The Long-Term Cognitive and Socioeconomic Consequences of Birth Intervals: A Within-Family Sibling Comparison Using Swedish Register Data

Birth Spacing and Parents' Physical and Mental Health: An Analysis Using Individual and Sibling Fixed Effects

An extensive literature has examined the relationship between birth spacing and subsequent health outcomes for parents, particularly for mothers. However, this research has drawn almost exclusively on observational research designs, and almost all studies have been limited to adjusting for observable factors that could confound the relationship between birth spacing and health outcomes. In this study, we use Norwegian register data to examine the relationship between birth spacing and the number of general practitioner consultations for mothers' and fathers' physical and mental health concerns immediately after childbirth (1-5 and 6-11 months after childbirth), in the medium term (5-6 years after childbearing), and in the long term (10-11 years after childbearing). To examine short-term health outcomes, we estimate individual fixed-effects models: we hold constant factors that could influence parents' birth spacing behavior and their health, comparing health outcomes after different births to the same parent. We apply sibling fixed effects in our analysis of medium- and long-term outcomes, holding constant mothers' and fathers' family backgrounds. The results from our analyses that do not apply individual or sibling fixed effects are consistent with much of the previous literature: shorter and longer birth intervals are associated with worse health outcomes than birth intervals of approximately 2-3 years. Estimates from individual fixed-effects models suggest that particularly short intervals have a modest negative effect on maternal mental health in the short term, with more ambiguous evidence that particularly short or long intervals might modestly influence short-, medium-, and long-term physical health outcomes. Overall, these results are consistent with small to negligible effects of birth spacing behavior on (non-pregnancy-related) parental health outcomes.

Interpregnancy interval and maternal and neonatal morbidity: a nationwide cohort study

This study aimed to assess the association between interpregnancy interval (IPI)-the time from childbirth to conception of the next pregnancy-and maternal and neonatal morbidity. The World Health Organization (WHO) currently recommends an IPI of at least 24 months after a live birth to reduce adverse birth outcomes. However, assessing the relationship between IPI and perinatal outcome is complicated by confounding factors. We conducted a nationwide population-based cohort study using Swedish registry data, allowing for adjustment of maternal characteristics and health at first birth. The study population consisted of all women with a singleton, live, and vaginal first birth with a second singleton birth within five years during 1997-2017, covering 327,912 women and 655,824 neonates. IPI was grouped into six-month intervals with 24-29 months as the reference. The association between IPI and morbidity was examined using multivariate logistic regression. For women having a vaginal delivery at their first birth, intervals < 24-29 months were associated with decreased maternal morbidity and unaffected neonatal morbidity. Intervals > 24-29 months were associated with increased maternal and neonatal morbidity. Our findings question the relevance of WHO's recommendation of an IPI of at least 24 months in a high-income country.

Short birth interval and associated factors in rural India: A cross-sectional study

Short Birth Interval (SBI) is one of the main causes of adverse maternal and child health outcomes. A 33-month birth-to-birth interval between two successive live births should be followed to minimize the risk of adverse maternal and child health. This study aimed to examine the prevalence of SBI and the associated factors in rural India. Information on 98,522 rural mothers from the fourth round of National Family Health Survey data was analyzed. Bivariate statistics, logistic regression, Moran's I, and Cluster and Outlier Analysis have been used to assess the prevalence and spatial pattern of SBI in rural India. Results revealed that about half of the mothers in rural India had experienced SBI. Rural Indian mothers whose child was not alive (OR = 1.76, 95% CI = 1.63-1.90), were not using any contraceptive methods (OR = 1.42, 95 % CI = 1.37-1.48) and not breastfeeding (OR = 2.73, 95% CI = 2.50-2.97) were more likely to experience SBI. On the other hand, rural mothers from the middle, richer and richest wealth quintiles (OR = 0.91, 95% CI = 0.86-0.97; OR = 0.84, 95% CI = 0.80-0.92; OR = 0.60, 95% CI = 0.55-0.66) and of age over 30 years (OR = 0.38., 95% CI = 0.36-0.39) were less likely to experience SBI. Analysis of spatial patterns revealed clear east-west differences in the prevalence of SBI. There was strong clustering of high values of SBI in most districts across the central, northern, western, and southern regions. The study suggests the need to introduce appropriate interventions and programs focused on reducing the prevalence of SBI in rural India.

Using age difference and sex similarity to detect evidence of sibling influence on criminal offending

BACKGROUND

Sibling resemblance in crime may be due to genetic relatedness, shared environment, and/or the interpersonal influence of siblings on each other. This latter process can be understood as a type of 'peer effect' in that it is based on social learning between individuals occupying the same status in the social system (family). Building on prior research, we hypothesized that sibling pairs that resemble peer relationships the most, i.e., same-sex siblings close in age, exhibit the most sibling resemblance in crime.

METHODS

Drawing on administrative microdata covering Finnish children born in 1985-97, we examined 213 911 sibling pairs, observing the recorded criminality of each sibling between ages 11 and 20. We estimated multivariate regression models controlling for individual and family characteristics, and employed fixed-effects models to analyze the temporal co-occurrence of sibling delinquency.

RESULTS

Among younger siblings with a criminal older sibling, the adjusted prevalence estimates of criminal offending decreased from 32 to 25% as the age differences increased from less than 13 months to 25-28 months. The prevalence leveled off at 23% when age difference reached 37-40 months or more. These effects were statistically significant only among same-sex sibling pairs (p < 0.001), with clear evidence of contemporaneous offending among siblings with minimal age difference.

CONCLUSIONS

Same-sex siblings very close in age stand out as having the highest sibling resemblance in crime. This finding suggests that a meaningful share of sibling similarity in criminal offending is due to a process akin to peer influence, typically flowing from the older to the younger sibling.

Birth Spacing and Health and Socioeconomic Outcomes Across the Life Course: Evidence From the Utah Population Database

The relationship between birth interval length and child outcomes has received increased attention in recent years, but few studies have examined offspring outcomes across the life course in North America. We use data from the Utah Population Database to examine the relationship between birth intervals and short- and long-term outcomes: preterm birth, low birth weight (LBW), infant mortality, college degree attainment, occupational status, and adult mortality. Using linear regression, linear probability models, and survival analysis, we compare results from models with and without sibling comparisons. Children born after a birth interval of 9-12 months have a higher probability of LBW, preterm birth, and infant mortality both with and without sibling comparisons; longer intervals are associated with a lower probability of these outcomes. Short intervals before the birth of the next youngest sibling are also associated with LBW, preterm birth, and infant mortality both with and without sibling comparisons. This pattern raises concerns that the sibling comparison models do not fully adjust for within-family factors predicting both spacing and perinatal outcomes. In sibling comparison analyses considering long-term outcomes, not even the very shortest birth intervals are negatively associated with educational or occupational outcomes or with long-term mortality. These findings suggest that extremely short birth intervals may increase the probability of poor perinatal outcomes but that any such disadvantages disappear over the extended life course.

In Their Footsteps or Shadow? Gender Differences in Choosing a STEM Major as a Function of Sibling Configuration and Older Sibling’s Gender and Math Ability

Although the association between siblings’ compositional characteristics and educational performance has been extensively studied, the question of whether the features of a sibling group are related to substantive gendered educational preferences has not been examined. Our analysis of the National Longitudinal Survey of Youth 1979 cohort (NLSY-79) Mothers and Children Files (N = 1545; 57% young women; 22% STEM major) showed that siblings’ compositional characteristics matter for STEM major preferences in college, but only for young women. Our findings indicated that women were more likely to prefer a STEM major if they were raised in smaller sibling groups, in male sibling group dominance, and if they had an older sister with high math achievement. These results are in line with the resource dilution approach; they shed light on the effects of being in a normative male-role sibling group climate; and they suggest that gendered outcomes are shaped by the interplay of role modeling and same-gender competitive stimulation. We also found that for young men, their preference for majoring in a STEM field was mostly driven by their own math ability. These findings suggest that socialization experiences that operate on the sibling level play a crucial role in whether girls become interested in and pursue “gender-atypical” educational choices. Our findings also underscore the need to differentiate these theoretical approaches by gender, particularly when applied to gendered outcomes such as STEM career trajectories.

Birth Spacing and Fertility in the Presence of Son Preference and Sex-Selective Abortions: India's Experience Over Four Decades

Since the advent of prenatal sex-determination technologies in the mid-1980s, India has experienced an increasingly male-biased sex ratio at birth, presumably from sex-selective abortions. Abortions lengthen birth intervals, but we know little about how birth spacing has changed or the effects of these changes. I show that, although the overall length of birth intervals increased from 1970 to the mid-2010s, well-educated women with no sons had the most substantial lengthening, as well as the most male-biased sex ratios. Furthermore, most of these changes took place immediately after the introduction of prenatal sex-determination technologies. Consequently, some women without sons now have longer birth intervals than those with sons, reversing India's traditional spacing pattern. Women with low education continue short birth spacing when they have no sons, with only limited evidence of male-biased sex ratios. Because of the rapid lengthening of birth intervals, period fertility rates substantially overestimated how fast cohort fertility fell. Moreover, predicted cohort fertility is still 10%-20% above the period fertility rate. If the lengthening of birth intervals arises from repeated abortions, the associated short pregnancy spacing may counteract any positive effects of longer birth spacing. There is, however, no evidence of this effect on infant mortality. Judging from sex ratios, sex-selective abortion use is not declining.

Iron status in mid-pregnancy and associations with interpregnancy interval, hormonal contraceptives, dietary factors and supplement use

Adequate iron supply in pregnancy is important for both the woman and the fetus, but iron status is often assessed late in first trimester, if assessed at all. Therefore, identification of factors associated with iron status is important to target vulnerable groups with increased risk of deficiency. Our objectives were to (1) describe iron status in mid-pregnancy and (2) identify sociodemographic and lifestyle predictors of pregnancy iron status. This cross-sectional study uses data from The Norwegian Mother, Father and Child Cohort Study (collected 2002-2008) and The Medical Birth Registry of Norway. Iron status was measured as non-fasting plasma ferritin (P-Fe) and transferrin in gestational week (GW) 18 (n 2990), and by lowest reported Hb in GW 0-30 (n 39 322). We explored predictors of iron status with elastic net, linear and log-binomial regression models. Median P-Fe was 33 μg/l, and 14 % had depleted iron stores (P-Fe <15 μg/l). P-Fe below 30 μg/l was associated with reduced Hb. We identified eleven predictors, with interpregnancy interval (IPI) and parity among the most important. Depleted iron stores was more common among women with IPI < 6 months (56 %) and 6-11 months (33 %) than among those with IPI 24-59 months (19 %) and among nulliparous women (5 %). Positively associated factors with iron status included hormonal contraceptives, age, BMI, smoking, meat consumption and multi-supplement use. Our results highlight the importance of ferritin measurements in women of childbearing age, especially among women not using hormonal contraceptives and women with previous and recent childbirths.

When and Where Birth Spacing Matters for Child Survival: An International Comparison Using the DHS

A large body of research has found an association between short birth intervals and the risk of infant mortality in developing countries, but recent work on other perinatal outcomes from highly developed countries has called these claims into question, arguing that previous studies have failed to adequately control for unobserved heterogeneity. Our study addresses this issue by estimating within-family models on a sample of 4.5 million births from 77 countries at various levels of development. We show that after unobserved maternal heterogeneity is controlled for, intervals shorter than 36 months substantially increase the probability of infant death. However, the importance of birth intervals as a determinant of infant mortality varies inversely with maternal education and the strength of the relationship varies regionally. Finally, we demonstrate that the mortality-reducing effects of longer birth intervals are strong at low levels of development but decline steadily toward zero at higher levels of development. These findings offer a clear way to reconcile previous research showing that birth intervals are important for perinatal outcomes in low-income countries but are much less consequential in high-income settings.

Interpregnancy intervals and perinatal and child health in Sweden: A comparison within families and across social groups

A large body of research has shown that children born after especially short or long birth intervals experience an elevated risk of poor perinatal outcomes, but recent work suggests this may be explained by confounding by unobserved family characteristics. We use Swedish population data on cohorts born 1981-2010 and sibling fixed effects to examine whether the length of the birth interval preceding the index child influences the risk of preterm birth, low birth weight, and hospitalization during childhood. We also present analyses stratified by salient social characteristics, such as maternal educational level and maternal country of birth. We find few effects of birth intervals on our outcomes, except for very short intervals (less than seven months) and very long intervals (>60 months). We find few differences in the patterns by maternal educational level or maternal country of origin after stratifying by the mother's highest educational attainment.

Time and Generation: Parents' Integration and Children's School Performance in Sweden, 1989-2011

A central element of assimilation theory is that increasing time and number of previous immigrant generations in a host country leaves immigrants and their children more integrated and capable of navigating the host society. However, the underperformance of some immigrant groups in Sweden calls into question this relationship. Additionally, many studies regard intermarriage as an outcome of immigrant integration and rarely investigate whether integration continues after intermarriage. Using population level data from the Swedish interdisciplinary panel on 22 cohorts of ninth-grade students born between 1973 and 1995, we examine the effect of parents' time in Sweden on their children's grade point average using family fixed effects. Additionally, we investigate whether this relationship differs between "2.0" and "2.5" generation children. We find, generally, that parents' time in Sweden increases their children's educational performance, though some variation by parents' region of origin exists. This supports the idea that integration experiences in immigrant families can be transmitted across generations. Further, this generally holds for both the 2.0 and 2.5 generation children. This relationship among the 2.5 generation is notable as previous studies using a family-based approach looking at the intergenerational transmission of integration have largely focused on the children of two foreign-born parents.

Birth Intervals and Health in Adulthood: A Comparison of Siblings Using Swedish Register Data

A growing body of research has examined whether birth intervals influence perinatal outcomes and child health as well as long-term educational and socioeconomic outcomes. To date, however, very little research has examined whether birth spacing influences long-term health. We use contemporary Swedish population register data to examine the relationship between birth-to-birth intervals and a variety of health outcomes in adulthood: for men, height, physical fitness, and the probability of falling into different body mass index categories; and for men and women, mortality. In models that do not adjust carefully for family background, we find that short and long birth intervals are clearly associated with height, physical fitness, being overweight or obese, and mortality. However, after carefully adjusting for family background using a within-family sibling comparison design, we find that birth spacing is generally not associated with long-term health, although we find that men born after very long birth intervals have a higher probability of being overweight or obese in early adulthood. Overall, we conclude that birth intervals have little independent effect on long-term health outcomes.