Clinical Features Between Primary Obstetric Antiphospholipid Syndrome and Non‐Criteria Obstetric Antiphospholipid Syndrome and Risk Factors of Adverse Pregnancy Outcomes: A Retrospective Study of 1006 Cases

ABSTRACT Problem To compare the clinical characteristics and pregnancy outcomes between patients with primary obstetric antiphospholipid syndrome (OAPS) and those with primary non‐criteria obstetric antiphospholipid syndrome (NC‐OAPS), and to identify the risk factors of adverse pregnancy outcomes in both groups. Methods A retrospective single‐center study was performed in a university hospital of western China, including 141 patients with OAPS and 865 patients with NC‐OAPS. The clinical characteristics, pregnancy complications, and obstetric outcomes of the cohorts were collected from the hospital system and were compared by univariable analysis, and the independent risk factors for adverse pregnancy outcomes (APO) were investigated by logistic regression analysis in these two populations. Results The OAPS patients had a significantly higher risk for stillbirths compared to the NC‐OAPS patients, while the NC‐OAPS group had a significantly higher risk for preterm birth and overall APO. Double aPL positivity, triple aPL positivity, and gestational hypertension were the independent risk factors for APO in OAPS patients, whereas two of the double aPL positivity subtypes, triple aPL positivity and placenta previa were independent risk factors for APO in NC‐OAPS patients. Conclusion This study identified different rates in different APOs among OAPS and NC‐OAPS patients. Additionally, this study revealed different risk factors for the development of APO between the two populations. These findings indicated that OAPS and NC‐OAPS are two distinct entities of the same disease, providing new insights into the individualized management for patients with OAPS and NC‐OAPS.