What was the significance of MM giving birth to Michitsuna so quickly after her marriage in The Kagero Diary: A Woman’s Autobiographical Text from Tenth-century?

The fact that she had Michitsuna exactly nine months after her marriage revealed that her unwilling marriage to Fujiwara had become sexual almost immediately. This suggested, along with his frequent abandonment of her after the birth of their child, that Fujiwara had married MM primarily because of his physical attraction to her.