The right answer is Child abuse.
Cannabis (marijuana) during pregnancy is dangerous for the fetus
During pregnancy, the active component of cannabis, which is THC (tetrahydrocannabinol), can go into the placenta and affect the fetus, including its birth weight (like the case in the question here) and brain function, reducing the baby's IQ and attention capacity.
Depending on the type of drug and the quantity consumed, it is also possible that the baby suffers from weaning at birth, that is to say from deprivation (inconsolable crying, irritability, tremors, feeding difficulties, etc.). .
Cannabis may also have longer-term effects in children (learning disabilities, behavioral problems, hyperactivity, etc.).
Natural selection refers to the phenomenon by which the species in a population possessing the tendency to get adapted in a condition enhance in numbers in comparison to those who exhibit fewer adaptation capacities over a number of generations.
In other words, it can be stated as the non-random and differential development of distinct genotypes function to sustain favorable variant and to eradicate less favorable variants. Some of the conditions are required for the process of natural selection to take place.
These are heredity, reproduction, variation in individual characters, and variation in the fitness of organisms among the members of the population. If the conditions are met, then the phenomenon of natural selection occurs by default.