Assisted reproductive technologies (ARTs) such as in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI) are still discussed critically, as there is no consensus on whether these treatments could be the cause of risk factors for obstetric problems such as breech presentation. The aim of this study was to test the association between ART and breech presentation among 11920 singleton term births taking place in Vienna from 2010 to 2020. In this single-centre medical record-based study, data concerning the conception mode (spontaneous versus IVF or ICSI), child presentation, birth mode, newborn sex and size as well as age, height, weight, and reproductive history of the mother were included. Three hundred twenty-six newborns (2.7%) were conceived by IVF or ICSI, and 527 newborns (4.4%) were delivered in breech presentation. Breech presentation occurred in 7.6% of IVF/ICSI children but only in 4.3% of spontaneously conceived children (P = 0.019). ART increased the crude risk of breech presentation significantly (OR = 1.67; 95% CI 1.71 – 2.38). After adjusting for maternal age, height, number of previous births, smoking, and newborn sex, however, ART had no longer a significant impact on the risk of breech presentation. In contrast, breech presentation was significantly associated with higher maternal age as well as a lower number of previous births, but not with ART. This study shows that the adverse outcomes of IVF and ICSI pregnancies may not be due to the ART treatment alone but might also be due to the mostly higher age and lower parity of the mothers using ART.

Over the previous decades, twinning rates worldwide have increased remarkably. This study aimed to describe changes in multiple birth rates and related demographic characteristics, such as maternal age and the level of education of parents in South Korea from 1981 to 2019. This study analyzed birth data obtained from the Korean Statistical Information Service. From 1981 to 2019, the total twinning rate increased from 5 to 22.5 pairs per 1000 births. This rapid increase was due to an increase in dizygotic twin births, which mainly occurred in mothers aged between 30 and 39 years. The average maternal age of multiples increased from 26.06 years in 1981 to 33.98 years in 2019, suggesting that a delay in childbearing contributed to the increase in the twinning rate. The percentage of mothers of multiples who completed a college or higher degree (CHD) increased by 1000% from 1981 to 2019, indicating that a sharp increase in the level of education of females in part explains the delay in childbearing. The percentages of individuals who completed a CHD were higher among parents of multiples than among those of singletons in recent years when public funding arrangements for fertility treatments were available. This result suggested that completion of higher education may be associated with increased use of assisted reproductive technology (ART) independent of the financial status of couples. Taken together, the analysis suggested that increased maternal age, ART and the increased number of females who completed CHD may be responsible for the remarkable increase in the rates of multiple births in South Korea in the last four decades.

Maternal age is a significant factor influencing in vitro fertilization (IVF) outcomes. Oxidative stress (OS) is one of the major causes of age-related cellular and molecular damage. The purpose of this work was to investigate the correlation between maternal age with intrafollicular antioxidants and OS markers in follicular fluid (FF), and also to determine the OS status in patients of advanced age. This study was a prospective study including 201 women undergoing IVF whose age was between 24 and 45 years old. FF samples were obtained from mature follicles at the time of oocyte retrieval. After treatment of FF, lipid peroxidation levels (MDA) and enzyme activities such as superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione (GSH) level were evaluated using spectrophotometry. The results indicated that the age cutoff point for increasing the MDA level was fixed at 37 years, allowing the study to be differentiated into two age groups. Group I included patients whose age was less than 37 years, and group II included patients whose age was greater than or equal 37 years. Statistical analysis revealed that MDA and GSH levels and GR activity were significantly higher in group II compared with group I. The SOD and CAT activities were significantly less in group II compared with group I. We concluded that from 37 years old a reproductive ageing was accompanied by a change in the antioxidant pattern in FF that impaired reactive oxygen species scavenging efficiency.

In the 19th century, a series of international statistical congresses began that were important for population studies, including twin research. The introduction of common rules for the national demographic registers enabled scientists to contribute to the genesis of statistical research. The congress in St. Petersburg in 1872, in particular, focused on the movements of the population, and how they should be registered. Among the facts to be recorded were in multiple births, the sex and number of children born alive or still-born, whether legitimate or illegitimate, and the age of the mother at the date of the births. During the history of twin research, Hellin's law has played a central role because it is an approximately correct association between the rates of multiple maternities. It has been mathematically proven that Hellin's law does not hold as a general rule. Analyses show divergences from the law that are difficult to explain and/or eliminate. Varying improvements of this law have been proposed. The majority of all studies of Hellin's law are based on empirical rates of multiple maternities, ignoring random errors. Such studies can never confirm the law, but only identify errors with respect to Hellin's law that are too large to be characterized as random. It is of particular interest to note and explain why the rates of higher multiple maternities are sometimes too high or too low when Hellin's law is used as a benchmark. Studies have shown that there were investigators before Hellin who have contributed substantially to Hellin's law. In this article, we re-examine some old data sets and contributions in which Hellin's law has been evaluated and also analyze recent data.

The present study investigates the twinning rates in the city of São Paulo, Brazil, during the years 2003–2014. The data were drawn from the Brazilian Health Department database of Sistema de Informações de Nascidos Vivos de São Paulo—SINASC (Live Births Information System of São Paulo). In general, more information is available on the incidence of twinning in developed countries than in developing ones. A total of 24,589 twin deliveries and 736 multiple deliveries were registered in 140 hospitals of São Paulo out of a total of 2,056,016 deliveries during the studied time period. The overall average rates of singleton, twin, and multiple births per 1,000 maternities (‰) were 987.43, 11.96 (dizygotic (DZ) rate was 7.15 and monozygotic (MZ) 4.42), and 0.36, respectively. We further regressed maternal age and historical time period on percentage of singleton, twin, and multiple birth rates. Our results indicated that maternal age strongly positively predicted twin and multiple birth rates, and negatively predicted singleton birth rates. The historical time period also positively, although weakly, predicted twin birth rates, and had no effect on singleton or multiple birth rates. Further, after applying Weinberg's differential method, we computed regressions separately for the estimated frequencies of DZ and MZ twin rates. DZ twinning was strongly positively predicted by maternal age and, to a smaller degree, by time period, while MZ twinning increased marginally only with higher maternal age. Factors such as increasing body mass index or air pollution can lead to the slight historical increase in DZ twinning rates. Importantly, consistent with previous cross-cultural and historical research, our results support the existence of an age-dependent physiological mechanism that leads to a strong increase in twinning and multiple births, but not singleton births, among mothers of higher age categories. From the ultimate perspective, twinning and multiple births in later age can lead to higher individual reproductive success near the end of the reproductive career of the mother.

In this study, the temporal trends in the rates of multiple maternities in Denmark were analyzed and an association between the rates of multiple maternities and the socioeconomic variations in Denmark was obtained. The findings are compared with the results obtained in studies of Swedish rates. Obtained temporal differences in the twinning rates (TWRs) were similar to the results presented by Fellman and Eriksson (2014). Temporal variation in rates of multiple maternities in Sweden (1751–2000). JP Journal of Biostatistics, 11, 2, 143–156.

The development and life performance of 404 high-producing Holstein dairy cows was studied from birth onwards and during two lactations. The management, environment and parental genetics of the cows were known in detail. Cluster analysis identified four performance ‘types’: high-yielding (HY) cows and persistently high-yielding (PHY) cows, which accounted for 33% of the animals; medium-yielding (MY) cows, 41%; and low-yielding (LY) cows, 26%. Prenatal determinants of the life performance of the progeny were analyzed. Developmental and environmental factors were excluded as determinants of performance (including birth weight, level of passive immunity transfer, growth rate, age at first parturition and reproductive efficiency). Life performance did show minor seasonal effects, with more HY cows but less PHY being born during the cold season (90.1% in HY; 58.3% in PHY v. 81.5%). Instead, the single most important factor influencing life performance of daughters was maternal age. HY cows were born from the youngest mothers (1.89±1.14 parturitions, 3.12±1.42-year old), whereas LY cows were born from the oldest (2.72±1.80 parturitions, 3.97±2.01-year old; P<0.001). Life performance of the dams did not differ among clusters. In addition, metabolic parameters (fat and protein yield) were found to correlate significantly with yields between the first and second lactations (milk yield: r=0.357; fat yield: r=0.211; protein yield: r=0.277; P<0.0001), suggesting the influence of the individual. These results suggest that under optimal health, nutritional and environmental conditions, maternal aging is an important determinant of the life performance of progeny and argue for the need to identify conditions that contribute to health and disease in progeny according to the Developmental Origin of Health and Disease or DOHaD concept. Our findings may help the development of novel management guidelines for dairy farms.

Recently, there has been a significant increase in the rate of multiple births in most developed countries. However, few population-based studies have been conducted in China regarding the epidemiology of twin births in recent years. We performed a descriptive analysis of twin births from 1993 to 2005 using data from a population-based perinatal care program in southeast China. The twin birth rate in southeast China was 0.65%, and the twin birth rates from 1993 to 2005 fluctuated between 0.60% and 0.70%. During the three periods of 1993–1996, 1997–2000, and 2001–2005, the twin birth rate increased from 0.57% to 0.71% in urban areas (p = .005) and from 0.59% to 0.68% in mothers who had an education level of high school or higher (p = .046). After 2000, the twin birth rate of primiparae 30 years of age and older significantly increased from 0.72% to greater than 1.20%. We concluded that the twin birth rates in southeast China from 1993 to 2005 stayed constant in the overall population but increased in certain subgroups of women, presumably due to increased use of fertility treatment and the development of assisted reproductive technology.

The infant mortality rate (IMR) among single and twin births from 1999 to 2008 was analyzed using Japanese Vital Statistics. The IMR was 5.3-fold higher in twins than in singletons in 1999 and decreased to 3.9-fold in 2008. The reduced risk of infant mortality in twins relative to singletons may be related, partially, to survival rates, which improved after fetoscopic laser photocoagulation for twin — twin transfusion syndrome. The proportion of neonatal deaths among total infant deaths was 54% for singletons and 74% for twins. Thus, intensive care of single and twin births may be very important during the first month of life to reduce the IMR. The IMR decreased as gestational age (GA) rose in singletons, whereas the IMR in twins decreased as GA rose until 37 weeks and increased thereafter. The IMR was significantly higher in twins than in singletons from the shortest GA (<24 weeks) to 28 weeks as well as ≥38 weeks, whereas the IMR was significantly higher in singletons than in twins from 30 to 36 weeks. As for maternal age, the early neonatal and neonatal mortality rates as well as the IMR in singletons were significantly higher in the youngest maternal age group than in the oldest one, whereas the opposite result was obtained in twins. The lowest IMR in singletons was 1.1 per 1,000 live births for ≥38 weeks of gestation and heaviest birth weight (≥2,000 g), while the lowest IMR in twins was 1.8 at 37 weeks and ≥2,000 g.

Age at entry to motherhood is increasingly socially polarised in the UK. Early childbearing typically occurs among women from disadvantaged backgrounds relative to women with later first births. The Millennium Cohort finds differentials in their children's development, cognitive and behavioural, at age 5, by mother's age. These could be due to difficulties facing immature mothers, but much of it is attributable to young mothers’ social origins, or inequalities apparent at the age 0 survey, which may also have had earlier origins. The developmental penalty left to be attributed to the mother's age per se is, at most, modest.

Using the South Korean national live birth data for the years 2003 to 2007, monozygotic (MZ) and dizygotic (DZ) twin birth rates were estimated and analyzed by maternal age, and parents of twins and those of singletons were compared in their level of education. During this period, while the MZ twin birth rate showed no change, the DZ twin birth rate increased up to 9.4 pairs per thousand births. This rate is close to five times as high as the natural DZ twinning rate in the South Korean population. The highest twinning rate occurred among mothers aged 30 to 34 years, followed by mothers aged 25 to 29. These results represented the first evidence for the downward trend in ages of mothers of twins. In each year between 2003 and 2006, percentages of parents who completed college or higher level of education were higher in the twin than in the singleton group, suggesting that the parental socioeconomic level became higher in twins than in singletons. We speculated that these demographic changes occurred because assisted reproductive technology was more easily available among parents of high socioeconomic status. In their sampling strategies, twin researchers should consider our findings of recent changes in demographic characteristics of parents of twins as well as increased DZ twin birth rates.

We analyzed the characteristics of weight growth and present the weight growth charts from birth to 6 years of age in Japanese triplets. The study included 366 mothers and their 1098 triplet children, who were born between 1978 and 2006. Data were collected through a mailed questionnaire sent to the mothers asking for information recorded in medical records. For these births, data on triplets' weight growth, gestational age, sex, parity, and maternal age at delivery were obtained from records in the Maternal and Child Health Handbooks, which is provided by the authorities after a report of pregnancy. Birthweight proved to be the strongest contribution on weight of triplets from 1 to 6 years of age. In addition, gestational age was also a significant contributing factor to weight from birth to 6 years of age. Moreover, males had a higher weight from birth to 6 years of age than females. Compared to the 50th percentile of the growth standard for the general population of Japan, the weight deficit of the triplets was more than 40% at birth (male, –1.28 kg; female, –1.28 kg), decreased within the first 1 year of age, and fluctuated between 4% and 9% until 6 years of age (male, –1.82 kg; female, –1.78 kg). In conclusion, triplets have lower birth weight than singletons and in spite of the rapid catch-up growth during first year of life they are behind singletons even in mid-childhood. This study provides growth curves for use in triplets.

The aims of the present study were to evaluate the contribution of the genetic and environmental factors to the risk of teenage childbearing, and to study whether life style, socio-economic conditions, and personality traits could explain possible familial effects. We linked two population-based registers: the Swedish Twin Register and the Swedish Medical Birth Register. The study covers female twin pairs born between 1953 and 1958, having their first infant before the age of 30 years (n = 1885). In order to separate familial effects from other environmental influences, and genetic effects from shared environmental effects, only complete twin pairs with known zygosity were included, in all 260 monozygotic and 370 dizygotic twin pairs. We used quantitative genetic analyses to evaluate the importance of genetic and environmental effects for liability to teenage childbearing. Logistic regression analyses were used to estimate the effects of life style, socio-economic situation, and personality on the probability of teenage childbearing, and to study whether psychosocial factors could explain possible familial effects. Fifty-nine percent (0–76%) of the variance in being a teenage mother was attributable to heritable factors; 0% (0–49%) was due to shared environmental factors; and 41% (23–67%) was explained by non-shared environmental factors. Thus, the data were consistent with the hypothesis that the familial aggregation of teenage childbearing is completely explained by genetic factors, although the alternative hypothesis that familial aggregation is entirely explained by shared environmental factors cannot be ruled out. Significant effects of smoking habits, housing conditions, and educational level were found in relation to liability to teenage childbearing. However, the familial effects on risk of teenage childbearing were not mediated through similarities in life style and socio-economic factors. When studying risk factors for teenage childbearing, it is recommended to include life style and socio-economic variables as well as information about family history of teenage childbearing. Twin Research (2000) 3, 23–27.