Correlation between getting pregnant while breastfeeding and miscarriage?

I’ve been researching a lot about the chances of getting pregnant while breastfeeding. (Trying to decide if I need to get on birth control or will breastfeeding be enough)

And a lot of women who say they got pregnant while breastfeeding follow up with they lost the baby in a miscarriage.

Anyone know if there is a correlation between the two?

Maybe because breastfeeding causes your uterus to contract? I’m no doctor I’m just wondering.