Association Between Preconception Hemoglobin Level And Low Birth Weight Outcome In Women Of Childbearing Age In Yunnan Province And Zhejiang Province

Objective:In recent decades,extensive research,both domestically and internationally,has been conducted to investigate the impact of hemoglobin levels during pregnancy on adverse pregnancy outcomes.However,the majority of these studies have primarily focused on the influence of pregnancy-related anemia,and there remains a lack of consensus regarding the relationship between pre-pregnancy hemoglobin levels and adverse pregnancy outcomes.Moreover,limited research has been conducted on the association between altitude and hemoglobin levels in relation to the occurrence of low birth weight.Therefore,the aim of this study is to comprehensively analyze and explore the correlation between preconception hemoglobin levels and the risk of low birth weight in women of reproductive age.Specifically,the study will examine the association between preconception anemia,elevated hemoglobin levels,and the risk of low birth weight,while accounting for the altitude factor.By investigating the combined effects of preconception hemoglobin levels and altitude,this study seeks to enhance our understanding of the outcomes related to low birth weight.Methods:This study employed a retrospective cohort design based on the National Free Pre-Pregnancy Checkups Project(NFPCP).It focused on women of reproductive age(18-49 years)in Yunnan and Zhejiang provinces,with pregnancies occurring between January 2014 and December 2015.A total of67,938 eligible women were included,while cases with missing data,multiple births,and induced abortions were excluded.Pre-pregnancy hemoglobin levels were categorized into three or five groups,adjusted for altitude above 1000 meters.Logistic regression and restricted cubic spline estimation assessed the association between pre-pregnancy hemoglobin levels and the risk of low birth weight.Participants were also divided into low and high altitude groups to explore the combined effects of altitude and hemoglobin levels on the outcome.Results revealed an overall low birth weight incidence of 1.32%,with the highest incidence observed in the moderate to severe anemia group.Pre-pregnancy anemia accounted for 7.41% of the total population,while the high hemoglobin group accounted for 3.12%.After adjusting for multiple factors,the moderate to severe anemia group exhibited a 72% increased risk of low birth weight compared to the normal hemoglobin group.The analysis indicated a slight U-shaped relationship between pre-pregnancy hemoglobin levels and the risk of low birth weight.Furthermore,the high altitude group with moderate to severe anemia had an 88% increased risk compared to the low altitude group with normal hemoglobin levels.In summary,the incidence of low birth weight in this study was 1.32%(897 cases)overall,with variations observed across different provinces.Pre-pregnancy anemia and high hemoglobin levels were associated with an increased risk of low birth weight.The findings underscore the importance of preconception hemoglobin screening and altitude consideration in developing preventive strategies to enhance maternal and infant health outcomes.Conclusion:In women of reproductive age,there is a U-shaped relationship between preconception hemoglobin levels and the risk of low birth weight(LBW).Moderate to severe anemia(hemoglobin < 100 g/L)prior to pregnancy significantly increases LBW risk.Residential altitude interacts with preconception hemoglobin levels,especially in regions ≥ 1000 m,where anemia further raises LBW risk.It is recommended for Chinese regions to develop altitude-specific preventive measures.Strengthening preconception hemoglobin screening and early monitoring,along with appropriate interventions,can reduce LBW incidence and improve maternal-infant health.