasite population abundance is noted.     

Seasonality of births is associated with seasonality of marriages in Malta

This study was carried out to quantify secular trends in seasonal variation in births in Malta, a small Mediterranean country where the vast proportion of births occur in wedlock due to a predominantly Roman Catholic population. It also related such variations to seasonal variation in marriages. Annual seasonal peaks of marriages and births were analysed over the period 1950-1996 by X11 ARIMA. A significant peak in marriages (n = 111,932) in the third quarter of the year was found for almost the entire period under study. This was paralleled by a peak in births (n = 299,558) for the period 1970-1996, which lagged after the peak in marriages by 13-14 months. For the period 1994-1996, when monthly data for monthly pregnancies were available by pregnancy order, the peak in births was caused by first pregnancies only. Seasonal patterns in births occur almost universally due to cultural and/or biometeorological factors. The best known patterns include those of the southern United States, where births decline in April and May, and in northern Europe, where births peak in March and April. In Malta, the late summer peak in births appears to be due to a practical and planned approach by Maltese couples to contraceptive planning, probably influenced by the Roman Catholic ethos and social pressures, with unprotected intercourse occurring only after marriage. In Malta, birth control, albeit by so-called natural methods, was introduced in the 1960s. Prior to this period, births peaked towards the beginning/end of the year, and this may be the more natural seasonality of births in Malta.     

Effect of energy availability, seasonality, and geographic range on brown bear life history

Life-history theory allows predictions of how changes in environmental selection pressures along a species' geographic distribution result in discrete shifts in life-history traits. We tested for spatial patterns of 24 populations of brown bears Ursus arctos across North America that grouped according to the following environmental and population parameters: evapotranspiration as a correlate of primary productivity of vegetation, coefficient of variation of monthly evapotranspiration values as a measure of seasonality. population density, and adult female weight. Cluster analysis grouped brown bear populations into two regions: Pacific-coastal populations characterized by high population density and large females that lived in areas of high primary productivity and low seasonality. and inland and barren-ground populations characterized by relatively low density and small bears that lived in areas of low productivity and high seasonality. For each region, we tested whether life-history traits (age at maturity and interbirth interval) related to primary productivity or seasonality. High altitude (interior: > 1000 m) and high latitude (barren-ground; >65°N) populations respond to extremes in seasonality with risk-spreading adaptations. For example, age at maturity and interbirth interval increased with greater seasonality. In contrast, Pacific-coastal populations living on the western edge of brown bear geographic range respond to intraspecific competition at high densities by maximizing offspring competitive ability. For example, age at maturity increased with greater primary productivity and high population density. In each region, the female parent decided on the life-history trade-offs required to reduce the risks of offspring mortality depending on the environmental pattern.     

High risk maternal factors related to fetal wastage in rural Bangladesh

An analysis of the relationship between fetal mortality (early fetal death and stillbirth), pregnancy order, maternal age, and previous fetal deaths in a rural Bangladesh population characterized by high fertility and mortality and the virtual absence of obstetric and other medical care indicates that early fetal wastage and stillbirth are higher among pregnancy orders 1 and 6, or higher than among orders 2 and 3, with the increased risk particularly apparent among those pregnancies following 2 or more previous fetal deaths. The data consist of the 21,144 pregnancies that occurred to the women in Matlab, Bangladesh, 1966-1969. By a multiple regression technique allowing for pregnancy order and previous fetal deaths, adjustments were made for age of the mother, and after allowances were made for previous fetal deaths, adjustments were made for pregnancy order. Results show the fewest fetal deaths in 2nd and 3rd pregnancies, and most at the highest parities. 10% of all pregnancy terminations 1966-1969 were registered as fetal deaths. Women in the higher pregnancy orders who have not experienced previous fetal deaths or only 1 fetal death have only a slight increase in the risk of fetal death compared to women in pregnancy orders 2 and 3. It is concluded that the virtual absence of medical care facilities is responsible for the large numbers of fetal deaths due to complications of gestation, delivery, and environmental influences. It also results in a higher maternal mortality of women with pregnancy complications related to fetal deaths. This absence of obstetric care and the high maternal mortality in this population may allow only women without reproductive impairments to reach the higher pregnancy orders.     

Level,Trend and Correlates of Mistimed and Unwanted Pregnancies among Currently Pregnant Ever Married Women in India

Unintended pregnancy accounts for more than 40% of the total pregnancies worldwide. An Unintended pregnancy can have serious implications on women and their families. With more than one-fourth of the children in India born out of unintended pregnancies such pregnancies are considered to be one of the major public health concerns today. The present study is aimed at determining major predictors of unintended pregnancy among currently pregnant ever-married women in India. The present study has used National Family Health Survey (NFHS) data, conducted by the International Institute for Population Sciences (IIPS), Mumbai, to show the trend, pattern and determinants of mistimed and unwanted pregnancies. Bivariate and multinomial logistic regression model have been used with the help of Stata 13 software. The results show that the likelihood of a mistimed pregnancy is more prevalent among young women whereas the prevalence of unwanted pregnancy is observed more among the women aged 35 years or more. The results also show that the risk of experiencing mistimed pregnancy decreases if the woman belongs to ‘other’ castes and has higher education. The likelihood of unwanted pregnancy decreases among married women aged 18 years and above, those women having higher education, some autonomy and access to any mode of mass communication. Knowledge of these predictors of mistimed and unwanted pregnancy will be helpful in identifying the most vulnerable group and prioritize the intervention strategies of the reproductive health programmes for the population in need.     

The seasonality of births in Canada

Earlier studies on the seasonality of births indicate that a major peak occurs in August and September and a minor peak in January and February. This study uses the 1984 Canadian Fertility Survey data on reproductive history to examine birth and pregnancy seasonalities, and shows that the 'worst' months for births are January and February and the 'best' months are March, April and May. There is no systematic pattern in the seasonality of pregnancies, possibly because effective birth control allows couples to plan the timing of births.     

Utilizing Longitudinal Measures of Fetal Growth to Create a Standard Method to Assess the Impacts of Maternal Disease and Environmental Exposure

Impaired or suboptimal fetal growth is associated with an increased risk of perinatal morbidity and mortality. By utilizing readily available clinical data on the relative size of the fetus at multiple points in pregnancy, including delivery, future epidemiological research can improve our understanding of the impacts of maternal, fetal, and environmental factors on fetal growth at different windows during pregnancy. This study presents mean and standard deviation ultrasound measurements from a clinically representative US population that can be utilized for creating Z-scores to this end. Between 2006 and 2012, 18, 904 non-anomalous pregnancies that received prenatal care, first and second trimester ultrasound evaluations, and ultimately delivered singleton newborns at Brigham and Women’s hospital in Boston were used to create the standard population. To illustrate the utility of this standard, we created Z-scores for ultrasound and delivery measurements for a cohort study population and examined associations with factors known to be associated with fetal growth. In addition to cross-sectional regression models, we created linear mixed models and generalized additive mixed models to illustrate how these scores can be utilized longitudinally and for the identification of windows of susceptibility. After adjustment for a priori confounders, maternal BMI was positively associated with increased fetal size beginning in the second trimester in cross-sectional models. Female infants and maternal smoking were associated with consistently reduced fetal size in the longitudinal models. Maternal age had a non-significant association with increased size in the first trimester that was attenuated as gestation progressed. As the growth measurements examined here are widely available in contemporary obstetrical practice, these data may be abstracted from medical records by investigators and standardized with the population means presented here. This will enable easy extension of clinical data to epidemiologic studies investigating novel maternal, fetal, and environmental factors that may impact fetal growth.     

Birth seasonally among peasant cultivators: The interrelationship of workload,diet, and fertility

The monthly distribution of live births was analyzed over a 51-year period, 1926–1976, for a rural Taiwan fishing community. Unlike previous studies of birth seasonality, monthly distributions of births did not deviate from what would be expected by chance. This new case is shown to be consistent with the suggestion, developed by Pasternak during a study of birth seasonality in two Taiwan farming communities, that for peasant cultivators the annual cycle of production exerts a more decisive influence on birth seasonality than time of marriage or attributes of temperature, rainfall, or workload. An hypothesis that links the productive cycle to conceptions through the intervening variable of diet is presented and successfully tested using several sets of data on monthly births. A direct effect of nutrition on human fertility, suggested by recent studies of reproductive performance under conditions of nutritional stress, may largely explain seasonality of conceptions and births in populations that experience significant seasonal variation in diet.The Cross Harbor data presented in this paper were collected as part of an ongoing investigation of the comparative demography and social structure of fishing, farming, and market town communities located within a particular Chinese regional system. The support of the National Science Foundation during the period of fieldwork is gratefully acknowledged. I wish to thank G. William Skinner, William H. Durham, Greg Acciaioli, Steven Sangren, Chuang Miao-huei, Harumi Befu, and Philip L. Ritter for their comments on earlier drafts of the present article. I owe a special debt of gratitude to Burton Pasternak (City University of New York), who intellectually inspired and personally encouraged the writing of this paper.     

Unintended pregnancies and exposure to potential human teratogens

BACKGROUND: We aimed to investigate the risk factors associated with unintended pregnancies as well as the association between unintended pregnancies and potential teratogenic exposures. METHODS: A cross-sectional survey was performed among women attending the Maternity School of the Samsung Cheil Hospital and Women's Health Care Center in Seoul, Korea. Demographic data, obstetric history, socioeconomic status, intention to become pregnant, and exposure to potential teratogens were obtained. RESULTS: A total of 1354 women with median age of 29 years and median gestational age of 29 weeks were included. Of these, an educational level above high school was 74.2%, primigravida was 77.3% and unintended pregnancy was 48%. In the logistic regression analysis, women younger than 24 years of age had a relative risk (RR) of 2.5 (95% confidence interval [CI], 1.3-4.7) of having an unintended pregnancy and women with lower household monthly income level had a RR of 1.3 (95% CI, 1.0-1.6). Women with unintended pregnancies had an RR of 1.9 (95% CI, 1.5-2.5), 3.0 (95% CI, 2.0-4.5), 1.5 (95% CI, 1.0-2.3), 2.9 (95% CI, 1.1-7.2), and 2.0 (95% CI, 1.62.4) of being exposed to alcohol, medications, cigarette smoking, X-rays, or to any of these, respectively, during the first trimester of pregnancy. CONCLUSIONS: Unintended pregnancies are more likely to occur among young women with a lower household monthly income level. Prenatal counseling should be especially recommended for women with unintended pregnancies in order to evaluate whether they have been exposed to potential teratogenic agents.     

Influence of past reproductive performance on risk of spontaneous abortion.

OBJECTIVE--To investigate the incidence of spontaneous abortion in a population of women in order to establish their risk of spontaneous abortion and the obstetric factors predisposing to it. DESIGN--Prospective study of women recruited by radio and poster appeal and from hospital outpatient clinics. SETTING--English provincial community. PATIENTS--630 Women from the general population intending to become pregnant. INTERVENTIONS--The viability of the pregnancy was assessed by abdominal ultrasonography before completion of the eighth week, and the assessment was repeated if vaginal bleeding occurred. MAIN OUTCOME MEASURE--Spontaneous abortion or live births in women with or without a previous history of spontaneous abortion. RESULTS--The overall incidence of clinically recognisable spontaneous abortion before 20 weeks of gestation was 12% (50/407 pregnancies). The risk of spontaneous abortion in each category of patient was classified with respect to the patient''s past reproductive performance and found to be influenced greatly by her previous obstetric history. In primigravidas and women with a history of consistently successful pregnancies the incidences of abortion were low (5% (4/87) and 4% (3/73) respectively), whereas women with only unsuccessful histories had a much greater risk of aborting the study pregnancy (24% (24/98)), even when their sole pregnancy had ended in abortion (20% (12/59)). The outcome of the last pregnancy also influenced the outcome of the study pregnancy; only 5% of women (5/95) whose previous pregnancy had been successful aborted, whereas the incidence of loss of pregnancy among women whose last pregnancy had aborted was 19% (40/214). CONCLUSIONS--A knowledge of the patient''s reproductive history is essential for the clinical assessment of her risk of spontaneous abortion. As the most important predictive factor for spontaneous abortion is a previous abortion, the outcome of a woman''s first pregnancy has profound consequences for all subsequent pregnancies.     

Seasonality of a Diverse Beetle Assemblage Inhabiting Lowland Tropical Rain Forest in Australia

One of the least understood aspects of insect diversity in tropical rain forests is the temporal structuring, or seasonality, of communities. We collected 29,986 beetles of 1473 species over a 4-yr period (45 monthly samples), with the aim to document the temporal dynamics of a trophically diverse beetle assemblage from lowland tropical rain forest at Cape Tribulation, Australia. Malaise and flight interception traps were used to sample adult beetles at five locations at both ground and canopy levels. Beetles were caught throughout the year, but individual species were patchy in their temporal distribution, with the 124 more abundant species on average being present only 56 percent of the time. Climatic variables (precipitation, temperature, and solar radiation) were poorly correlated with adult beetle abundance, possibly because: (1) seasonality of total beetle abundance was slight; (2) the peak activity period (September–November) did not correspond to any climatic maxima or minima; or (3) responses were nonlinear owing to the existence of thresholds or developmental time-lags. Our results do not concur with the majority of tropical insect seasonality studies suggesting a wet season peak of insect activity, perhaps because there is no uniform pattern of insect seasonally for the humid tropics. Herbivores showed low seasonality and individual species' peaks were less temporally aggregated compared to nonherbivores. Canopy-caught and larger beetles (> 5 mm) showed greater seasonality and peaked later in the year compared to smaller or ground-caught beetles. Thus seasonality of adult beetles varied according to the traits of feeding ecology, body size, and habitat strata.     

High-risk pregnancy and hypoluteoidism in the bitch

High-risk pregnancies are those in which the prevalence of maternal, fetal and/or perinatal morbidity or mortality is likely to be higher than that of the general obstetrical population. Some maternal characteristics associated with risk to maternal, fetal and/or perinatal health are readily identifiable prior to conception, such as advanced maternal age, brachycephalic breed, or a previous history of pregnancy loss. Others, such as gestational diabetes or a singleton litter, are recognized after conception. Early recognition of the problem (i.e. the risk), anticipation of the potential sequelae, and development of an aggressive management scheme are essential for a successful outcome of a high-risk pregnancy. A previous history of pregnancy loss is a high-risk factor for recurrence during subsequent pregnancies. Infection is a common cause. In some instances, recurrent pregnancy loss is associated with low serum concentrations of progesterone. Although the mechanism(s) by which this occurs is not fully understood, the situation has been called hypoluteoidism. Whatever the cause of the risks to pregnancy, the goals of managing high-risk pregnancies are to optimize maternal, fetal and perinatal health, so as to maintain maternal health throughout pregnancy and lactation and maximize the number of healthy pups surviving to weaning age.     

Incidence of low birth weight infants born to mothers with multiple risk factors

Low birth weight (LBW) is associated with a large number and variety of risk conditions during pregnancy. The number and types of risk conditions per pregnancy were determined in 1,864 white and 872 black mothers delivered at the University of Kansas Medical Center between 1975 and 1978. The incidence of LBW infants increased steadily among white and black mothers as the number of risk factors increased from none to three or four per pregnancy. Among pregnancies without spontaneous premature rupture of membranes (PROM), 51 percent of the LBW infants were born to mothers who had multiple risk factors associated with their pregnancies, even though only 18 percent of these pregnancies were associated with multiple risk factors. Among pregnancies with PROM, 72 percent were associated with multiple risk conditions, and 31 percent resulted in LBW infants. About 90 percent of LBW infants from PROM pregnancies had mothers with multiple risk factors. For all numbers of risk conditions, black mothers had a higher incidence of LBW infants than white mothers. Among black mothers without spontaneous premature rupture of membranes (PROM), the incidence of LBW infants increased from 3.2 percent (10/308) in low (zero)-risk condition pregnancies to 33 percent (16/49) among mothers with three or four risk conditions during the pregnancy. Among white mothers without PROM, the incidence of LBW infants increased from 1.7 percent (12/708) in low (zero)-risk condition pregnancies to 30 percent (19/64) in pregnancies with three or four risk conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

High-risk pregnancy and hypoluteoidism in the bitch

High-risk pregnancies are those in which the prevalence of maternal, fetal and/or perinatal morbidity or mortality is likely to be higher than that of the general obstetrical population. Some maternal characteristics associated with risk to maternal, fetal and/or perinatal health are readily identifiable prior to conception, such as advanced maternal age, brachycephalic breed, or a previous history of pregnancy loss. Others, such as gestational diabetes or a singleton litter, are recognized after conception. Early recognition of the problem (i.e. the risk), anticipation of the potential sequelae, and development of an aggressive management scheme are essential for a successful outcome of a high-risk pregnancy. A previous history of pregnancy loss is a high-risk factor for recurrence during subsequent pregnancies. Infection is a common cause. In some instances, recurrent pregnancy loss is associated with low serum concentrations of progesterone. Although the mechanism(s) by which this occurs is not fully understood, the situation has been called hypoluteoidism. Whatever the cause of the risks to pregnancy, the goals of managing high-risk pregnancies are to optimize maternal, fetal and perinatal health, so as to maintain maternal health throughout pregnancy and lactation and maximize the number of healthy pups surviving to weaning age.     

Harnessing the Medicaid Analytic eXtract (MAX) to Evaluate Medications in Pregnancy: Design Considerations

Background

In the absence of clinical trial data, large post-marketing observational studies are essential to evaluate the safety and effectiveness of medications during pregnancy. We identified a cohort of pregnancies ending in live birth within the 2000–2007 Medicaid Analytic eXtract (MAX). Herein, we provide a blueprint to guide investigators who wish to create similar cohorts from healthcare utilization data and we describe the limitations in detail.

Methods

Among females ages 12–55, we identified pregnancies using delivery-related codes from healthcare utilization claims. We linked women with pregnancies to their offspring by state, Medicaid Case Number (family identifier) and delivery/birth dates. Then we removed inaccurate linkages and duplicate records and implemented cohort eligibility criteria (i.e., continuous and appropriate enrollment type, no private insurance, no restricted benefits) for claim information completeness.

Results

From 13,460,273 deliveries and 22,408,810 child observations, 6,107,572 pregnancies ending in live birth were available after linkage, cleaning, and removal of duplicate records. The percentage of linked deliveries varied greatly by state, from 0 to 96%. The cohort size was reduced to 1,248,875 pregnancies after requiring maternal eligibility criteria throughout pregnancy and to 1,173,280 pregnancies after further applying infant eligibility criteria. Ninety-one percent of women were dispensed at least one medication during pregnancy.

Conclusions

Mother-infant linkage is feasible and yields a large pregnancy cohort, although the size decreases with increasing eligibility requirements. MAX is a useful resource for studying medications in pregnancy and a spectrum of maternal and infant outcomes within the indigent population of women and their infants enrolled in Medicaid. It may also be used to study maternal characteristics, the impact of Medicaid policy, and healthcare utilization during pregnancy. However, careful attention to the limitations of these data is necessary to reduce biases.     

Intraspecific Variation in Home Range Overlap with Habitat Quality: A Comparison among Brown Bear Populations

We developed a conceptual model of spatial organization in vertebrates based upon changes in home range overlap with habitat quality. We tested the model using estimates of annual home ranges of adult females and densities for 30 populations of brown bears (Ursus arctos) in North America. We used seasonality as a surrogate of habitat quality, measured as the coefficient of variation among monthly actual evapotranspiration values for areas in which study populations were located. We calculated home range overlap for each population as the product of the average home range size for adult females and the estimated population density of adult females. Home range size varied positively with seasonality; however, home range overlap varied with seasonality in a nonlinear manner. Areas of low and high seasonality supported brown bears with considerable home range overlap, but areas of moderate seasonality supported brown bears with low home range overlap. These results are consistent with behavioural theory predicting a nonlinear relationship between food availability and territoriality.     

Twin seasonality in a rural Catalonian population

The seasonality of twinning in the Spanish populations has not been studied until now. Differences between seasonal distribution of the twin conceptions and those of the single births have been observed in other populations. The aim of this work is to explore the frequency of twinning in a rural population from Catalonia during the nineteenth century, as well as the seasonality patterns characterizing each of the twinning types. Data corresponding to all births recorded at Tortosa (South Catalonia) from 1801 to 1900 have been analyzed in order to study the twinning distribution. The distribution of the moving averages of the monthly rates of twins shows a peak in autumn. Twinning distribution differs from the total births' distribution in Tortosa. This fact is very clear in the case of unlike-sexed twins that have their greater incidence in the last quarter of the year, while the total maternities have their peak in the first one.     

Critical population size for fig/wasp mutualism in a seasonal environment: effect and evolution of the duration of female receptivity

Fig trees and their pollinating wasps form ca. 750 pairs of obligate mutualists, mainly in the tropics. Survival of each partner depends on that of its associated species. Here, we examine the possible outcome of such an interaction at small population size. Using phenology data collected on Ficus natalensis in Gabon, we modelled wasp survival and the reproductive success of the trees according to the duration of receptivity of the tree, the amplitude of flowering seasonality, and the size of the fig tree population. Since the duration of receptivity is critical in these population level models, we also determined the influence of individual selection on this phenological trait. The models give three major results: (1) The minimum fig population size required to sustain a wasp population increases with the amplitude of seasonality, and decreases with increasing duration of receptivity; (2) tree population reproductive success is higher when the duration of receptivity is longer and when the population is large, but (3) individual selection toward a long duration of receptivity is weak or absent.