Adult nursing is general looking after patients with personal care, medications etc.
Midwives are looking after expecting mothers to be and delivering the baby when it's ready to come in to the world 🌎. There's lots more to midwifery than adult nursing, you have to learn about everything about how the woman's body changes and prepare for pregnancy.
If nurses and midwives were taught the same, then they wouldn't be seperate professions. Student midwives are taught how to be midwives - how to care for expectant mothers. Student adult nurses are taught how to be adult nurses - how to care for patients aged 18+ in specialities other than midwifery