Sheikh Shaker Elsayed, a prominent Muslim scholar, explains the following regarding Islam and polygamy:

The issue of polygamy needs explanation. I hope to help you understand it.

First, some facts about polygamy:

1- Polygamy existed well before Islam.
2- Islam did not start this institution.
3- It existed in all cultures, civilizations and times.
4- Polygamy was unlimited and unconditional.
5- A Man was able to marry and divorce at whim.
6-A Man had all the rights and a woman had none.
7- There were no limitations on the number of women a man could marry at the same time.

Here is what Islam did:

1- Restricting this institution to a maximum of four women.
2- Setting conditions for justice and fairness to the process and to the relationship to these wives.
3- Instituting women rights in details that did not exist before in any culture, religion or civilization.
4- It gave women the right of refusal to participate in such marriage by including this as a condition in the marriage contract. This in fact happened in the case of Fatimah, the Daughter of the Prophet (peace and blessings be upon him).
5- It compelled men to use it wisely and only as needed.

Circumstances that warrant polygamy as a matter of reality:

1- Existence of widows and orphans, as mentioned in the first couple of Ayat in Surat Al-Nisaa’ as a result of wars, which are still raging in many countries, or natural death.
2- In cases where a woman does not have as much desire for sexual activities, while the husband desires more, but they still love each other and want to keep the marriage. It is better to keep the marriage than break it to establish a new one that may end up like the first case.
3- If the couple have children, but they are also having problems in their live as a couple. Marrying another wife, may help their situation, as they both take a break from each other, while still care for the kids together as a joint responsibility.
4- Cases of women who do not marry at young to moderate age, do not normally attract young men who may prefer young women, but they, these women, may have a chance to marry a married man, and live happy with them.
5- Any woman who does not like her marriage situation has the Islamic right to seek divorce and get it, even when she does not have hurt or harm complaints to support her claim. The mere fact that she does not want to be in a polygamous relationship is enough to secure her divorce under Islamic law.