There is a lot of information about my own pregnancies I would not want shared. Add in the personal stuff about how you told family (and how they reacted - "My dear, it's your fourth, have you considered termination?") and I really do not think this is appropriate.
I think back to what I know about my own arrival (and the stuff I know and the fact that I DO know is a worry also, when you think about it). My mother thought she had reached menopause when her periods stopped. And some weight gain is normal in menopause. She already had seven kids and copped flak for it even though bigger families were more acceptable back then. But she had had to get married and so was perhaps extra sensitive to the "can't you two stop doing it?" comments from her family.
She was six months pregnant with me when she went to the doctor for a check-up. "I'm guessing it's menopause," she told him. Was horrified when told she was pregnant, told nobody. Her own parents were dead, her in-laws were still critical. Told my dad of course, and probably the eldest kids. Visited her in-laws the week before I was born, they did not realise she was pregnant and she did not tell them. I don't know what she expected. MAybe she was saying nothing in case things went wrong and she came home without a baby.
Despite all this, she did tell me that she enjoyed raising me more than the others, because I came so much later and she felt a lot more confident as a parent by then. She felt more relaxed about what to do. I did tire her out more, but she also had older kids to palm me off onto, which helped.
But if I had had to share this info with my class - not acceptable. My mother would have been horrified that we were asked.
Before you get too negative about the teacher, find out where the topic has come from. In our country, the Board of Studies sets the curriculum and teachers have to abide by it. There is some rubbish in there (such as half the Grade 8 Geography course being about "global change"). Then have a go at whoever is responsible for setting such an unteachable topic.
Go to the source.
Marg