Testosterone is classified as a category D/X drug based on research by the companies who make it, indicating risk of fetal malformations. It is unlikely to ever be studied further given the ethical risks of a potential teratogenic drug being deliberately given in a trial.
https://www.drugs.com/pregnancy/testosterone.html
Of course, there should be no need for a female to be on testosterone during a pregnancy.
It was Sally Hines et al who argued that wanting healthy fetuses not exposed to the potential teratogenic effects of exogenous testosterone was akin to eugenics, in wanting to guarantee “healthy” babies:
Ultimately, we argue that in the context of lacking and uncertain medical evidence (HRT with testosterone during pregnancy and chest feeding) in a highly gendered treatment context (pregnancy and lactation care), both patients and providers tend to pursue precautionary, offspring-focused treatment approaches. These approaches reinscribe binarized notions of sex, resulting in social control in their attempts to safeguard against non-normative potential future outcomes for offspring. These offspring-focused risk-avoidance strategies and approaches are, we argue, part of the gendered precautionary labor of pregnancy and pregnancy care itself, and not without potentially-harmful consequences for trans people and society more broadly.
https://www.sciencedirect.com/science/article/pii/S2667321523000811?via%3Dihub