UnitedHealth Group (UNH) saw its stock price plummet by 5.01% during Wednesday's trading session, as the health insurance sector faced a widespread selloff triggered by Centene's unexpected withdrawal of its 2025 earnings forecast.

The turmoil began when Centene announced late Tuesday that it was pulling its full-year financial guidance due to lower-than-expected revenue from its health insurance marketplace plans. This news sent shockwaves through the industry, causing a domino effect on other major health insurers. Centene's own shares plunged by nearly 40%, while other companies in the sector also experienced significant declines.

UnitedHealth, as one of the largest players in the health insurance market, was not immune to this sector-wide panic. The company's stock had already been under pressure in recent months due to rising medical costs and reported investigations into its billing practices. This latest development has further eroded investor confidence in the short term, despite UnitedHealth's strong market position and long-term growth prospects.

Analysts suggest that the issues faced by Centene, particularly in the Affordable Care Act marketplace plans, could have broader implications for the industry. There are concerns about the potential for similar challenges across other insurers, including UnitedHealth, related to marketplace growth and higher-than-expected medical costs. As the market digests this news, investors will be closely watching for any signs of similar trends in UnitedHealth's upcoming financial reports.