The second fetus may have been terminally underdeveloped, and small enough to be delivered without realizing it was a second baby. They may have told her there was no second baby or that it was part of the afterbirth, or she may have misunderstood what they said.

Doctors have been known to lie to patients in the past, but the practice is not very common anymore in most cultures.

Because my mother has never lied to me. So why would she lie about something like this?

That's how im sure about it. So if there's any misinformation about it, it's not from my mother. The doctors, maybe, but not my mother