InterLACE Study Team (2019) Variations in reproductive events across life: a pooled analysis of data from 505 147 women across 10 countries. Human Reproduction, 34 (5). pp. 881-893. ISSN 0268-1161
Abstract
STUDY QUESTION
How has the timing of women’s reproductive events (including ages at menarche, first birth, and natural menopause, and the number of children) changed across birth years, racial/ethnic groups and educational levels?
SUMMARY ANSWER
Women who were born in recent generations (1970–84 vs before 1930) or those who with higher education levels had menarche a year earlier, experienced a higher prevalence of nulliparity and had their first child at a later age.
WHAT IS KNOWN ALREADY
The timing of key reproductive events, such as menarche and menopause, is not only indicative of current health status but is linked to the risk of adverse hormone-related health outcomes in later life. Variations of reproductive indices across different birth years, race/ethnicity and socioeconomic positions have not been described comprehensively.
STUDY DESIGN, SIZE, DURATION
Individual-level data from 23 observational studies that contributed to the International Collaboration for a Life Course Approach to Reproductive Health and Chronic Disease Events (InterLACE) consortium were included.
PARTICIPANTS/MATERIALS, SETTING, METHODS
Altogether 505 147 women were included. Overall estimates for reproductive indices were obtained using a two-stage process: individual-level data from each study were analysed separately using generalised linear models. These estimates were then combined using random-effects meta-analyses.
MAIN RESULTS AND THE ROLE OF CHANCE
Mean ages were 12.9 years at menarche, 25.7 years at first birth, and 50.5 years at natural menopause, with significant between-study heterogeneity (I2 > 99%). A linear trend was observed across birth year for mean age at menarche, with women born from 1970 to 1984 having menarche one year earlier (12.6 years) than women born before 1930 (13.5 years) (P for trend = 0.0014). The prevalence of nulliparity rose progressively from 14% of women born from 1940–49 to 22% of women born 1970–84 (P = 0.003); similarly, the mean age at first birth rose from 24.8 to 27.3 years (P = 0.0016). Women with higher education levels had fewer children, later first birth, and later menopause than women with lower education levels. After adjusting for birth year and education level, substantial variation was present for all reproductive events across racial/ethnic/regional groups (all P values < 0.005).
LIMITATIONS, REASONS FOR CAUTION
Variations of study design, data collection methods, and sample selection across studies, as well as retrospectively reported age at menarche, age at first birth may cause some bias.
WIDER IMPLICATIONS OF THE FINDINGS
This global consortium study found robust evidence on variations in reproductive indices for women born in the 20th century that appear to have both biological and social origins.
STUDY FUNDING/COMPETING INTEREST(S)
InterLACE project is funded by the Australian National Health and Medical Research Council project grant (APP1027196). GDM is supported by the Australian National Health and Medical Research Council Principal Research Fellowship (APP1121844).
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © The Author(s) 2019. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. This is an author produced version of an article published in Human Reproduction. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | reproductive events; age at menarche; first birth; age at menopause; number of children |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Food Science and Nutrition (Leeds) > FSN Nutrition and Public Health (Leeds) The University of Leeds > Faculty of Medicine and Health (Leeds) > School of Medicine (Leeds) > Leeds Institute of Cardiovascular and Metabolic Medicine (LICAMM) > Clinical & Population Science Dept (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 10 Jan 2019 13:56 |
Last Modified: | 05 Mar 2020 01:38 |
Status: | Published |
Publisher: | Oxford University Press |
Identification Number: | 10.1093/humrep/dez015 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:140840 |