<p>Wide applications of nanomaterials cause substantial environmental impacts and public concerns over their toxicity when they are intentionally (such as in medicine) or unintentionally (environment exposure) introduced into the human and animals. As a susceptible population, pregnant women are particularly vulnerable to nanoparticle-induced toxicity. However, research in this aspect is still limited and many reported findings are often inconsistent even under the “similar” experimental conditions. Here, we discuss some controversial issues which impeded further progress in this research area. Issues in the discussion are crucial effects of nanoparticles’ true identity in a physical, chemical, or biological context, and the delicate effects of gestational stages during the pregnancy.</p>