A nested case-control study of factors influencing adverse pregnancy outcomes in women with previous pregnancy loss

Abstract Recurrent pregnancy loss is common in women of childbearing age and also causes great physical and psychological harm to patients and families, but the relationship between the number of previous miscarriages and the risk of adverse pregnancy outcomes in subsequent pregnancies is unclear. The purpose of this study is to provide clinical data to support whether the number of previous pregnancy losses increases the risk of adverse pregnancy outcomes in women with a history of previous pregnancy losses. We conducted a cohort-based, nested case-control study and recruited 1074 women with a history of pregnancy loss. Detailed demographic and medical history information was collected at baseline, and biological specimens were retained for laboratory testing. Adverse pregnancy outcomes (APOs) were chosen as the primary outcome indicator, with cases being defined as individuals who experienced any APOs events. Cases were matched with event-free control subjects at a 1:2 ratio. We used conditional logistic regression to examine the relationship between the number of previous pregnancy losses and APOs events, using age at first pregnancy as the reference exposure. We identified 358 cases with APOs events and 716 controls. The occurrence of APOs was associated with an increased number of previous pregnancy loss exposures compared to controls without APOs (OR: 1.36; 95% CI: 1.14 to 1.61), which persisted after considering patient demographics, total number of previous pregnancy history, and other exposures (aOR: 1.75; 95% CI: 1.28 to 2.4). In addition, we found that age at first pregnancy within a certain range may also be a risk factor for APOs.