Comparison of birth weight between school health records and medical birth records in Denmark: determinants of discrepancies

Childhood body mass index and the subsequent risk of anorexia nervosa and bulimia nervosa among women: A large Danish population-based study

OBJECTIVE

Evidence linking childhood body mass index (BMI) with subsequent eating disorders is equivocal. Potential explanations include different study populations and size, and that anorexia nervosa (AN) and bulimia nervosa (BN) should be studied separately. We examined whether birthweight and childhood BMI were associated with subsequent risk of AN and BN in girls.

METHOD

We included 68,793 girls from the Copenhagen School Health Records Register born between 1960 and 1996 with information on birthweight and measured weights and heights obtained from school health examinations at ages 6-15 years. Diagnoses of AN and BN were retrieved from Danish nationwide patient registers. We used Cox proportional hazards regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

We identified 355 cases of AN (median age: 19.0) and 273 cases of BN (median age: 21.8). Higher childhood BMI was linearly associated with decreasing risk of AN and increasing risk of BN at all childhood ages. At age 6, the HR for AN was 0.85 (95% CI: 0.74-0.97) per BMI z-score and the HR for BN was 1.78 (95% CI: 1.50-2.11) per BMI z-score. Birthweight >3.75 kg was associated with increased risk of BN compared to a birthweight of 3.26-3.75 kg.

CONCLUSION

Higher BMI in girls at ages 6-15 years was associated with decreasing risk of AN and increasing risk of BN. Premorbid BMI could be relevant for the etiology of AN and BN, and in identifying high risk individuals.

PUBLIC SIGNIFICANCE

Eating disorders are associated with elevated mortality, especially AN. Using a cohort of Copenhagen school children, we linked information on BMI at ages 6-15 years for 68,793 girls with nationwide patient registers. Low childhood BMI was associated with increased risk of AN, whereas high childhood BMI was associated with increased risk of BN. These findings may assist clinicians in identifying individuals at high-risk of these diseases.

Birth weight, childhood body mass index, and risk of diverticular disease in adulthood

OBJECTIVE

Adult overweight is associated with increased risk of diverticular disease (DD). We investigated associations between birthweight and childhood body mass index (BMI) and DD.

METHODS

Cohort study of 346,586 persons born during 1930-1996 with records in the Copenhagen School Health Records Register. Data included birthweight, and height and weight from ages 7 through 13. We used Cox proportional hazard regression to examine associations between birthweight and BMI z-scores and DD registered in the Danish National Patient Registry. Due to non-proportionality, we followed participants from age 18-49 and from age 50.

RESULTS

During follow-up, 5459 (3.2%) women and 4429 (2.5%) men had DD. For low and high BMI in childhood, we observed a higher risk of DD before age 50. Among women with z-scores <0 at age 13, the hazard ratio (HR) was 1.16 [95% confidence interval (CI): 0.98-1.39] per one-point lower z-score. For z-scores ≥0 at age 13, the HR was 1.30 (95% CI: 1.11-1.51) per one-point higher z-score. Among men with z-scores <0 at age 13, the HR was 1.02 (95% CI: 0.85-1.22). For z-scores ≥0 at age 13, the HR was 1.54 (95% CI: 1.34-1.78). Z-scores ≥0 were not associated with DD after age 50. Among women only, birthweight was inversely associated with DD before age 50 [HR = 0.90 (95% CI: 0.83-0.99) per 500 g higher birthweight].

CONCLUSION

BMI z-scores below and above zero in childhood were associated with higher risk of DD before age 50. In addition, we observed lower risk of DD among women, the higher their birthweight.

Validation of birth certificate and maternal recall of events in labor and delivery with medical records in the Iowa health in pregnancy study

Background

Epidemiological research of events related to labor and delivery frequently uses maternal interview or birth certificates as a primary method of data collection; however, the validity of these data are rarely confirmed. This study aimed to examine the validity of birth certificate data and maternal interview of maternal demographics and events related to labor and delivery with data abstracted from medical records in a US setting.

Methods

Birth certificate and maternal recall data from the Iowa Health in Pregnancy Study (IHIPS), a population-based case-control study of risk factors for preterm and small-for-gestational age births, were linked to medical record data to assess the validity of events that occurred during labor and delivery along with reported maternal demographics. Sensitivity, specificity, positive and negative predictive values, and kappa scores were calculated.

Results

Postpartum maternal recall and birth certificate data were excellent for infant characteristics (birth weight, gestational age, infant sex) and variables related to labor and delivery (mode of delivery) when compared with medical records. Birth certificate data for labor induction had low sensitivity (46.3%) and positive predictive value (18.3%) compared to medical records. Compared to maternal interview, birth certificate data also had poor agreement for smoking and alcohol use during pregnancy. Agreement between all three methods of data collection was very low for pregnancy weight gain (kappa = 0.07-0.08).

Conclusions

Maternal interview and birth certificate data can be a valid source for collecting data on infant characteristics and events that occurred during labor and delivery. However, caution should be used if solely using birth certificate data to gather data on maternal demographic and/or lifestyle factors.

Birthweight, body size, and growth during childhood and risks of rheumatoid arthritis: a large Danish cohort study

Objectives: Adult obesity may be positively associated with risks of rheumatoid arthritis (RA), but associations with early life body size are unknown. We examined whether birthweight, childhood body mass index (BMI), height, and changes in BMI and height were associated with risks of adult RA.Method: A cohort of 346 602 children (171 127 girls) from the Copenhagen School Health Records Register, born in 1930-1996, with measured weights and heights from 7 to 13 years of age, were included. Information on RA, including serological status, came from national registers from 1977 to 2017. Cox regressions were performed.Results: During a median of 35.1 years of observation time per person, 4991 individuals (3565 women) were registered with RA. Among girls, per BMI z-score, risks of RA and seropositive RA increased by 4-9% and 6-10%, respectively. Girls with overweight had higher risks of RA than girls without overweight. Girls who became overweight by 13 years of age had increased risks of RA compared to girls without overweight at 7 or 13 years (hazard ratio = 1.40, 95% confidence interval 1.19-1.66). For boys, associations between BMI and RA (including seropositive RA) were not statistically significant. Height was not associated with RA (any type) in girls. Taller boys had higher risks of RA, especially seropositive RA. Birthweight was not associated with RA.Conclusions: Among women, childhood adiposity was associated with increased risks of RA. Among men, childhood height was positively associated with risks of RA. These findings support the hypothesis that early life factors may be important in the aetiology of RA.

Birthweight, Childhood Body Mass Index, Height and Growth, and Risk of Polycystic Ovary Syndrome

INTRODUCTION

Adult obesity is linked with polycystic ovary syndrome (PCOS), but the importance of body size at ages before PCOS is diagnosed is unknown.

OBJECTIVE

To investigate associations between a woman's own birthweight, childhood body mass index (BMI), height and growth patterns in relation to her risk of PCOS.

METHODS

We included 65,665 girls from the Copenhagen School Health Records Register, born in the period 1960-1996, with information on birthweight and measured weight and height at the ages of 7-13 years. Overweight was defined using International Obesity Task Force (IOTF) criteria. From the Danish National Patient Register, 606 women aged 15-50 years were identified. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated by Cox regression analysis.

RESULTS

Birthweight was not associated with PCOS. At the age of 7-13 years, girls with overweight had a higher risk of developing PCOS than girls without overweight; HR 2.83 (95% CI 2.34-3.42) at age 7 years and 2.99 (95% CI 2.38-3.76) at age 13 years. Furthermore, girls with overweight at both 7 and 13 years had a higher risk of developing PCOS than girls without overweight or overweight at only one age. Height was positively associated with PCOS risk at all ages. Girls who were persistently tall or changed from tall to average height had a higher risk of developing PCOS than girls with average height growth.

CONCLUSION

Overweight and tall stature in childhood are positively associated with PCOS risk, but birthweight is not.

Risk of gestational diabetes mellitus in nulliparous women - Associations with early life body size and change in body mass index from childhood to adulthood

AIMS

We examined whether a woman's birthweight, childhood height, body mass index (BMI), and BMI changes from childhood to pregnancy were associated with risks of gestational diabetes mellitus (GDM).

METHODS

We studied 13,031 women from the Copenhagen School Health Records Register born 1959-1996 with birthweight and measured anthropometric information at ages 7 and/or 13. The diagnosis of GDM (n = 255) was obtained from a national health register. Risk ratios (RR) were estimated using log-linear binomial regression.

RESULTS

Own birthweight and childhood height were inversely associated with GDM. Girls with overweight at age 7 had a higher risk of GDM than girls with normal-weight (RR: 1.79, 95% CI: 1.31, 2.47). Compared to women with normal-weight in childhood and adulthood, risks of GDM were higher in women who developed overweight from age 7 to pregnancy (RR: 4.62; 3.48, 6.14) or had overweight at both times (RR: 4.71; 3.24, 6.85). In women whose BMI normalized from age 7 to pregnancy the RR for GDM was 1.08 (0.47, 2.46).

CONCLUSIONS

Lower birthweight, shorter childhood height, and higher childhood BMI are associated with increased risks of GDM. Efforts to help girls maintain a normal BMI before pregnancy may be warranted to minimize risks of GDM.

Early life body size and its associations with adult bladder cancer

Background: Adult overweight is a potential bladder cancer (BC) risk factor, but little is known about size earlier in life.Aim: To investigate if birth weight, childhood body mass index (BMI), height and growth are associated with adult BC.Subjects and methods: Anthropometric information from birth and ages 7-13 on 315,763 individuals born 1930-1989 in the Copenhagen School Health Records Register was linked to national registers. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated by Cox regression.Results: 1145 individuals (839 men) were diagnosed with BC. Sex differences were not detected. Childhood BMI had positive associations and height had inverse associations with BC; at age 13, HR = 1.10 (95% CI: 1.02-1.18) per BMI z-score and HR = 0.94 (95% CI: 0.89-1.00) per height z-score. A pattern of above-average increases in BMI from 7 to 13 years had higher hazards of BC than average increases. Above-average growth in height was not significantly associated with BC. Compared with birth weights of 3.5 kg, low (2.5 kg) and high (4.5 kg) values were associated with increased hazards of BC; HR = 1.26 (95% CI: 1.01-1.58) and HR = 1.36 (95% CI: 1.09-1.70), respectively.Conclusions: A high BMI, a short height, excess BMI gain in childhood and low and high birth weights are associated with increased hazards of BC.

Early life body size, growth and risks of systemic lupus erythematosus - A large Danish observational cohort study

OBJECTIVES

Adult obesity may increase the risks of systemic lupus erythematosus (SLE), and there are genetic links between adult height and SLE. Thus, it is plausible that size earlier in life may be important in the aetiology of SLE as well. We investigated whether birthweight, childhood body mass index (BMI; [kg/m²]), height and growth are associated with risks of adult SLE.

METHODS

The study included 346,627 children from the Copenhagen School Health Records Register, born 1930-1996 with measured weights and heights from 7-13 years. Birthweight information was available from 1936. Linkages were made to the Danish National Patient Register for information on registrations of SLE. During follow-up, 435 individuals (366 women) were registered with SLE. Cox proportional hazards regressions were performed to estimate hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

No differences by sex were detected in any of the associations. Birthweight was not associated with SLE risks. Childhood BMI and height were positively and linearly associated with SLE risks. For BMI at age 7, the HR was 1.11 (95% CI: 1.01-1.23) per z-score. For height at age 7, the HR was 1.13 (95% CI: 1.02-1.24) per z-score. The estimates were similar in magnitude across all childhood ages for BMI and height. There were limited indications that change in BMI or growth in height during childhood influence the risks of SLE in adulthood.

CONCLUSIONS

Childhood body size is associated with risks of adult SLE, which supports the hypothesis that early life factors are important in SLE aetiology.

Birth weight, childhood body mass index and height and risks of endometriosis and adenomyosis

Background: Body size in adult life is likely associated with risks of endometriosis and adenomyosis, yet little is known about associations with body size earlier in life.Aim: To examine whether birth weight, childhood body mass index (BMI) and height are associated with risks of endometriosis and adenomyosis.Subjects and methods: From the Copenhagen School Health Records Register, 171,447 girls born 1930-1996, with measured weights and heights at ages 7-13 were included. Outcomes were obtained from health registers. Cox regressions were performed to estimate hazard ratios (HR) and 95% confidence intervals (CI).Results: During follow-up, 2149 endometriosis cases and 1410 adenomyosis cases were diagnosed. Childhood BMI was inversely associated with endometriosis (HR = 0.92 [95% CI: 0.88-0.96] per z-score at age 7). In contrast, childhood height was positively associated with endometriosis (HR = 1.09 [95% CI: 1.05-1.14] per z-score at age 7). Associations with childhood body size did not differ by endometriosis location. Childhood BMI and height had limited associations with adenomyosis. Birth weight was not associated with endometriosis or adenomyosis.Conclusion: Lean and tall girls are more often diagnosed with endometriosis, but not adenomyosis. These findings suggest that indicators of endometriosis risk are already apparent at early ages.

Smallpox and BCG vaccination in childhood and cutaneous malignant melanoma in Danish adults followed from 18 to 49 years

BACKGROUND

Early smallpox and Bacillus Calmette-Guérin (BCG) vaccinations have been associated with reduced risk of cutaneous malignant melanoma (CMM). We assessed the association between pre-school smallpox vaccination and early-school BCG vaccination and CMM in a young Danish population.

METHODS

We conducted a register-based case-cohort study of individuals growing up during the phase-out period of smallpox and BCG vaccination in Denmark (born 1965-1976) utilising the decrease in vaccination during this period. Information on childhood vaccinations and potential confounders from Copenhagen school health records were linked with nationwide registers on cancer (CMM diagnoses), migrations and deaths by personal identification numbers.

RESULTS

The individuals were followed from age 18 until 31/12/2014 (maximum age at end of follow-up, 49 years). 188 cases of CMM occurred in the background population of 46,239 individuals; 172 CMM cases (91%) had full information and were analysed. The adjusted hazard ratio (HR) for CMM by BCG and/or smallpox vaccination compared with neither vaccine was 1.29 (95% confidence interval (CI) 0.72-2.31). For smallpox vaccination only, HR = 1.23 (95% CI 0.53-2.86) for BCG vaccination only, HR = 1.13 (95% CI 0.61-2.09) and for both smallpox and BCG vaccination, HR = 1.75 (95% CI 0.87-3.48) compared with none of these. Vaccination below the age of one year gave similar results.

CONCLUSIONS

We found no strong beneficial effect of smallpox and BCG vaccination against CMM among young adult Danes and with broad confidence intervals our data alone could be compatible with both modest preventive effects, no effects, and modest harmful effects. Our estimates do not contradict a potential modest beneficial effect of neonatal vaccination.

Birthweight and risk of thyroid cancer and its histological types: A large cohort study

BACKGROUND

The aetiology of thyroid cancer is poorly understood, but it is possible that this malignancy has origins early in life. It is, however, currently unknown if birthweight, as an indicator of prenatal growth, is related to thyroid cancer risk.

OBJECTIVE

To investigate if birthweight is associated with the later risk of thyroid cancer and its histological types.

METHODS

246,141 children (120,505 girls, 125,636 boys) from the Copenhagen School Health Records Register, born 1936-1989, were prospectively followed in the Danish Cancer Registry. Cox regressions were used to estimate hazards ratios (HR) and 95% confidence intervals (CI).

RESULTS

During follow up, 241 individuals (172 women, 69 men) were diagnosed with thyroid cancer (162 papillary, 53 follicular). Birthweight was significantly and positively associated with risk of thyroid cancer overall (HR = 1.30 [95% CI: 1.03-1.64] per kilogram). There were no sex differences in the associations. Birthweight was positively and significantly associated with follicular thyroid cancer (HR = 1.74 [95% CI: 1.07-2.82] per kilogram), and although there was an indication of a positive association, it did not reach statistical significance for the more common papillary type (HR = 1.20 [95% CI: 0.90-1.59] per kilogram).

CONCLUSION

A heavier weight at birth is associated with an elevated risk of total and follicular thyroid cancer, which underscores that prenatal exposures may be important in thyroid cancer aetiology.

Genetic and environmental factors affecting birth size variation: a pooled individual-based analysis of secular trends and global geographical differences using 26 twin cohorts

Background

The genetic architecture of birth size may differ geographically and over time. We examined differences in the genetic and environmental contributions to birthweight, length and ponderal index (PI) across geographical-cultural regions (Europe, North America and Australia, and East Asia) and across birth cohorts, and how gestational age modifies these effects.

Methods

Data from 26 twin cohorts in 16 countries including 57 613 monozygotic and dizygotic twin pairs were pooled. Genetic and environmental variations of birth size were estimated using genetic structural equation modelling.

Results

The variance of birthweight and length was predominantly explained by shared environmental factors, whereas the variance of PI was explained both by shared and unique environmental factors. Genetic variance contributing to birth size was small. Adjusting for gestational age decreased the proportions of shared environmental variance and increased the propositions of unique environmental variance. Genetic variance was similar in the geographical-cultural regions, but shared environmental variance was smaller in East Asia than in Europe and North America and Australia. The total variance and shared environmental variance of birth length and PI were greater from the birth cohort 1990-99 onwards compared with the birth cohorts from 1970-79 to 1980-89.

Conclusions

The contribution of genetic factors to birth size is smaller than that of shared environmental factors, which is partly explained by gestational age. Shared environmental variances of birth length and PI were greater in the latest birth cohorts and differed also across geographical-cultural regions. Shared environmental factors are important when explaining differences in the variation of birth size globally and over time.

Genome-wide association study of offspring birth weight in 86 577 women identifies five novel loci and highlights maternal genetic effects that are independent of fetal genetics

Genome-wide association studies of birth weight have focused on fetal genetics, whereas relatively little is known about the role of maternal genetic variation. We aimed to identify maternal genetic variants associated with birth weight that could highlight potentially relevant maternal determinants of fetal growth. We meta-analysed data on up to 8.7 million SNPs in up to 86 577 women of European descent from the Early Growth Genetics (EGG) Consortium and the UK Biobank. We used structural equation modelling (SEM) and analyses of mother–child pairs to quantify the separate maternal and fetal genetic effects. Maternal SNPs at 10 loci (MTNR1B, HMGA2, SH2B3, KCNAB1, L3MBTL3, GCK, EBF1, TCF7L2, ACTL9, CYP3A7) were associated with offspring birth weight at P < 5 × 10⁻⁸. In SEM analyses, at least 7 of the 10 associations were consistent with effects of the maternal genotype acting via the intrauterine environment, rather than via effects of shared alleles with the fetus. Variants, or correlated proxies, at many of the loci had been previously associated with adult traits, including fasting glucose (MTNR1B, GCK and TCF7L2) and sex hormone levels (CYP3A7), and one (EBF1) with gestational duration. The identified associations indicate that genetic effects on maternal glucose, cytochrome P450 activity and gestational duration, and potentially on maternal blood pressure and immune function, are relevant for fetal growth. Further characterization of these associations in mechanistic and causal analyses will enhance understanding of the potentially modifiable maternal determinants of fetal growth, with the goal of reducing the morbidity and mortality associated with low and high birth weights.

Early Life Body Size in Relation to First Intracerebral or Subarachnoid Hemorrhage

Background and Purpose

As risk of hemorrhagic stroke may have early life origins, we investigated associations of birth weight and childhood body mass index (BMI) with adult intracerebral hemorrhage (ICH) or subarachnoid hemorrhage (SAH).

Methods

We included 240,234 Danish schoolchildren, born 1936 to 1989, with information on birth weight and measured weights and heights from 7 to 13 years. We calculated hazard ratios (HRs) and confidence intervals (CIs) for the associations between early life anthropometrics and ICH or SAH, identified through linkage with national registers.

Results

During the study period, 1,947 individuals (39% women) experienced an ICH and 797 individuals (64% women) experienced a SAH. Per 500 g increase in birth weight, women had a 10% decreased risk of SAH (HR, 0.90; 95% CI, 0.83 to 0.97) and men had a 10% decreased risk of ICH (HR, 0.90; 95% CI, 0.85 to 0.95). Birth weight was not associated with risks of ICH in women or SAH in men. In men, a childhood BMI below average (BMI z-score <0) was associated with increased risks of ICH. The association was stronger at older childhood ages, and at 13 years a BMI z-score of –1 was associated with a HR of 1.17 (95% CI, 1.06 to 1.28), and a BMI z-score of –2 with a HR of 1.46 (95% CI, 1.17 to 1.82) for ICH. Childhood BMI was not associated with risks of ICH in women or with risks of SAH in both sexes.

Conclusions

Early life body size is associated with ICH and SAH, and the associations differ by sex.

Association between birth weight and educational attainment: an individual-based pooled analysis of nine twin cohorts

BACKGROUND

There is evidence that birth weight is positively associated with education, but it remains unclear whether this association is explained by familial environmental factors, genetic factors or the intrauterine environment. We analysed the association between birth weight and educational years within twin pairs, which controls for genetic factors and the environment shared between co-twins.

METHODS

The data were derived from nine twin cohorts in eight countries including 6116 complete twin pairs. The association between birth weight and educational attainment was analysed both between individuals and within pairs using linear regression analyses.

RESULTS

In between-individual analyses, birth weight was not associated with educational years. Within-pairs analyses revealed positive but modest associations for some sex, zygosity and birth year groups. The greatest association was found in dizygotic (DZ) men (0.65 educational years/kg birth weight, p=0.006); smaller effects of 0.3 educational years/kg birth weight were found within monozygotic (MZ) twins of both sexes and opposite-sex DZ twins. The magnitude of the associations differed by birth year in MZ women and opposite-sex DZ twins, showing a positive association in the 1915-1959 birth cohort but no association in the 1960-1984 birth cohort.

CONCLUSION

Although associations are weak and somewhat inconsistent, our results suggest that intrauterine environment may play a role when explaining the association between birth weight and educational attainment.

Birth size and gestational age in opposite-sex twins as compared to same-sex twins: An individual-based pooled analysis of 21 cohorts

It is well established that boys are born heavier and longer than girls, but it remains unclear whether birth size in twins is affected by the sex of their co-twin. We conducted an individual-based pooled analysis of 21 twin cohorts in 15 countries derived from the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), including 67,850 dizygotic twin individuals. Linear regression analyses showed that boys having a co-twin sister were, on average, 31 g (95% CI 18 to 45) heavier and 0.16 cm (95% CI 0.045 to 0.274) longer than those with a co-twin brother. In girls, birth size was not associated (5 g birth weight; 95% CI −8 to −18 and −0.089 cm birth length; 95% CI −0.202 to 0.025) with the sex of the co-twin. Gestational age was slightly shorter in boy-boy pairs than in boy-girl and girl-girl pairs. When birth size was standardized by gestational age, the magnitude of the associations was attenuated in boys, particularly for birth weight. In conclusion, boys with a co-twin sister are heavier and longer at birth than those with a co-twin brother. However, these differences are modest and partly explained by a longer gestation in the presence of a co-twin sister.

Birth weight and the risk of histological subtypes of ovarian and endometrial cancers: Results from the Copenhagen School Health Records Register

BACKGROUND

Studies of birth weight associations with ovarian and endometrial cancer risks are limited with inconsistent results, and none has evaluated associations by histologic subtype. We utilized prospectively collected birth weight information to investigate the association with risk of ovarian and endometrial cancers overall and by histologic subtype.

METHODS

162,559 girls, born from 1930 to 1989, from the Copenhagen School Health Records Register (CSHRR) were followed prospectively via linkage with the Danish health registers. Ovarian (n=666) and endometrial (n=694) cancers were identified from 1978 to 2014. Cox regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Women with lower (2.0-3.25 vs. 3.26-3.75kg) and higher (3.75-5.5 vs. 3.26-3.75kg) birth weights had increased risks of ovarian cancer overall [HR (95% CI): 1.27 (1.06-1.52); 1.51 (1.21-1.87), respectively] and serous ovarian cancers [1.54 (1.19-1.98); 1.98 (1.47-2.67), respectively]. A decreased risk of Type II endometrial tumors was suggested per kilogram increase in birth weight [HR (95% CI): 0.63 (0.40-1.00)].

CONCLUSIONS

Our results suggest that both lower and higher birth weights were associated with increased ovarian cancer risk and associations were particularly strong for serous ovarian cancer, the most common subtype. Birth weight was not associated with most types of endometrial cancer.

Associations between birth weight and colon and rectal cancer risk in adulthood

BACKGROUND

Birth weight has inconsistent associations with colorectal cancer, possibly due to different anatomic features of the colon versus the rectum. The aim of this study was to investigate the association between birth weight and colon and rectal cancers separately.

METHODS

193,306 children, born from 1936 to 1972, from the Copenhagen School Health Record Register were followed prospectively in Danish health registers. Colon and rectal cancer cases were defined using the International Classification of Disease version 10 (colon: C18.0-18.9, rectal: 19.9 and 20.9). Only cancers classified as adenocarcinomas were included in the analyses. Cox regressions were used to estimate hazard ratios (HR) and 95% confidence intervals (CI). Analyses were stratified by birth cohort and sex.

RESULTS

During 3.8 million person-years of follow-up, 1465 colon and 961 rectal adenocarcinomas were identified. No significant sex differences were observed; therefore combined results are presented. Birth weight was positively associated with colon cancers with a HR of 1.14 (95% CI, 1.04-1.26) per kilogram of birth weight. For rectal cancer a significant association was not observed for birth weights below 3.5kg. Above 3.5kg an inverse association was observed (at 4.5kg, HR=0.77 [95% CI, 0.61-0.96]). Further, the associations between birth weight and colon and rectal cancer differed significantly from each other (p=0.006).

CONCLUSIONS

Birth weight is positively associated with the risk of adult colon cancer, whereas the results for rectal cancer were inverse only above values of 3.5kg. The results underline the importance of investigating colon and rectal cancer as two different entities.

Pregnancy loss history at first parity and selected adverse pregnancy outcomes

PURPOSE

To evaluate the association between pregnancy loss history and adverse pregnancy outcomes.

METHODS

Pregnancy history was captured during a computer-assisted personal interview for 21,277 women surveyed in the National Survey of Family Growth (1995-2013). History of pregnancy loss (<20 weeks) at first parity was categorized in three ways: number of losses, maximum gestational age of loss(es), and recency of last pregnancy loss. We estimated risk ratios for a composite measure of selected adverse pregnancy outcomes (preterm, stillbirth, or low birthweight) at first parity and in any future pregnancy, separately, using predicted margins from adjusted logistic regression models.

RESULTS

At first parity, compared with having no loss, having 3+ previous pregnancy losses (adjusted risk ratio (aRR) = 1.66 [95% CI = 1.13, 2.43]), a maximum gestational age of loss(es) at ≥10 weeks (aRR = 1.28 [1.04, 1.56]) or having experienced a loss 24+ months ago (aRR = 1.36 [1.10, 1.68]) were associated with increased risks of adverse pregnancy outcomes. For future pregnancies, only having a history of 3+ previous pregnancy losses at first parity was associated with increased risks (aRR = 1.97 [1.08, 3.60]).

CONCLUSION

Number, gestational age, and recency of pregnancy loss at first parity were associated with adverse pregnancy outcomes in U.S. women.