1 Kings 15:1-2 Now in the eighteenth year of king Jeroboam the son of Nebat reigned Abijam over Judah. Three years reigned he in Jerusalem. And his mother's name was Maachah, the daughter of Abishalom. "
2 Chronicles 13:1-2 Now in the eighteenth year of king Jeroboam began Abijah to reign over Judah. He reigned three years in Jerusalem. His mother's name also was Michaiah the daughter of Uriel of Gibeah. And there was war between Abijah and Jeroboam."
This apparent contradiction about the references to the mother of Abijam or Abijah rests essentially on a lack of understanding and overview of the families mentioned and their genealogies. Furthermore, the same person is called by different names. We already see that Abijam and Abijah are two slightly different names are used for the same person, i.e. for the king who began to reign in Jerusalem.
In 1 Kings 15 Abijam's mother is called "Maacha", which means "suppression"; in 2 Chronicles however, she is called "Michaiah", which means "Who is like Jehovah?". Michaiah is the name which is used for her as the queen mother, Maacha is the name which is used in connection with her idolatry (cp. 2 Chronicles 15:16).
Abijam's (Abijah's) mother is once called the "daughter of Abishalom" and once the "daughter of Uriel of Gibeah". According to Josephus (Ant. VIII,10.1), this Uriel was the husband of Abishalom's daughter Tamar, and Tamar then was the mother of Maacha. Maacha was therefore not literally the real "mother" of Abijam, but rather the word "mother" is used by means of the figure of speech Synecdoche (of species) for a female ancestor. She was in reality the grandmother of Abijam, but she is mentioned here in the record about the beginning of Abijam's reign because of her position and her influence at the royal court.