The association between the maternal pre-pregnancy platelet count and fecundability in mainland China:a population-based cohort study

Background: Currently, awareness about platelet count (PC) and its consequences for perinatal outcome have increased, but there is little reliable evidence on fecundability.Methods: Based on the National Free Pre-conception Check-up Projects supported by the Chinese government, 5,524,886 couples met the inclusion criteria were included in this cohort study. Cox regression models were adopted to estimate fecundability ratios (FRs) and their 95% confidence intervals for pre-pregnancy PC quintiles. Restricted cubic splines were used to flexibly model and visualize the relationship of PC with FRs. Microsoft SQL server and R software were used for data management and analysis.Results: The median of pre-pregnancy PC among women was 221.00x10(9)/L. The first (<177.00 x10(9)/L) and second quintile (177.00-207.99 x10(9)/L) of PC showed slightly increased fecundability (Q1: adjusted FR 1.05, 95% CI 1.04-1.06; Q2: adjusted FR 1.04, 95% CI 1.03-1.05), while higher quintals (Q4: 236.00-271.99 x10(9)/L; Q5: >= 272.00 x10(9)/L) were related to reduction of fecundability, when compared with the third quintile of PC (208.00-235.99 x10(9)/L) (Q4: adjusted FR 0.96, 95% CI 0.95-0.97; Q5: adjusted FR 0.88, 95% CI 0.87-0.89). In the first quintiles (<177.00x10(9)/L), only 20.93% women had PC below 129.94x10(9)/L. An inverse-U shape association was consistently observed among women such that the lower PC of normal range (<118.03x10(9)/L) and higher PC (>223.06x10(9)/L) were associated with the risk of reduced female fecundability (P for non-linearity < 0.01).Conclusion: PC is associated with female fecundability. Further classification of PC levels may deepen our understanding of the early warnings and significance of female fecundability.