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Lars J Vatten

Publications and source records attributed to Lars J Vatten.

At least 19 recordsLinked to original sources
PubMed2007

Association between blood pressure and serum thyroid-stimulating hormone concentration within the reference range: a population-based study.

CONTEXT: The association between thyroid function and blood pressure is insufficiently studied. OBJECTIVE: The objective of the investigation was to study the association between TSH within the reference range and blood pressure. DESIGN AND SETTING: This was a cross-sectional, population-based study. SUBJECTS: A total of 30,728 individuals without previously known thyroid disease were studied. MAIN OUTCOME MEASURES: The main outcome measures were mean systolic and diastolic blood pressure and pulse pressure and odds ratio for hypertension (>140/90 mm Hg or current or previous use of antihypertensive medication), according to categories of TSH. RESULTS: Within the reference range of TSH (0.50-3.5 mU/liter), there was a linear increase in blood pressure with increasing TSH. The average increase in systolic blood pressure was 2.0 mm Hg [95% confidence interval (CI) 1.4-2.6 mm Hg] per milliunit per liter increase in TSH among men, and 1.8 mm Hg (95% CI 1.4-2.3 mm Hg) in women. The corresponding increase in diastolic blood pressure was 1.6 mm Hg (95% CI 1.2-2.0 mm Hg) in men and 1.1 mm Hg (95% CI 0.8-1.3 mm Hg) in women. Comparing TSH of 3.0-3.5 mU/liter (upper part of the reference) with TSH of 0.50-0.99 mU/liter (lower part of the reference), the odds ratio for hypertension was 1.98 (95% CI 1.56-2.53) in men and 1.23 (95% CI 1.04-1.46) in women. CONCLUSION: Within the reference range of TSH, we found a linear positive association between TSH and systolic and diastolic blood pressure that may have long-term implications for cardiovascular health.

Adult↗
PubMed2006

Recreational physical activity and risk of prostate cancer: A prospective population-based study in Norway (the HUNT study).

Physical activity has been studied in relation to prostate cancer risk, but the findings have been inconclusive. We prospectively examined the association between self-reported recreational physical activity and overall risk of prostate cancer, risk of advanced disease and risk of prostate cancer death in a cohort of 29,110 Norwegian men. Incident prostate cancers were obtained from the Norwegian Cancer Registry, and prostate cancer deaths were obtained from the national Cause of Death Registry. During 17 years of follow-up, 957 incident cases were identified, 266 of them were advanced (i.e. metastases at diagnosis) and 354 of the incident cases died from prostate cancer. In multivariable analysis, frequency and duration of exercise were inversely associated with the risk of advanced prostate cancer (p for trend = 0.04 and 0.02). We computed a summary score that combined frequency, duration and intensity of exercise, and this score showed inverse associations with advanced prostate cancer risk and mortality (p for trend = 0.02 and 0.07). Compared to men who reported no activity, the relative risks (95% confidence intervals) among men in the highest category of physical exercise was 0.64 (0.43-0.95) for advanced prostate cancer and 0.67 (0.48-0.94) for prostate cancer death. We found no association between physical activity and overall risk of prostate cancer. We conclude that recreational physical exercise is associated with reduced risk of advanced prostate cancer and prostate cancer death.

Adult↗
PubMed2006

Combined influence of early sexual maturation and central adiposity on subsequent stature. A four-year follow-up of 1,605 Norwegian boys and girls: the Young-HUNT study.

INTRODUCTION: Shorter adult stature has been attributed to early sexual maturation, as well as early adiposity, but it is not clear if these factors are interrelated. RESULTS AND DISCUSSION: A number of 1,605 Norwegian adolescents were followed from early (baseline) to late adolescence (follow-up). Maturational timing was assessed by self-reports of pubertal status (pubertal development scale, PDS) in boys and age at menarche (AAM) in girls. Height, weight and waist circumference were measured at baseline and at follow-up. Differences in height at follow-up and height gain related to the timing of sexual maturation and the level of central adiposity (i.e. high or low waist circumference) at baseline were estimated using general linear modelling. At follow-up, the median height was 180 cm in boys and 167 cm in girls. Early maturing boys and girls with relatively high central adiposity at baseline were, on average, 5.7 cm (P value<0.001) and 3.6 cm (P value<0.001) taller than early maturing boys and girls with low central adiposity. Differences in stature related to central adiposity were less pronounced for intermediate and late maturing boys and girls. The height was lowest in boys (176.6 cm) and girls (163.8 cm) who had matured early and had low central adiposity at baseline. Height gain during follow-up was independent of the level of central adiposity, but was closely related to the timing of sexual maturation. The association between the early timing of sexual maturation and subsequent height was modified by the level of central adiposity in early adolescence. CONCLUSION: The results suggest that early maturity combined with adiposity yields higher stature than early maturity and leanness.

Adiposity↗
PubMed2006

Increased risk of placenta previa in pregnancies following IVF/ICSI; a comparison of ART and non-ART pregnancies in the same mother.

BACKGROUND: The risk of placenta previa may be increased in pregnancies conceived by assisted reproduction technology (ART). Whether the increased risk is due to factors related to the reproductive technology, or associated with maternal factors, is not known. METHODS: In a nationwide population-based study, we included 845,384 pregnancies reported to the Medical Birth Registry of Norway between 1988 and 2002 and compared the risk of placenta previa in 7568 pregnancies conceived after assisted fertilization, with the risk in naturally conceived pregnancies. To study the influence of ART more directly, we compared the risk of placenta previa between consecutive pregnancies among 1349 women who had conceived both naturally and after assisted fertilization. Odds ratios (OR), adjusted for maternal age, parity, previous Caesarean section and time interval between pregnancies were estimated using logistic regression. RESULTS: There was a six-fold higher risk of placenta previa in singleton pregnancies conceived by assisted fertilization compared with naturally conceived pregnancies [adjusted OR 5.6, 95% confidence interval (CI) 4.4-7.0]. Among mothers who had conceived both naturally and after assisted fertilization, the risk of placenta previa was nearly three-fold higher in the pregnancy following assisted fertilization (adjusted OR 2.9, 95% CI 1.4-6.1), compared with that in the naturally conceived pregnancy. CONCLUSIONS: The use of ART is associated with an increased risk of placenta previa. Our findings suggest that the increased risk may be caused by factors related to the reproductive technology.

Adult↗
PubMed2006

Combined effect of blood pressure and physical activity on cardiovascular mortality.

BACKGROUND: High blood pressure increases cardiovascular mortality, but whether the effect is counteracted by physical activity is not clear. METHODS: The combined association of blood pressure and physical activity on cardiovascular mortality was assessed in a cohort of 30 597 women and 30 508 men, using standardized blood pressure measurements and information on usual frequency, duration, and intensity of physical exercise. RESULTS: During 16 years of follow-up, 1942 women and 2824 men with no history of cardiovascular disease or diabetes, who had never used blood pressure medication, died from cardiovascular causes. Cardiovascular mortality increased continuously with increasing blood pressure, and, at each blood pressure level, risk was higher in men and women with no physical activity compared with those who reported high physical activity. High activity combined with increasing pressure, however, yielded higher risk than high activity combined with normotensive pressure. Compared with the reference (systolic pressure 120-129 mmHg and high activity), the relative risk of cardiovascular death for systolic pressure of 140-159 mmHg combined with high activity was 1.21 (95% confidence interval, 0.97-1.52), compared with a relative risk of 1.73 (95% confidence interval, 1.37-2.19) in men with no activity. For women, the corresponding relative risks were 1.47 (95% confidence interval, 1.04-2.09) in the high activity group and 1.93 (95% confidence interval, 1.39-2.69) for no activity. The combined results for diastolic pressure and physical activity displayed similar patterns. CONCLUSIONS: The results support the hypothesis that cardiovascular health of individuals with moderate hypertension will benefit from regular physical exercise.

Adult↗
PubMed2006

A single weekly bout of exercise may reduce cardiovascular mortality: how little pain for cardiac gain? 'The HUNT study, Norway'.

BACKGROUND: The observation that exercise training reduces cardiovascular mortality is robust and consistent, but the amount and intensity of exercise that is required for risk reduction is not yet resolved. METHODS: We studied the association between the amount and intensity of exercise and cardiovascular mortality in 27 143 men and 28 929 women who were free from known cardiovascular disease at the beginning of follow-up between 1984 and 1986. The relative risk of death was calculated as the rate of death among participants within a given physical activity category compared with the rate of death in the reference category (no physical activity). We used Cox regression analysis to adjust for age and other potentially confounding factors. RESULTS: After 16 years (SD 4 years) of follow-up, 2946 men (10.8%) and 2486 women (8.6%) had died from ischaemic heart disease or stroke. A single weekly bout of exercise of high intensity reduced the risk of cardiovascular death, both in men [relative risk (RR) 0.61, 95% confidence interval (CI) 0.49-0.75], and women (RR 0.49, 95% CI 0.27-0.89), compared with those who reported no activity. There was no additional benefit from increasing the duration or the number of exercise sessions per week. The risk reduction related to exercise increased with increasing age in men, but not in women. CONCLUSION: These results challenge the current recommendation that expenditure of at least 1000 kcal per week is required to achieve exercise-induced protection against premature cardiovascular mortality.

Adult↗
PubMed2006

Adiposity and physical activity as predictors of cardiovascular mortality.

OBJECTIVE: To investigate whether cardiovascular mortality related to obesity could be modified by physical activity. DESIGN: Mortality follow-up. SETTING: Population study. PARTICIPANTS: Participants in a health survey: 34 868 women and 32 872 men free from known cardiovascular disease or diabetes at baseline. MAIN OUTCOME MEASURES: Total cardiovascular mortality. MAIN RESULTS: During 16 years of follow-up, 3026 women and 3526 men had died from cardiovascular causes. In middle age, obesity [body mass index (BMI) of 30 or higher] was associated with increased risk of cardiovascular death, but the association weakened with age. After 70, there was no association between BMI and cardiovascular death. At all ages, a lower level of physical activity was associated with a higher cardiovascular mortality. In women with high physical activity, indicated by at least 30 min of moderate to vigorous activity more than once a week, cardiovascular mortality was only slightly higher in the obese compared to lean women (adjusted relative risk, 1.27; 95% confidence interval, 0.80-2.00). In men with high physical activity, cardiovascular mortality was, however, significantly higher among the obese (relative risk, 1.62; 95% confidence interval, 1.09-2.40). In both genders cardiovascular mortality was substantially higher in obese people who reported no regular physical activity compared to obese people with a high level of physical activity. CONCLUSION: In obese women, being highly active may, to a large extent, compensate for the risk-increasing effect of being obese, whereas in obese men who engage in a high level of physical activity, the risk of cardiovascular death may be higher than in lean and equally active men.

Adiposity↗
PubMed2005

Recurrence of pre-eclampsia across generations: exploring fetal and maternal genetic components in a population based cohort.

OBJECTIVES: To assess the impact on risk of pre-eclampsia of genes that work through the mother, and genes of paternal origin that work through the fetus. DESIGN: Population based cohort study. SETTING: Registry data from Norway. PARTICIPANTS: Linked generational data from the medical birth registry of Norway (1967-2003): 438,597 mother-offspring units and 286,945 father-offspring units. MAIN OUTCOME MEASURES: Pre-eclampsia in the second generation. RESULTS: The daughters of women who had pre-eclampsia during pregnancy had more than twice the risk of pre-eclampsia themselves (odds ratio 2.2, 95% confidence interval 2.0 to 2.4) compared with other women. Men born after a pregnancy complicated by pre-eclampsia had a moderately increased risk of fathering a pre-eclamptic pregnancy (1.5, 1.3 to 1.7). Sisters of affected men or women, who were themselves born after pregnancies not complicated by pre-eclampsia, also had an increased risk (2.0, 1.7 to 2.3). Women and men born after pre-eclamptic pregnancies were more likely to trigger severe pre-eclampsia in their own (or their partner's) pregnancy (3.0, 2.4 to 3.7, for mothers and 1.9, 1.4 to 2.5, for fathers). CONCLUSIONS: Maternal genes and fetal genes from either the mother or father may trigger pre-eclampsia. The maternal association is stronger than the fetal association. The familial association predicts more severe pre-eclampsia.

Birth Order↗
PubMed2005

Sexual maturation in early adolescence and alcohol drinking and cigarette smoking in late adolescence: a prospective study of 2,129 Norwegian girls and boys.

Early sexual maturation has been associated with higher involvement in risk behaviour during early and mid-adolescence. In a prospective study of 2,129 girls and boys, we investigated whether the timing of sexual maturation was associated with cigarette smoking and alcohol drinking in late adolescence and whether this relation differed between boys and girls. Nine hundred and eighty boys and 1,149 girls, who participated in a cross-sectional study in middle school, were included in a follow-up study in high school 4 years later. Self-rating of pubertal status, as registered at baseline in middle school, was used to indicate the timing of sexual maturation. Age-adjusted odds ratios (ORs) with 95% confidence intervals (CIs), estimated by logistic regression, were used to assess the association between sexual maturation and alcohol drinking and daily smoking at follow-up. We found that girls who had matured early (OR 1.7, CI 1.2-2.4) or late (OR, 1.5, CI, 1.1-2.2) were both more likely to report more advanced drinking in late adolescence than were girls who were on time. Boys who had matured late were less likely (OR 0.5, CI 0.3-0.8) than boys who were on time to engage in advanced drinking. In general, daily smoking was more common among girls than boys, and more common among girls who had matured early (OR 1.5, CI 1.1-2.2) than among girls who were on time. Adjustment for social factors, e.g. parental education and marital status and parental drinking and smoking habits, did not substantially influence these results. We concluded that, for girls, but not for boys, early sexual maturation was associated with more advanced drinking and higher frequency of smoking in late adolescence. In boys, late sexual maturation was associated with reduced risk of advanced drinking.

Adolescent↗
PubMed2005

Size at birth and risk of breast cancer: prospective population-based study.

It has been hypothesized that birth size is positively associated with breast cancer risk in adulthood. We studied birth length, birth weight and head circumference at birth and subsequent risk for breast cancer in a cohort of 16,016 women in Norway. Birth length was positively associated with risk (p trend = 002), and women who were 53 cm or longer had a relative risk of 1.8 (CI = 1.2-2.6) compared with women who were shorter than 50 cm, after adjustment for birth year, length of gestation, birth order, maternal age, maternal marital status and socioeconomic status at childbearing. Mutual adjustment for birth weight did not influence the results, and further adjustment for maternal height and adult factors (age at first birth and parity) in a subset of the cohort did not change the results. For birth weight, women in the highest category (>/= 3,840 g) had an adjusted relative risk (RR) of 1.5 (CI = 1.0-2.2) compared to women in the lowest (< 3,040 g), but mutual adjustment for birth length attenuated this association (RR = 1.1; CI = 0.7-1.8). Head circumference at birth showed a similar association as birth weight, with attenuation after mutual adjustment for birth length. The positive association with birth length was stronger among women whose mothers were relatively tall (median or taller, p trend = 0.001) compared to women whose mothers were relatively short (below median, p trend = 0.67) at childbearing. The results provide evidence that intrauterine factors influence future breast cancer risk. The positive association related to birth length suggests that factors that stimulate intrauterine longitudinal growth are particularly important.

Aged↗
PubMed2005

Birth size and subsequent risk for prostate cancer: a prospective population-based study in Norway.

Studies on birth size characteristics and adult risk for prostate cancer have been few and inconclusive. We prospectively examined the association between birth size and risk for prostate cancer with particular emphasis on metastatic disease. A total of 19,681 singleton males born between 1920 and 1958, whose birth records were kept at St. Olav's University Hospital (Trondheim, Norway), were followed up for prostate cancer by linkage to the Norwegian Cancer Registry. A total of 159 cases of prostate cancer were diagnosed during follow-up; 33 had metastases at diagnosis. Overall, there was little evidence for any association between birth size and prostate cancer risk; however, there was a positive association for birth size and metastatic disease. Men in the highest quartile of birth length (> or =53 cm) had a relative risk of 2.5 (95% CI 1.0-6.3) compared to men in the lowest quartile (<51 cm). Further, men in the highest quartile of both birth weight and birth length had a relative risk of 3.8 (95% CI 1.2-12.0) for metastatic prostate cancer compared to men in the lowest category of both factors. These results support the hypothesis that factors that determine intrauterine growth could be important for aggressive forms of prostate cancer in adulthood.

Birth Weight↗
PubMed2005

The association between smoking and the prevalence of intermittent claudication.

The objective of this study was to investigate the association between smoking and the prevalence of intermittent claudication (IC). Between 1995 and 1997, all residents aged 20 years or older in Nord-Trøndelag County, Norway, were invited to take part in the Nord-Trøndelag Health Study (Helseundersøkelsen i Nord-Trøndelag: HUNT 2). A total of 19748 participants aged 40-69 years attended. Responses to 12 questions on IC (including a Norwegian translation of the Edinburgh Claudication Questionnaire) had been previously tested against the ankle-brachial pressure index (ABPI < 0.9), and an algorithm of the best test properties was used to identify people with IC. Using logistic regression analysis we computed age-adjusted prevalence odds ratios (OR) for the association between smoking and IC. Both current (ORmen = 3.8, confidence interval (CI) 2.1-6.7, ORwomen = 2.2, CI 1.4-3.4) and former smokers (ORmen = 1.7, CI 0.9-3.2, ORwomen = 1.7, CI 1.1-2.7) had a higher prevalence of IC compared with those who had never smoked, and individuals who had stopped smoking more than 20 years previously had a substantially lower prevalence of IC (ORmen = 0.2, CI 0.1-0.5, ORwomen = 0.4, CI 0.2-0.8) than current smokers. We found no association between passive smoking and IC in either men or women. Current and previous smoking habits were positively associated with the prevalence of IC, and smoking cessation was negatively associated in men and women. Passive smoking was not associated with IC in this study.

Adult↗
PubMed2005

Estimating mean sojourn time and screening test sensitivity in breast cancer mammography screening: new results.

OBJECTIVE: To assess if new screening techniques, increased use of hormone replacement therapy, or the transition from breast cancer screening trials to large scale screening programmes may influence the average time in preclinical screening detectable phase (mean sojourn time [MST]) or screening test sensitivity (STS). SETTING: Screening and interval data for 395,188 women participating in the Norwegian Breast Cancer Screening Programme (NBCSP). METHODS: Weighted non-linear least-square regression estimates using a tree step Markov chain model, and a sensitivity analysis of the possible impact by opportunistic screening between ordinary breast cancer screening rounds. RESULTS: MST was estimated to 6.1 (95% confidence interval [CI] 5.1-7.0) years for women aged 50-59 years, and 7.9 (95% CI 6.0-7.9) years for those aged 60-69 years. Correspondingly, STS was estimated to 58% (95% CI 52-64 %) and 73 % (67-78 %), respectively. Simulations revealed that opportunistic screening may give a moderate estimation bias towards higher MST and lower STS. Assuming a probable 21% higher background incidence, due to increased hormone replacement therapy use, MST estimates decreased to 3.9 and 5.0 years for the two age groups, and STS increased to 75 and 85%. CONCLUSIONS: The new estimates indicate that screening detectable phase is longer than that found in previous mammography trials/programmes, but also that the sensitivity of the screening test is lower. Overall, the NBCSP detects more cancer cases than most previous trials/programmes.

Aged↗
PubMed2004

Offspring sex and pregnancy outcome by length of gestation.

BACKGROUND: It takes a higher number of male than female embryos to produce a live born infant. The unbalanced pregnancy survival by offspring sex may also be reflected in higher proportion of preterm male births, and in unbalanced sex distribution in certain pregnancy conditions, such as preeclampsia. METHODS: We used data from the Medical Birth Registry of Norway, a population-based registry that has recorded births since 1967. For this study, we used information on offspring sex and length of gestation that was available for 1691053 (92.8%) singleton births among a total of 1822982 births from 1967 to 1998. We estimated sex ratios and perinatal mortality by length of gestation, and assessed whether the ratio of offspring sex in preeclampsia varied by length of gestation. RESULTS: For preterm births, there was a strong male dominance. Within five categories of gestational age between 16 and 36 weeks, the male/female ratios were 2.48, 1.26, 1.28, 1.32, and 1.28. At weeks 37-39, the sex ratio was 1.17, but at weeks 40-42 the number of male and female births was practically identical (sex ratio 1.00). Over all, the male/female ratio was 1.06. Perinatal mortality was consistently higher in males across the whole range of gestational age; in total it was 21% (95% CI, 18-25%) higher in male offspring. In preeclampsia with preterm delivery (<37 weeks), the sex ratio was reversed: female offspring was substantially more common than males (sex ratio 0.87), but in preeclampsia with delivery at term (37-42 weeks), the proportion of males was higher (sex ratio 1.06) than for females. CONCLUSION: The sex differences by length of gestation and in preeclampsia may reflect that male embryos are subject to stronger intrauterine selection forces than females. Possibly, implantation may be the critical event, where offspring sex may be one of the factors that determine success.

Adult↗
PubMed2004

Is pre-eclampsia more than one disease?

OBJECTIVES: The clinical characteristics of pre-eclampsia (gestational hypertension and proteinuria) may represent separate pathogenetic conditions. Pre-eclampsia accompanied by restricted fetal growth may originate from abnormal implantation, and appropriate or high birthweights may indicate a mixture of conditions, ranging from mild pre-eclampsia with modest placental involvement to hypertensive conditions without placental disease. DESIGN: Prospective, observational study. SETTING: General population. POPULATION: We used data from the Medical Birth Registry of Norway, a population-based registry that has recorded births since 1967. For this study, we used information on length of gestation and presence of pre-eclampsia among 1,679,205 singletons born between 1967 and 1998. Pre-eclampsia was diagnosed in 44,220 (2.6%) pregnancies. METHODS: We studied the risk of pre-eclampsia in relation to standardised measures (z scores) of birthweight, adjusted for length of gestation, and stratified by term and preterm delivery. We also explored whether gestational diabetes was more prevalent in conjunction with preterm than term pre-eclampsia. MAIN OUTCOME MEASURES: Pre-eclampsia diagnosed at term or preterm. RESULTS: For pre-eclampsia diagnosed around term, there was a U-shaped association with birthweight. Compared with appropriate birthweights for gestation, the risk of term pre-eclampsia was more than fourfold higher (relative risk [RR] 4.5, 95% confidence interval [CI], 4.3 to 4.7) if the baby's birthweight was lower than two standard deviations under the mean. For birthweights three standard deviations or higher than the mean, pre-eclampsia was more than twice as likely (RR 2.6, 95% CI 2.2-2.9). In contrast, the risk of preterm pre-eclampsia displayed an L-shaped association with birthweight. Low birthweight (less than -2 standard deviations) was associated with greatly increased risk (RR 9.9, 95% CI 9.1-10.9), but for high birthweights (>or=3 standard deviations), there was no association with the risk of preterm pre-eclampsia (RR 1.2, 95% CI 0.7-2.1). The prevalence of gestational diabetes was three times (prevalence ratio 3.3, 95% CI 2.6-3.6) higher in preterm than term pre-eclampsia. CONCLUSION: Whereas pre-eclampsia with preterm delivery associated with low birthweight may be caused by underlying placental abnormality, pre-eclampsia delivered at term may represent a mixture of conditions, ranging from mild pre-eclampsia with moderate placental affection to hypertensive conditions in pregnancy without placental dysfunction.

Adult↗
PubMed2003

[Change of partner between births and adverse pregnancy outcomes].

BACKGROUND: Childbearing with different fathers has increased in western societies because of the higher frequency of divorce and remarriage. Pregnancy outcomes may differ between mothers who have changed partner between first and second birth and mothers who have the same father for both births. Women who change partner may have individual characteristics that increase risk of adverse outcomes, but change of partner could also be associated with unfavourable changes in behaviour. MATERIAL AND METHODS: The Medical Birth Registry of Norway was established in 1967 and includes information on approximately 1.8 million births until 1998. Both parents are recorded. We have compared pregnancy outcomes for 30 176 mothers who changed partner between first and second birth and 461 154 mothers who had the same partner for both births. RESULTS: In relation to the first birth, the risk of adverse pregnancy outcomes was not clearly different between mothers who later had a second birth with another partner and mothers who had the same partner for both births. Offsprings of mothers who changed partner between first and second birth were at higher risk of infant mortality (relative risk 1.5, 95 % confidence interval, 1.3-1.7), preterm birth (< 37 weeks; relative risk 1.3, 95 % confidence interval, 1.2-1.4), and low birth weight (< 2500 gram; relative risk 1.5, 95 % confidence interval, 1.4-1.6), after adjustment for maternal age and level of education, interval between births, and time period. INTERPRETATION: Mothers who change partner between first and second birth are at increased risk of having a preterm, low birth weight baby with increased risk of infant death for the second child compared to mothers who have the same partner for both births.

Birth Order↗
PubMed2003

Effects on pregnancy outcome of changing partner between first two births: prospective population study.

OBJECTIVE: To compare the effects on pregnancy outcomes of changing partner between the first two births with having the same partner for both births. DESIGN: Prospective population study. SETTING: Norway. PARTICIPANTS: 31 683 women who changed partner between their first two births and 456 458 women with the same partner for both births. RESULTS: After adjustment for maternal age and education, interval between births, and decade of birth, the risk of adverse pregnancy outcomes for the second birth was higher for women who changed partner between the first two births compared with those who had the same partner for both births: preterm birth (< 37 weeks; relative risk 2.0, 95% confidence interval 1.9 to 2.1), low birth weight (< 2500 g; 2.5, 2.3 to 2.6), and infant mortality (1.8, 1.6 to 2.1). For the first birth, the risk of these adverse pregnancy outcomes was only slightly higher for mothers who subsequently had a second birth with another partner. CONCLUSION: Women who change partner between their first two births are at an increased risk of delivering a preterm, low birthweight baby with an increased risk of infant mortality compared with women who have the same partner for both births.

Birth Order↗