This study uses German data, but also argues that the "climate anxiety" reason is weakly associated with parenthood: www.demogr.mpg.de/en/news_even...
demogr.mpg.de
MPIDR - Worried About the Environment, but Still Becoming Parents
Decades of German data suggest that strong environmental concerns generally did not delay or deter parenthood, while such worries tended to fade with age among parents and non-parents alike. Whether today’s youngest generations, growing up with climate change as a constant reality, will follow the same pattern remains an open question.