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In Japan, only women are eligible to take the national midwife exam.
Literal
Japan [in-では] midwife national-exam [genitive-の] taking-eligibility [topic-は] women only [into-と] has-become.
A plain-stated factual sentence. ~のみ is the formal/written equivalent of ~だけ ('only,' 'just X'), most often found in legal, bureaucratic, or expository writing. The predicate ~となっている ('has become X,' 'is officially set as X') is a formal/written way of stating an official status or arrangement — common in institutional or legal descriptions. The compound noun 助産師国家試験 ('midwife national exam') is another good example of Sino-Japanese compound stacking: 助産師 (midwife) + 国家 (national) + 試験 (exam). Note that 助産師 replaced the older gendered 助産婦 in official usage.