The dose-response relationship of pre-menopausal alcohol consumption with age at menopause: a population study of 280 497 women in Norway.

BACKGROUND: Previous research suggests that alcohol consumption is associated with high age at menopause. Yet, knowledge about the dose-response relationship is inconsistent. Thus, we studied the pattern of the association of pre-menopausal alcohol consumption with age at natural menopause. METHODS: We performed a retrospective population-based study using self-reported data from 280 497 women aged 50-69 years attending the Norwegian breast cancer screening programme (BreastScreen Norway) during 2006-15. Associations of weekly alcohol consumption between the age of 20 and 49 years with age at menopause were estimated as hazard ratios (HRs) using Cox proportional hazard models with restricted cubic splines to allow for non-linear associations. We adjusted for year and place of birth, number of childbirths, educational level, body mass index and smoking habits. RESULTS: Mean age at natural menopause was 51.20 years (interquartile range: 49-54 years). The adjusted HR of reaching menopause was highest for women with no alcohol consumption (reference) and the HR decreased by alcohol consumption up to 50 grams per week (adjusted HR 0.87; 95% CI: 0.86-0.88). Above 50 grams, there was no further decrease in the HR of reaching menopause (P for non-linearity of <0.001). CONCLUSIONS: Women who did not consume alcohol were youngest at menopause. The lack of a dose-response association among alcohol consumers implies virtually no relation of alcohol consumption with age at menopause. Our findings may suggest that characteristics of the women who did not consume alcohol, not accounted for in the data analyses, explain their younger age at menopause.

The relation of number of childbirths with age at natural menopause: a population study of 310 147 women in Norway.

STUDY QUESTION: Does age at natural menopause increase with increasing of number of childbirths? SUMMARY ANSWER: Age at menopause increased with increasing number of childbirths up to three childbirths; however, we found no further increase in age at menopause beyond three childbirths. WHAT IS KNOWN ALREADY: Pregnancies interrupt ovulation, and a high number of pregnancies have therefore been assumed to delay menopause. Previous studies have had insufficient statistical power to study women with a high number of childbirths. Thus, the shape of the association of number of childbirths with age at menopause remains unknown. STUDY DESIGN, SIZE, DURATION: A retrospective population study of 310 147 women in Norway who were 50-69 years old at data collection. PARTICIPANTS/MATERIALS, SETTING, METHODS: The data were obtained by two self-administered questionnaires completed by women attending BreastScreen Norway, a population-based screening program for breast cancer. The associations of number of childbirths with age at menopause were estimated as hazard ratios by applying Cox proportional hazard models, adjusting for the woman's year of birth, cigarette smoking, educational level, country of birth, oral contraceptive use and body mass index. MAIN RESULTS AND THE ROLE OF CHANCE: Women with three childbirths had the highest mean age at menopause (51.36 years; 95% CI: 51.33-51.40 years), and women with no childbirths had the lowest (50.55 years; 95% CI: 50.48-50.62 years). Thus, women with no childbirths had higher hazard ratio of reaching menopause compared to women with three childbirths (reference group) (adjusted hazard ratio, 1.24; 95% CI: 1.22-1.27). Beyond three childbirths, we estimated no further increase in age at menopause. These findings were confirmed in sub-analyses among (i) women who had never used hormonal intrauterine device and/or systemic menopausal hormonal therapy; (ii) women who were born before 1950 and (iii) women who were born in 1950 or after. LIMITATIONS, REASONS FOR CAUTION: Information about age at menopause was based on self-reports. WIDER IMPLICATIONS OF THE FINDINGS: If pregnancies truly delay menopause, one would expect that women with the highest number of childbirths had the highest age at menopause. Our results question the assumption that interrupted ovulation during pregnancy delays menopause. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the South-Eastern Norway Regional Health Authority [2016112 to M.S.G.] and by the Norwegian Cancer Society [6863294-2015 to E.K.B.]. The authors declare no conflicts of interest. TRIAL REGISTRATION NUMBER: N/A.

The association of birthweight with age at natural menopause: a population study of women in Norway.

BACKGROUND: Previous studies suggest that birthweight may influence age at natural menopause, but the evidence remains inconclusive. Thus, we aimed to estimate the association of birthweight with age at natural menopause. METHODS: A retrospective population study of 164 608 women in Norway, aged 48-71 years. Data were obtained by two self-administered questionnaires among participants in BreastScreen Norway during 2006-2014. We used Cox proportional hazard models to estimate hazard ratios and logistic regression models to estimate odds ratios of menopause according to birthweight. Restricted cubic splines were applied to allow for possible non-linear associations, and adjustments were made for year and country of birth. RESULTS: Women with birthweight <2500 g were median 51 years at menopause (interquartile range 49-54 years), whereas women with birthweight 3500-3999 g were median 52 years at menopause (interquartile range 49-54 years). The hazard ratio of menopause decreased with increasing birthweight up until 3500 g. At birthweights >3500 g, we estimated no further decrease (P for non-linearity = 0.007). Birthweight at 2500 g increased the odds ratios of menopause before the age of 45 [1.20; 95% confidence interval (CI): 1.14-1.25] and the age of 40 (1.26; 95% CI: 1.15-1.38) compared with birthweight at 3500 g. At birthweights 4000 g and 4500 g, the odds ratio estimates were very similar to the reference group and the CIs overlapped 1.00. CONCLUSIONS: We found a non-linear dose-relationship of birthweight with age at natural menopause, and low birthweight was associated with early natural menopause. Our findings suggest that growth restriction during fetal life may influence the timing of natural menopause.

Exercise in pregnancy: an association with placental weight?

BACKGROUND: Women with high levels of physical exercise have an increased demand for oxygen and nutrients. Thus, in pregnancies of women with high levels of exercise, it is conceivable that the supply of oxygen and nutrients to the placenta is suboptimal, and growth could be impaired. OBJECTIVE: The objective was to study the association of frequency of exercise during pregnancy with placental weight and placental to birthweight ratio. STUDY DESIGN: This was a prospective study of 80,515 singleton pregnancies in the Norwegian Mother and Child Cohort Study. Frequency of exercise was self-reported by a questionnaire at pregnancy weeks 17 and 30. Information on placental weight and birthweight was obtained by linkage to the Medical Birth Registry of Norway. RESULTS: Placental weight decreased with increasing frequency of exercise (tests for trend, P < .001). For nonexercisers in pregnancy week 17, the crude mean placental weight was 686.1 g compared with 667.3 g in women exercising ≥6 times weekly (difference, 18.8 g; 95% confidence interval, 12.0-25.5). Likewise, in nonexercisers in pregnancy week 30, crude mean placental weight was 684.9 g compared with 661.6 g in women exercising ≥6 times weekly (difference, 23.3 g; 95% confidence interval, 14.9-31.6). The largest difference in crude mean placental weight was seen between nonexercisers at both time points and women exercising ≥6 times weekly at both time points (difference, 31.7 g; 95% confidence interval, 19.2-44.2). Frequency of exercise was not associated with placental to birthweight ratio. CONCLUSION: We found decreasing placental weight with increasing frequency of exercise in pregnancy. The difference in placental weight between nonexercisers and women with exercising ≥6 times weekly was small and may have no clinical implications.

Exercise level before pregnancy and engaging in high-impact sports reduce the risk of pelvic girdle pain: a population-based cohort study of 39†184 women.

OBJECTIVE: To examine whether an association exists between exercise levels pre-pregnancy and pelvic girdle pain in pregnancy. Pelvic girdle pain in pregnancy has been associated with physical inactivity, a risk factor for adverse pregnancy outcomes. METHODS: We used data from a population-based cohort study including 39 184 nulliparous women with a singleton pregnancy enrolled in the Norwegian Mother and Child Cohort study. Pre-pregnancy exercise frequency and types were assessed by questionnaire in pregnancy week 17. Pelvic girdle pain, defined as combined pain in the anterior pelvis and in the posterior pelvis bilaterally, was self-reported in pregnancy week 30. Multivariable Poisson regression estimated risks of pelvic girdle pain associated with pre-pregnancy exercise. We examined a dose-response association of prepregnancy exercise frequency using restricted cubic splines. A test for non-linearity was also conducted. Final models were adjusted for pre-pregnancy BMI, age, education, history of low back pain and history of depression. RESULTS: 4069 women (10.4%) reported pelvic girdle pain in pregnancy and the prevalence among women who were non-exercisers prepregnancy was 12.5%. There was a non-linear association for pre-pregnancy exercise and risk of pelvic girdle pain (test for non-linearity, p=0.003). Compared to non-exercisers, women exercising 3-5 times weekly pre-pregnancy had a 14% lower risk of developing pelvic girdle pain in pregnancy (aRR 0.86, 95% CI 0.77 to 0.96). Taking part in high-impact exercises such as running, jogging, orienteering, ballgames, netball games and high-impact aerobics were associated with less risk of pelvic girdle pain. SUMMARY: Women who exercise regularly and engage in high-impact exercises before the first pregnancy may have a reduced risk of pelvic girdle pain in pregnancy.

Mode of delivery and persistence of pelvic girdle syndrome 6 months postpartum.

OBJECTIVE: We sought to study the association between mode of delivery and persistent pelvic girdle syndrome (PGS) (pain in anterior and bilateral posterior pelvis) 6 months postpartum. STUDY DESIGN: We followed up 10,400 women with singleton deliveries in the Norwegian Mother and Child Cohort Study who reported PGS in pregnancy week 30 (1999 through 2008). Data were obtained by 3 self-administered questionnaires and linked to the Medical Birth Registry of Norway. RESULTS: Planned cesarean section was associated with the presence of severe PGS 6 months postpartum (adjusted odds ratio [OR], 2.3; 95% confidence interval [CI], 1.4-3.9). In women who used crutches during pregnancy, emergency (adjusted OR, 2.0; 95% CI, 1.0-4.0) and planned (adjusted OR, 3.3; 95% CI, 1.9-5.9) cesarean section were each associated with severe PGS. CONCLUSION: The results suggest an increased risk of severe PGS 6 months postpartum in women who underwent a cesarean section vs women who had an unassisted vaginal delivery.

Pelvic girdle pain in pregnancy: the impact of parity.

OBJECTIVE: The purpose of this study was to estimate the association of parity with pelvic girdle syndrome (PGS; pain in anterior and bilateral posterior pelvis). STUDY DESIGN: We included 75,939 pregnant women in the Norwegian Mother and Child Cohort Study. Data were obtained by self-administered questionnaires. RESULTS: By pregnancy week 30, 15% of the women had developed PGS. Among first-time mothers, 11% of the women reported PGS, compared with 18% of the women with 1 previous delivery and 21% of women with 2 previous deliveries. The odds ratios for PGS of having had 1 or 2 previous deliveries were 1.9 (95% confidence interval [CI], 1.9-2.0) and 2.4 (95% CI, 2.3-2.6), respectively, after adjustment for other study factors. For PGS with severe pain, the corresponding odds ratios were 2.6 (95% CI, 2.3-2.9) and 3.8 (95% CI, 3.3-4.3). CONCLUSION: The risk of the development of PGS increased with number of previous deliveries, which suggests that parity-related factors play a causal role.