Even the Bible itself cannot even define the proper definition of a pregnancy or when a life becomes a life inside the womb.
It wasn't until the advances in medicine and science that trimesters, fetal growth, and other such indicative terms to define a pregnancy and how it develops were even brought to light.
The Bible even states several passages on abortion as if it could care less if a woman loses her child. See for yourself:
Abortion is not murder. A fetus is not considered a human life.
If men strive, and hurt a woman with child, so that her fruit depart from her, and yet no mischief follow: he shall be surely punished, according as the woman's husband will lay upon him; and he shall pay as the judges determine. And if any mischief follow, then thou shalt give life for life. -- Exodus 21:22-23
The Bible places no value on fetuses or infants less than one month old.
And if it be from a month old even unto five years old, then thy estimation shall be of the male five shekels of silver, and for the female thy estimation shall be three shekels of silver. -- Leviticus 27:6
Fetuses and infants less than one month old are not considered persons.
Number the children of Levi after the house of their fathers, by their families: every male from a month old and upward shalt thou number them. And Moses numbered them according to the word of the LORD. -- Numbers 3:15-16