Gadolinium‐based complex contrast agents (GBCAs), frequently applied in magnetic resonance imaging (MRI), are associated with severe acute anaphylactic shock and incurable nephrogenic systemic fibrosis. Besides, the repeated use of GBCAs may result in the accumulation in various tissues. Given these potential adverse effects, GBCAs have not been well used during pregnancy. Herein, a novel metal‐free T2‐weighted MRI nanoprobe, designated fluorinated small‐sized graphene oxide with optimized fluorine content (LF‐sGO), is developed via graphene oxide materials. By introducing specific polar C─F bonds onto the small‐sized graphene oxide (sGO) skeleton, the prepared nanoprobe exhibits excellent water solubility, as well as superior MRI capabilities, thereby furnishing high‐resolution MRI anatomical information. Furthermore, the free radicals on LF‐sGO stabilized by C─F bonds confer LF‐sGO enrichment in the tumor region, enabling comprehensive imaging capability. The cytotoxicity study in vitro indicates that LF‐sGO has the potential to serve as a biocompatible imaging probe. Moreover, detailed in vivo studies on pregnant mice and zebrafish adequately demonstrate that microinjection of LF‐sGO does not induce dysontogensis and teratogenesis. This study successfully showcases a metal‐free nanoprobe that exhibits exceptional MRI capabilities for the purpose of tumor diagnosis. Notably, this nanoprobe holds promise for safe and effective tumor diagnosis during pregnancy.