Heian period:

The Fujiwara controlled the throne until the reign of Emperor Go-Sanjo (1068-1073), the first emperor not born of a Fujiwara mother since the ninth century. Go-Sanjo, determined to restore imperial control through strong personal rule, implemented reforms to curb Fujiwara influence. He also established an office to compile and validate estate records with the aim of reasserting central control. Many shoen were not properly certified, and large landholders, like the Fujiwara, felt threatened with the loss of their lands. Go-Sanjo also established the In-no-cho (ja: Office of the Cloistered Emperor), which was held by a succession of emperors who abdicated to devote themselves to behind-the-scenes governance, or insei.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". Who was the last emperor born to a Fujiwara mother?
unanswerable