A 31-year-old Gravida 5 Para 2 Live 2 Abortion 2, without comorbidities, underwent spontaneous vaginal delivery at term. She was asymptomatic in postpartum and had puerperal sterilization under low risk on postnatal day 4. After fourteen hours of surgery, she experienced an acute onset of breathlessness, tachypnea, and orthopnoea. Workup revealed right-sided pleural effusion filling three-fourths of the cavity with consolidation on chest X- ray. Therapeutic thoracocentesis was performed draining 600 ml of straw-coloured fluid. She was started on the Piperacillin tazobactam combination. Due to the repeated collection and persistent symptoms, a continuous intercostal drain was placed after 4 days. Due to persistent fever spikes, antibiotics were stepped up to Linezolid and Meropenem. A negative result on the Mantoux test, CBNAAT, and IGRA test was obtained. ANA profiling revealed the presence of non-specific KU antibodies. Symptomatic improvement was noted, and the ICD was subsequently removed after 6 days of insertion. Pregnancy is an immunosuppressive state. Rapid reversal of this state in postpartum results in a flare-up of quiescent infection. Even auto-immune diseases flare up in postpartum. Understanding this phenomenon of immune reconstitution syndrome and its impact will help in the management planning of postpartum women without dilemmas.