Reproduction after the loss of a child: a population-based matched cohort study.

STUDY QUESTION: Is the death of a child associated with higher subsequent fertility? SUMMARY ANSWER: Women who had lost a child had higher fertility both shortly after the loss and throughout the entire follow-up, independent of the child's age at the time of death. WHAT IS KNOWN ALREADY: Women who lose a child in the perinatal period often have another child shortly after. However, to our knowledge no previous study has investigated if the death of an older child affects reproductive behavior. STUDY DESIGN, SIZE, DURATION: The source population for this matched cohort study consisted of all women who gave birth in Denmark from 1978 to 2004 and in Sweden from 1973 to 2002 (N = 1 979 958). Women were followed through to the end of 2008 in Denmark and the end of 2006 in Sweden. PARTICIPANTS/MATERIALS, SETTING, METHODS: Women who had lost a child before the age of 45 years during the study period (exposed group; n = 36 511) were matched with up to five women who were from the same country and of similar age and family characteristics and had not lost a child at the time of matching (unexposed group; n = 182 522). MAIN RESULTS AND THE ROLE OF CHANCE: During follow-up, 74% of exposed and 46% of unexposed women had another birth (live- or stillbirth) after a gestation of 28 weeks or more. Compared with unexposed women, exposed women had a shorter interpregnancy interval and, consequently, a higher rate of conception leading to a birth (HR = 5.5 [95% CI: 5.4-5.6]). Rates for exposed women were higher from the first month following the child's death, but the largest difference was between 2 and 3 months after the event. This pattern was independent of the age of the deceased child. Exposed women had more subsequent children than unexposed, leading to a comparable number of living children at the end of follow-up. LIMITATIONS, REASONS FOR CAUTION: The use of population-based registers allows for the inclusion of virtually all eligible women and nearly complete follow-up; the potential for selection bias is thus negligible. However, only pregnancies that led to a live birth or a stillbirth could be identified, thus fetal losses occurring before week 28 of gestation were missing. WIDER IMPLICATIONS OF THE FINDINGS: Our findings corroborate the previous evidence suggesting that women try to conceive again shortly after a perinatal death, and many succeed. In addition, this is the first study to investigate the reproductive trajectory after losing an older child. The current study indicates that most women who lose a child between the ages of 6 months and 5 years conceive shortly after the loss, and they have a comparable number of living children at the end of the follow-up compared to those who do not lose a child. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by Grant ERC-2010-StG-260242 from the European Research Council, 176673 and 186200 from the Nordic Cancer Union, DFF-6110-00019 from the Danish Council for Independent Research, 904414 and 15199 from TrygFonden, Karen Elise Jensens Fond (2016), and the Program for Clinical Research Infrastructure (PROCRIN) established by the Lundbeck Foundation and the Novo Nordisk Foundation. The authors do not declare any conflicts of interests. TRIAL REGISTRATION NUMBER: N/A.

A policy of routine umbilical cord blood gas analysis decreased missing samples from high-risk births.

AIM: This study compared obstetric units practicing routine or selective umbilical cord blood gas analysis, with respect to the risk of missing samples in high-risk deliveries and in infants with birth asphyxia. METHODS: This was a Swedish population-based cohort study that used register data for 155 235 deliveries of live singleton infants between 2008 and 2014. Risk ratios and 95% confidence intervals were calculated to estimate the association between routine and selective umbilical cord blood gas sampling strategies and the risk of missing samples. RESULTS: Selective sampling increased the risk ratios when routine sampling was used as the reference, with a value of 1.0, and these were significant in high-risk deliveries and birth asphyxia. The risk ratios for selective sampling were large-for-gestational age (9.07), preterm delivery at up to 36 weeks of gestation (8.24), small-for-gestational age (7.94), two or more foetal scalp blood samples (5.96), an Apgar score of less than seven at one minute (2.36), emergency Caesarean section (1.67) and instrumental vaginal delivery (1.24). CONCLUSION: Compared with routine sampling, selective umbilical cord blood gas sampling significantly increased the risks of missing samples in high-risk deliveries and in infants with birth asphyxia.

Advanced maternal age increases the risk of very preterm birth, irrespective of parity: a population-based register study.

OBJECTIVE: To investigate whether advanced maternal age is associated with preterm birth, irrespective of parity. DESIGN: Population-based registry study. SETTING: Swedish Medical Birth Register. POPULATION: First, second, and third live singleton births to women aged 20 years or older in Sweden, from 1990 to 2011 (n = 2 009 068). METHODS: Logistic regression analysis was used in each parity group to estimate risks of very and moderately preterm births to women at 20-24, 25-29, 30-34, 35-39, and 40 years or older, using 25-29 years as the reference group. Odds ratios (ORs) were adjusted for year of birth, education, country of birth, smoking, body mass index, and history of preterm birth. Age-related risks of spontaneous and medically indicated preterm births were also investigated. MAIN OUTCOME MEASURES: Very preterm (22-31 weeks of gestation) and moderately preterm (32-36 weeks) births. RESULTS: Risks of very preterm birth increased with maternal age, irrespective of parity: adjusted ORs in first, second, and third births ranged from 1.18 to 1.28 at 30-34 years, from 1.59 to 1.70 at 35-39 years, and from 1.97 to 2.40 at ≥40 years. In moderately preterm births, age-related associations were weaker, but were statistically significant from 35-39 years in all parity groups. Advanced maternal age increased the risks of both spontaneous and medically indicated preterm births. CONCLUSIONS: Advanced maternal age is associated with an increased risk of preterm birth, irrespective of parity, especially very preterm birth. Women aged 35 years and older, expecting their first, second, or third births, should be regarded as a risk group for very preterm birth. TWEETABLE ABSTRACT: Women aged 35 years and older should be regarded as a risk group for very preterm birth, irrespective of parity.

Maternal tobacco use and extremely premature birth - a population-based cohort study.

OBJECTIVE: To study the associations of maternal tobacco use (smoking or use of snuff) and risk of extremely preterm birth, and if tobacco cessation before antenatal booking influences this risk. To study the association between tobacco use and spontaneous or medically indicated onset of delivery. DESIGN: Population-based cohort study. SETTING: Sweden. POPULATION: All live singleton births, registered in the Swedish Medical Birth Register, 1999-2012. METHODS: Odds ratios (OR) with 95% confidence intervals (CI) were calculated using multiple logistic regression analysis. MAIN OUTCOME MEASURES: Extremely preterm birth (<28 weeks of gestation), very preterm birth (28-31 weeks), moderately preterm birth (32-36 weeks). RESULTS: Maternal snuff use (OR 1.58; 95% CI: 1.14-2.21) and smoking (OR 1.61; 95% CI: 1.39-1.87 and OR 1.91; 95% CI: 1.53-2.39 for moderate and heavy smoking, respectively) were associated with an increased risk of extremely preterm birth. When cessation of tobacco use was obtained there was no increased risk of preterm birth. Snuff use was associated with a twofold risk increase of medically indicated extremely preterm birth, whereas smoking was associated with increased risks of both medically indicated and spontaneous extremely preterm birth. CONCLUSIONS: Snuff use and smoking in pregnancy were associated with increased risks of extremely preterm birth. Women who stopped using tobacco before the antenatal booking had no increased risk. These findings indicate that nicotine, the common substance in cigarettes and snuff, is involved in the mechanisms behind preterm birth. The use of nicotine should be minimized in pregnancy. TWEETABLE ABSTRACT: Tobacco use increases risk of extremely preterm birth. Cessation is preventive. Avoid nicotine in pregnancy.

Pregnancy hypertensive disease and risk of dementia and cardiovascular disease in women aged 65 years or older: a cohort study.

OBJECTIVE: The primary aim was to study pregnancy hypertensive disease and subsequent risk of dementia. The second aim was to study if the increased risks of cardiovascular disease (CVD) and stroke after pregnancy hypertensive disease persist in an elderly population. DESIGN: Cohort study. SETTING: Sweden. POPULATION OR SAMPLE: 3232 women 65 years or older (mean 71 years) at inclusion. METHODS: Cox proportional hazards regression analyses were used to calculate risks of dementia, CVD and/or stroke for women exposed to pregnancy hypertensive disease. Exposure data were collected from an interview at inclusion during the years 1998-2002. Outcome data were collected from the National Patient Register and Cause of Death Register from the year of inclusion until the end of 2010. Age at inclusion was set as a time-dependent variable, and adjustments were made for body mass index, education and smoking. MAIN OUTCOME MEASURES: Dementia, CVD, stroke. RESULTS: During the years of follow-up, 7.6% of the women exposed to pregnancy hypertensive disease received a diagnosis of dementia, compared with 7.4% among unexposed women (HR 1.19; 95% CI 0.79 to 1.73). The corresponding rates for CVD were 22.9% for exposed women and 19.0% for unexposed women (HR 1.29; 95% CI 1.02 to 1.61), and for stroke 13.4% for exposed women and 10.7% for unexposed women (HR 1.36; 95% CI 1.00 to 1.81). CONCLUSIONS: There was no increased risk of dementia after self-reported pregnancy hypertensive disease in our cohort. We found that the previously reported increased risk of CVD and stroke after pregnancy hypertensive disease persists in an older population.

Prolonged second stage of labour, maternal infectious disease, urinary retention and other complications in the early postpartum period.

OBJECTIVE: To study the association between duration of second stage of labour and risks of maternal complications (infection, urinary retention, haematoma or ruptured sutures) in the early postpartum period. DESIGN: Population-based cohort study. SETTING AND SAMPLE: We included 72 593 mothers with singleton vaginal deliveries at ≥37 weeks of gestation in cephalic presentation, using the obstetric database from the Stockholm-Gotland region in Sweden, 2008-12. METHODS: Logistic regression analysis. Odds ratios (ORs) with 95% confidence intervals (95% CI) were calculated and adjustments were made for maternal age, body mass index, height, smoking, cohabitation, gestational age, labour induction, epidural analgesia and oxytocin augmentation. RESULTS: Rates of any complication varied by parity from 7.3% in parous women with previous caesarean section, 4.8% in primiparas and 1.7% in parous women with no previous caesarean section. Compared with a second stage <1 hour, the adjusted ORs for any complication (95% CI) in primiparas were for 1 to <2 hours 1.28 (1.11-1.47); 2 to <3 hours 1.54 (1.32-1.79), 3 to <4 hours 1.63 (1.38-1.93) and ≥4 hours 2.08 (1.74-2.49). The corresponding adjusted ORs for parous women without previous caesarean were 2.27 (1.78-2.90), 2.97 (2.09-4.22), 3.65 (2.25-5.94) and 3.16 (1.44-6.94), respectively. The adjusted ORs for women with previous caesarean were for 1 to <2 hours 1.62 (1.13-2.32); 2 to <3 hours 1.56 (1.00-2.43), 3 to <4 hours 2.42 (1.52-3.87), and ≥4 hours 2.31 (1.25-4.24). CONCLUSIONS: Risks of maternal complications in the postpartum period increase with duration of second stage of labour also after accounting for maternal, pregnancy and delivery characteristics. Special attention has to be given to parous women with previous caesarean deliveries.

Delivery by caesarean section and childhood cancer: a nationwide follow-up study in three countries.

OBJECTIVE: To investigate the association between delivery by caesarean section and risk of childhood cancer. DESIGN: A population-based, follow-up study using register data from three countries. SETTING: Denmark, Sweden and Finland. POPULATION: Children born in Denmark (1973-2007), Sweden (1973-2006) and Finland (randomly selected sample of 90%, 1987-2007; n = 7,029,843). METHODS: Exposure was delivery by caesarean section and the outcome was childhood cancer diagnosis. Follow-up started from birth and ended at the first of the following dates: cancer diagnosis, death, emigration, day before 15th birthday or end of follow-up. Cox regression was used to obtain hazard ratios. MAIN OUTCOME MEASURES: Childhood cancer diagnosis. RESULTS: A total of 882,907 (12.6%) children were delivered by caesarean section. Of these, 30.3% were elective (n = 267,603), 35.9% unplanned (n = 316,536) and 33.8% had no information on planning (n = 298,768). Altogether, 11,181 children received a cancer diagnosis. No evidence of an increased risk of childhood cancer was found for children born by caesarean section (hazard ratio, 1.05; 95% confidence interval, 0.99, 1.11). No association was found for any major type of childhood cancer, or when split by the type of caesarean section (elective/unplanned). CONCLUSION: The evidence does not suggest that caesarean section is a risk factor for the overall risk of childhood cancer and possibly not for subtypes of childhood cancer either.

Hyperemesis gravidarum and risks of placental dysfunction disorders: a population-based cohort study.

OBJECTIVE: To study whether pregnancies complicated by hyperemesis gravidarum in the first (<12 weeks) or second (12-21 weeks) trimester are associated with placental dysfunction disorders. DESIGN: Population-based cohort study. SETTING: Sweden. POPULATION: All pregnancies in the Swedish Medical Birth Register estimated to have started on 1 January 1997 or later and ended in a single birth on 31 December 2009 or earlier (n = 1 156 050). METHODS: Odds ratios with 95% confidence intervals were estimated for placental dysfunction disorders in women with an inpatient diagnosis of hyperemesis gravidarum, using women without inpatient diagnosis of hyperemesis gravidarum as reference. Risks were adjusted for maternal age, parity, body mass index, height, smoking, cohabitation with the infant's father, infant's sex, mother's country of birth, education, presence of hyperthyreosis, pregestational diabetes mellitus, chronic hypertension and year of infant birth. MAIN OUTCOME MEASURES: Placental dysfunction disorders, i.e. pre-eclampsia, placental abruption, stillbirth and small for gestational age (SGA). RESULTS: Women with hyperemesis gravidarum in the first trimester had only a slightly increased risk of pre-eclampsia. Women with hyperemesis gravidarum with first admission in the second trimester had a more than doubled risk of preterm (<37 weeks) pre-eclampsia, a threefold increased risk of placental abruption and a 39% increased risk of an SGA birth (adjusted odds ratios [95% confidence intervals] were: 2.09 [1.38-3.16], 3.07 [1.88-5.00] and 1.39 [1.06-1.83], respectively). CONCLUSIONS: There is an association between hyperemesis gravidarum and placental dysfunction disorders, which is especially strong for women with hyperemesis gravidarum in the second trimester.

Changes in snuff and smoking habits in Swedish pregnant women and risk for small for gestational age births.

OBJECTIVE: To examine associations between antenatal exposure to Swedish oral moist snuff (which includes essentially only nicotine) and to smoking and risks of small-for-gestational-age (SGA) births and to compare risks among women who stopped or continued using snuff or smoking during pregnancy. DESIGN: Population-based cohort study. SETTING: Sweden. POPULATION: All live singleton births in Sweden 1999-2010. METHODS: Odds ratios (OR) with 95% confidence intervals (CI) were calculated using multiple logistic regression analysis. MAIN OUTCOME MEASURES: SGA birth, also stratified into preterm (≤36 weeks of gestation) and term (≥37 weeks of gestation) SGA births. RESULTS: Compared with non-tobacco users in early pregnancy, snuff users and above all smokers in early pregnancy had increased risks of SGA births: adjusted ORs (95% CI) were 1.26 (1.09-1.46) and 2.55 (2.43-2.67), respectively). Snuff use had, if anything, a stronger association with preterm SGA than term SGA, whereas the opposite was true for smoking. Compared with non-tobacco users, women who stopped using snuff before their first visit to antenatal care had no increased risks of preterm or term SGA, and women who stopped using snuff later during pregnancy had no increased risk of term SGA. Smoking cessation early in pregnancy was associated with a larger reduction in risk than smoking cessation later in pregnancy. CONCLUSIONS: As both smoking and snuff use influence risk of SGA, both nicotine but above all tobacco combustion products are involved in the mechanisms by which maternal smoking increases the risk of SGA.

Effect of Swedish snuff (snus) on preterm birth.

OBJECTIVE: To compare the effects of Swedish snuff and cigarette smoking on risks of preterm birth. DESIGN: Population-based cohort study. SETTING: Sweden. POPULATION: All live, singleton births in Sweden 1999-2006. METHODS: Odds ratios (OR) with 95% confidence intervals (CI) were used to estimate relative risks for preterm birth in snuff users (n = 7607), light smokers (1-9 cigarettes/day; n = 41 436) and heavy smokers (ten or more cigarettes/day; n = 16 951) using non-tobacco users (n = 503 957) as reference. MAIN OUTCOME MEASURES: Very (<32 weeks) and moderately (32-36 weeks) preterm birth. RESULTS: Compared with non-tobacco users, snuff users had increased risks of both very (adjusted OR 1.38; 95% CI 1.04-1.83) and moderately (adjusted OR 1.25; 95% CI 1.12-1.40) preterm birth. Compared with non-tobacco users, light smokers had increased risks of both very (adjusted OR 1.60; 95% CI 1.42-1.81) and moderately (adjusted OR: 1.18; 95% CI: 1.12-1.24) preterm birth, and heavy smokers had even higher risks. Among smokers, but not among snuff users, the risk was more pronounced for spontaneous than induced preterm birth. CONCLUSIONS: The use of Swedish snuff was associated with increased risks of very and moderately preterm birth with both spontaneous and induced onsets. Swedish snuff is not a safe alternative to cigarette smoking during pregnancy.

Influence of hysterectomy on fistula formation in women with diverticulitis.

BACKGROUND: : Diverticulitis is a risk factor for fistula formation but little is known about the influence of hysterectomy in this association. A population-based nationwide matched cohort study was performed to determine the risk of fistula formation in hysterectomized women with, and without, diverticulitis. METHODS: : Women who had a hysterectomy between 1973 and 2003, and a matched control cohort, were identified from the Swedish Inpatient Register. Incidence of diverticulitis and fistula surgery was determined by cross-linkage to the Register, and risk was estimated using a Cox regression model. RESULTS: : In a cohort of 168 563 hysterectomized and 614 682 non-hysterectomized women (mean follow-up 11.0 and 11.5 years respectively), there were 14 051 cases of diverticulitis and 851 fistulas. Compared with women who had neither hysterectomy nor diverticulitis, the risk of fistula surgery increased fourfold in hysterectomized women without diverticulitis (hazard ratio (HR) 4.0 (95 per cent confidence interval (c.i.) 3.5 to 4.7)), sevenfold in non-hysterectomized women with diverticulitis (HR 7.6 (4.8 to 12.1)) and 25-fold in hysterectomized women with diverticulitis (HR 25.2 (15.5 to 41.2)). CONCLUSION: : Diverticulitis, and to a lesser extent hysterectomy, is strongly associated with the risk of fistula formation. Hysterectomized women with diverticulitis have the highest risk of developing surgically managed fistula.

Birth characteristics and risk of colorectal cancer: a study among Swedish twins.

Type-2 diabetes increases the risk of colorectal cancer, and is also associated with low birth weight. However, we found no evidence of associations between birth characteristics and risk of colorectal cancer (m=248) among Swedish twins.

Trends in socioeconomic differences in Finnish perinatal health 1991-2006.

BACKGROUND: Socioeconomic differences in perinatal health decreased in Finland in the late 1990s. Whether the decreasing socioeconomic differences in perinatal health observed in Finland in the late 1990s have continued in 2000-6 was studied. METHODS: The data were based on 965 443 births and 931 285 singletons recorded between 1991 and 2006 in the Finnish Medical Birth Register. Information on socioeconomic position was based on maternal occupation. Perinatal health was measured with six different indicators. RESULTS: The proportions of preterm, low birthweight and SGA (small-for-gestational-age) births remained stable during the study period, but decreased for LGA (large-for-gestational-age) births and perinatal death. After adjustment for maternal background variables, the socioeconomic differences in preterm and low-birthweight births decreased in the late 1990s and remained low thereafter. In 2003-6, blue-collar workers had a 14% (95% CI 7% to 22%) higher risk for preterm birth and a 25% (95% CI 16% to 34%) higher risk for low birthweight than upper white-collar workers. For SGA, the socioeconomic differences remained unchanged, and the excess risk for blue-collar workers was 44% (95% CI 31% to 58%) in 2003-6. For LGA, the socioeconomic differences increased, and the highest excess risks were obtained among lower white-collar (23%, 95% CI 15% to 33%) and blue-collar workers (24%, 95% CI 14% to 36%). The differences in perinatal mortality decreased until the late 1990s, but increased thereafter. In 2003-6, lower white-collar and blue-collar workers had the highest excess risks: 46% (95% CI 20% to 77%) and 44% (95% CI 13% to 83%), respectively. CONCLUSIONS: The trends in social inequality in perinatal health outcomes were diverging by indicator. The positive trend on diminishing socioeconomic differences found in the 1990s seems to have come to an end.

Prenatal ultrasound and the risk of childhood brain tumour and its subtypes.

We carried out a nationwide case-control study of childhood brain tumours in Sweden (n=512) by histological subtype in relation to prenatal ultrasound, extracting data from antenatal records and the Medical Birth Register. We found no increased risk for brain tumour after ultrasound exposure, either for all tumours or for any subgroup.

Scholastic achievement at age 16 and risk of schizophrenia and other psychoses: a national cohort study.

BACKGROUND: There is abundant evidence that schizophrenia is associated with cognitive deficits in childhood. However, previous studies investigating school performance have been inconclusive. Furthermore, there are several biological and social factors that could confound the association. We investigated whether school performance at age 16 is associated with risk of adult schizophrenia and other psychoses in a large national cohort, while controlling for multiple confounders. METHOD: Using a national sample of 907 011 individuals born in Sweden between 1973 and 1983, we used Cox regression to assess whether scholastic achievement at age 15-16 predicted hospital admission for psychosis between ages 17 and 31, adjusting for potential confounders. RESULTS: Poor school performance was associated with increased rates of schizophrenia [hazard ratio (HR) 3.9, 95% confidence interval (CI) 2.8-5.3], schizo-affective disorder (HR 4.2, 95% CI 1.9-9.1) and other psychoses (HR 3.0, 95% CI 2.3-4.0). Receiving the lowest (E) grade was significantly associated with risk for schizophrenia and other psychoses in every school subject. There was no evidence of confounding by migrant status, low birthweight, hypoxia, parental education level or socio-economic group. CONCLUSIONS: Poor school performance across all domains is strongly associated with risk for schizophrenia and other psychoses.

Prenatal X-ray exposure and childhood brain tumours: a population-based case-control study on tumour subtypes.

We investigated childhood brain tumours by histological subtype in relation to prenatal X-ray among all children, less than 15 years of age, born in Sweden between 1975 and 1984. For each case, one control was randomly selected from the Medical Birth Register, and exposure data on prenatal X-ray were extracted blindly from antenatal medical records. Additional information on maternal reproductive history was obtained from the Medical Birth Register. We found no overall increased risk for childhood brain tumour after prenatal abdominal X-ray exposure (adjusted odds ratio (OR): 1.02, 95% confidence interval (CI): 0.64-1.62); primitive neuroectodermal tumours had the highest risk estimate (OR: 1.88, 95% CI: 0.92-3.83).

The influence of maternal smoking habits on the risk of subsequent stillbirth: is there a causal relation?

OBJECTIVE: Maternal smoking has previously been associated with risk of stillbirth. If women who quit smoking reduce their risk of stillbirth, the hypothesis of a causal association would be supported. DESIGN: Prospective cohort study. SETTING: Nationwide study in Sweden. POPULATION: All primiparous women who delivered their first and second consecutive single births between 1983 and 2001, giving a total number of 526,691 women. METHOD: A population-based Swedish study with data from the Medical Birth Registry, the Immigration Registry and the Education Registry. Logistic regression analyses were used to estimate odds ratios, using 95% confidence intervals. MAIN OUTCOME MEASURE: Stillbirth in the second pregnancy. RESULTS: Compared with nonsmokers in both pregnancies, women who smoked during the first pregnancy but not during the second do not have an increased risk of stillbirth (OR 1.02; 95% CI 0.79-1.30), while corresponding risk among women who smoked during both pregnancies was 1.35 (95% CI 1.15-1.58). CONCLUSION: The result supports that maternal smoking during pregnancy is causally associated with stillbirth risk. Smoking is a preventable cause of stillbirth, and smoking interventions is an important issue in antenatal care.

Cigarette smoking and the risk of goitre and thyroid nodules amongst parous women.

OBJECTIVES: To clarify the mechanisms by which smoking is associated to toxic and nontoxic goitre and thyroid nodules. DESIGN: Cohort study. SETTING: Sweden. SUBJECTS: A cohort of 874,507 parous women identified through the Medical Birth Registry, with smoking behaviour assessed through self-reported information at the first pre-natal visit, and follow-up between 1983 and 1997. MAIN OUTCOME MEASURES: Hospital diagnoses of toxic and nontoxic goitre and thyroid nodules, identified by record-linkage with the national Inpatient Registry. Cox regression was employed to estimate the hazard ratio (HR) of smokers compared with nonsmokers and the corresponding 95% confidence limits (CL). RESULTS: There was a significantly increased risk of goitre and nodules amongst smokers. The positive association was stronger for toxic (age adjusted HR = 1.94, CL = 1.74-2.16) than for nontoxic goitre and nodules (age-adjusted HR = 1.26; CL = 1.14-1.38). There was generally no clear risk trend with regard to amount smoked (below and above 10 cigarettes per day). Elevated body mass attenuated these associations, whilst being born in Swedish areas of endemic goitre enhanced the association with nontoxic goitre and nodules. CONCLUSIONS: Smoking enhances the risk of thyroid goitre and nodules requiring hospital admission. Iodine deficiency and body weight are likely to be important modifiers of the risk of thyroid hyperplastic diseases amongst smokers.

Low birthweight and Type 2 diabetes: a study on 11 162 Swedish twins.

BACKGROUND: To investigate the association between low birthweight and diabetes in a population-based Swedish twin sample. Method A cohort of 11 162 same-sexed Swedish twins born between 1906 and 1958 was used in order to investigate the risk of developing Type 2 diabetes between and within twin pairs by utilizing random effects linear models. RESULTS: Between pairs there was a significant increase in risk of developing Type 2 diabetes for a 1-kg increase in their mean birthweight (odds ratio [OR] = 2.13; P < 0.01), adjusted for age, sex, body mass index (BMI), and smoking status. The corresponding risk within pair was 2.03 (P = 0.07) for monozygotic twins and 1.15 (P = 0.71) for dizygotic twins. The test of the heterogeneity of the within and between effects showed no significant difference between the estimates. CONCLUSIONS: The study suggests that reduced fetal growth increase the risk of Type 2 diabetes due to an in utero programming effect possibly caused by intrauterine malnutrition. However, it does not exclude the possibility of a common genetic mechanism.

Catch-up growth in females born short for gestational age reduces the risk of giving birth to short-for-gestational-age infants.

OBJECTIVES: The aim of the present study was to study the effect of catch-up growth on the offspring's length at birth among females born short for gestational age. METHODS: Data of 1,363 females born short for gestational age (<-2 standard deviation scores) were obtained from the Swedish Birth Register. The females were included in the register both as babies and mothers. The effect of catch-up growth on the offspring's birth length was studied. RESULTS: Short adult stature was associated with a threefold increase in the risk of giving birth to a short infant [OR 3.08 (CI 1.73-5.50)] and smoking increased the risk in a dose-dependent manner. Overweight was associated with a reduced risk [OR 0.46 (CI 0.22-0.96)] of giving birth to a short infant. CONCLUSION: Catch-up growth to normal adult stature among women born short for gestational age is associated with a reduced risk of giving birth to a short-for-gestational-age infant.