I want to know if Omugwo, a situation where a mother-in-law from the wife's side goes to assist her for some period of time immidiately after childbirth, if it is only practice here in Nigeria.

Do white mother-in-laws go for for Omugwo?

Before nko? All races and cultures practice it. A new mother would not know how to handle a newborn and might kill it via one of many mistakes.

If there is no mother alive any older female relative with experience can take their place. Alot of older females with child bearing knowledge in one or both families are readily available.

its an Igbo not Nigerian thing...if its Nigerian, then other ethnic nationalities would be practicing it