There is no law that states at what age a girl may get pregnant.
There are laws in effect to limit the age that individuals can have sex with "minors"
Even these laws are being lessened depending on the age difference between partners, how consensual it is, how long the relationship has been, etc.
Most states in the USA have what is known as "Romeo and Juliet" laws that take this into effect.
But there is no longer that makes it illegal for a female to get pregnant at any age. In other words, the pregnant female will not be charged for becoming pregnant no matter what her age is.
Now morally and emotionally and practically wrong?
Well you didn't ask that, so I won't answer
It depend on the legal age of consent in the said country. If 16 is the legal age of consent in the said country, then it's not legally wrong to be pregnant at 16. But if the legal age of consent in the said country is 18, then the person that got the girl pregnant will be in trouble should the girl's family decide to report the incident to the authority.
18 years is the constitutional legal age of consent in my country and as a result, any man that gets a girl below 18 pregnant regardless of whether the girl consented or not, will be in great trouble should the girl's family report him to the police.