Final answer:
The client with a history of previous thromboembolism is at most risk for the development of postpartum thromboembolic disorders.
Step-by-step explanation:
The client most at risk for the development of postpartum thromboembolic disorders is one with a history of previous thromboembolism. This history significantly increases the risk of future thromboembolic events, including those that may occur in the postpartum period. Other factors that could contribute to an increased risk include advanced maternal age, as indicated by the data showing an increased incidence of fetal anomalies with maternal age; however, between the options provided, a history of thrombosis stands out as the primary risk factor for thromboembolic disorders.