Centene Corporation withdrew its 2025 earnings guidance following an early analysis of data from the Affordable Care Act (ACA) marketplace that revealed higher morbidity and slower growth than anticipated. This led to a reduction in net risk adjustment revenue by approximately $1.8 billion, resulting in an estimated $2.75 per share earnings per share (EPS) hit. The withdrawal caused Centene's shares to plunge as much as 40%, marking the largest single-day drop since 2006 and closing at an eight-year low. The market reaction also affected other health insurers such as Humana, Cigna, Oscar Health, and Molina Healthcare, which saw declines in sympathy. Analysts from JPMorgan and Jefferies downgraded Centene's stock and lowered price targets, citing unexpected risks and slower growth in ACA exchanges across 22 states. The ACA risk-adjustment program's zero-sum nature means Centene's losses reflect broader market challenges. Molina Healthcare subsequently lowered its full-year adjusted EPS guidance to a range of $21.50 to $22.50 from a prior forecast of $24.50, citing medical cost pressures across all lines of business and reporting preliminary Q2 adjusted EPS of approximately $5.50, below consensus estimates. S&P is reportedly considering downgrading Centene's credit rating to junk status due to the suspended profit outlook and ongoing cost pressures. The developments highlight increasing financial challenges for health insurers operating in the ACA marketplace amid rising medical costs and enrollment uncertainties.