The traumatic losses of miscarriages are greatly undermined culturally, especially given how many women have experienced them. Conversations around grief often center death and breakups, and erase the complicated space miscarriages take up - a death of someone you were eagerly waiting to meet.
Since miscarriages are so common, and affect up to 50% of pregnancies (although many occur before the woman is aware of the pregnancy), a lot of couples don't announce their pregnancies until the first trimester is finished, to lower the chances of publicly grieving a miscarriage.
There are obvious upsides to keeping a pregnancy secret at first: you have time to process the news, you have time to prepare answers to the slew of questions that follow, and you can avoid being put in a position to share bad news if the pregnancy goes south.
The downside, however, is that when you lose a pregnancy before it's been announced you end up carrying a minefield of grief around that other people are unaware of.