It may be concluded, therefore, that on a low plane of nutrition, the foetus lives as a parasite, the tissues of the foetus having a prior claim on the nutrients circulating in the maternal blood stream.
https://www.cambridge.org/core/services/aop-cambridge-core/content/view/FE3C75CA91EF14B39FE4419B107241E5/S0029665169000085a.pdf/the-foetus-as-a-parasite.pdf