Could a miscarriage be seen as a type of birth control?
The answer is "yes" and "no"! It can also be worse... it could also be considered an act of abortion.
It depends on the intention of the mother. If the intention is to cause a miscarriage to terminate the pregnancy then it is abortion. If the intention wasn't there then the mother may be off the hook (on the judgment day). IMO
After realizing she is pregnant - if a pregnant mother purposely makes her body toxic for the fetus by doing everything against common sense or doctor's advice or if she fails from doing things needed to be done to support the pregnancy - then it is a form of abortion in my opinion. For example - if the mother intentionally continue smoking and taking drugs or alcohol - when she is aware that she is pregnant or if she purposefully starves herself (not eat enough) or don't stay hydrated and as a result she experiences a miscarriage then it is abortion. IMO
As a host - the mother's body needs to be a safe haven and it needs to do everything to facilitate the pregnancy. The growing fetus has certain nutritional requirement, so the mother needs to eat food that can provide all that is needed. If the mother purposely tries to survive through an unbalanced diet then chances are the fetus will "let go" at a earlier stage - because it cannot acquire all that it needs to grow.
So, the intention of the mother is the key!
However, if you are judging by earthy laws then it may be very difficult to prove the mother made a conscious decision to make her body inhabitable. In that case it cannot be called abortion with certainty. But I believe on the judgment day - it will be very easy for God to judge her through her intentions. Since I believe our body is like computers and we are all connected to God's server and everything we do is being uploaded. In some religions - it says that on the judgment day - our own hand, eyes, mouth, every part of our body will testify against us! All intentions will be reviewed. God's judgment will be extremely fair for all parties involved... it will be extremely just! IMO
When a miscarriage happens due to unforeseeable reasons and without the intention of the pregnant mother - then it is simply a miscarriage with (probably) no consequence to the mother on the judgment day. IMO