Secondary Sex Ratio in Multiple Births

Twin Research and Human Genetics, 2006

Twin Research and Human Genetics, 2006

The temporal variation in the stillbirth rates (SBR), measured as the number of stillborn per 1000 total births, among singletons, twins and triplets was studied on Swedish birth data for the period 1869 to 2001 and comparisons with data from other populations were made. Among both single and multiple births there were marked, almost monotonously decreasing trends in the stillbirth rates. Among singletons the stillbirth rate decreased from 29.5 per 1000 in the period 1869 to 1878 to 3.4 in the period 1991 to 2001. Among twins the stillbirth rate decreased from 94 per 1000 in 1869 to 1878 to a minimum of 8.2 in 1991 to 2001 and among triplets from 166 per 1000 to a minimum of 19.8. The relative declining pattern in the SBRs was almost the same, being 88% among singletons, 91% among twins and 88% among triplets. In the 1980s and 1990s the definition of the stillbirth rate was changed in many countries, including Finland, but no changes in the definition of stillbirths have been made i...

Twin research and human genetics : the official journal of the International Society for Twin Studies, 2014

We analyzed the effect of total fertility rate (TFR) and crude birth rate (CBR) on the number of males per 100 females at birth, also called the secondary sex ratio (SR), and on the twinning rate (TWR). Earlier studies have noted regional variations in TWR and racial differences in the SR. Statistical analyses have shown that comparisons between SRs demand large data sets because random fluctuations in moderate data are marked. Consequently, reliable results presuppose national birth data. Here, we analyzed historical demographic data and their regional variations between counties in Sweden. We built spatial models for the TFR in 1860 and the CBR in 1751-1870, and as regressors we used geographical coordinates for the provincial capitals of the counties. For both variables, we obtained significant spatial variations, albeit of different patterns and power. The SR among the live-born in 1749-1869 and the TWR in 1751-1860 showed slight spatial variations. The influence of CBR and TFR ...

Early Human Development, 2015

The sex ratio (SR) at birth, also known as the secondary sex ratio, is defined as the number of males per 100 females and approximates 106. According to the literature, the SR shows notable heterogeneity and attempts have been made to identify factors influencing it, but comparisons demand large data sets. Attempts to identify associations between SRs and stillbirth rates (SBRs) have yielded inconsistent results. A common pattern observed in different countries is that during the first half of the twentieth century, the SR showed increasing trends, but during the second half, the trend decreased. Secular increases are thought to be caused by improved socioeconomic conditions. The recent downward trends have been attributed to new reproductive hazards. Similar findings have been made in the Nordic countries. Factors affecting the SR within families remain poorly understood. Although these factors have an effect on family data, they have not been identified in large

Acta Obstetricia et Gynecologica Scandinavica, 2000

Background. The high maternal mortality levels in today's developing countries were also found throughout the history of currently affluent countries. The parish information system in Sweden offers unique possibilities for research in historical cohorts. Furthermore, vital events surveillance systems are scarce in today's developing countries. Methods. This cohort study covers 42,387 mothers who gave birth to 150,932 infants during the 19th century in the Skellefteå and Sundsvall areas. Among these women, 1 237 were dead within one year after delivery. The analysis of the cause of these deaths was done according to the various ICD definitions. Parity five and above was defined as grand multiparity. Results. Maternal mortality ratios, deaths per 100,000 live births were as follows: 256.4 (direct obstetric deaths), 320.7 (direct and indirect obstetric deaths), 489.2 (pregnancy-related deaths), 347.8 (late maternal deaths) and 837.0 (maternal deaths and late maternal deaths). In this study, 59% of all maternal deaths occur within the first 42 days of delivery, two thirds of them having direct and indirect obstetric causes. Of the late maternal deaths, the bulk were infectious or other indirect deaths, mirroring more general female mortality and the preexistent endemic situation of tuberculosis and other infectious diseases. The combination of previous stillbirth and infant death represented the highest risk ratios, RR 2.77-3.62, while grand multiparity was not associated with increased risk. Urbanized and industrialized areas tended to have higher maternal mortality. Conclusions. In conclusion, this study shows that the mother's reproductive history was the most important risk factor measured for all definitions of maternal death. Grand multiparity did not increase the risk of maternal death. Maternal mortality ratio varied threefold in the study population, depending on the definition used. The high mortality ratios found in this study, only declining by the end of the century, should be interpreted as a general condition of the society since no significant differences could be perceived regarding social class, while unmarried women were more at risk.

Asian Journal of Probability and Statistics, 2018

The sex ratio (SR) is usually defined as the number of males per 100 females within an area or, as in this study, the proportion of males among all births (P M). It has been observed that among newborns, there is typically a slight excess number for boys compared to girls. Consequently, the SR becomes greater than 100, which is around 106 in number, and the chance of new born males is around 0.515. Attempts have been made to identify the factors those are influencing the level of the P M. Previous researches stated that where prenatal losses are low, as in the Western countries, the SRs are also become high around 105 to 106, but in areas where the frequencies of prenatal losses are relatively high then the SRs are found to be low around 102. Later on several researches have focused on temporal, regional and seasonal fluctuations of SR. In general, factors that affect the SR within the families remain poorly understood. Attempts to identify such factors in national birth registers are also remained to be unsuccessful. Recently, SR studies have mainly concentrated on the identification of general but occasional factors. In this study, we tried to identify the effects of issues like maternal age and type of delivery (live-and stillborn, singletons and multiples) to identify the controlling parameters of sex ratio during birth. Post experimental outcome showed that there is no significant difference between live-and stillborn and maternal age had as no significant effect for controlling sex ratio. The SR is higher among singletons than that of multiples, but there is no significant difference obtained in SR between twins and triplets. Among singletons the temporal differences are non-significant, but for twins and triplets, significant temporal differences were obtained.

Biodemography and Social Biology, 2011

Journal of Epidemiology & Community Health, 2000

Study objective-To identify variables available in early Swedish delivery records and their relation to birth outcomes for home and hospital deliveries in Gothenburg at the early part of this century. Design-A retrospective recovery of original delivery records and social variables in a cross sectional population. Setting-Gothenburg, Sweden. Participants-851 fullterm singleton female births with known gestational age born into five birth cohorts on selected dates (1908, 1914, 1918, 1922 and 1930). Main results-Delivery site, maternal parity, gestational age, and social group were significant factors influencing birth outcome as birth weight and length. The mean birth weight and length of hospital born infants was consistently lower than for home deliveries across all cohorts. Site of delivery changed significantly during the period of births under study, 1908-1930. Conclusions-In this study, which was based on original delivery records from the early part of this century, it was found that delivery site was an important factor influencing birth outcome across five birth cohorts. Utilisation of delivery services changed during the period of study. Thus, to avoid selection bias, the application of delivery records should reflect the birthing practice of the time period in question.

Twin Research and Human Genetics, 2009

The History of the Family, 2006

This study investigates differentials in the decline of cause-specific infant mortality by marital status of the mother in Stockholm (1878-1925) and factors contributing to the explanation of these differentials using computerized records of individual entries from the Roteman Archives. Included in the analysis were 120,094 children less than 1 year of age who lived in Södermalm during this period. Cause-specific mortality rates were calculated for three time periods. Cox's regression analysis was used to study the relationship between overall and cause-specific risk of infant death and of being born in and out of wedlock in relation to a set of variables. Infant mortality rates and mortality risks were higher among children born out of rather than in wedlock. The most pronounced differentials in cause-specific mortality rates between these groups of children were seen in cases of diarrhea. The socioeconomic status of the household head and number of children in the household were statistically significant with infant mortality, but explain only part of the excess mortality risk of children born out of wedlock. In Stockholm at the turn of the 19th century being born out of wedlock was strongly associated with poor health outcomes, particularly in diarrheal diseases, pneumonia/bronchitis, and immaturity/congenital causes.