In Midianite culture, the men didn't get circumcised until they were engaged. They would get circumcised, recuperate, marry and then consummate the marriage. This being said the son was most likely not old enough in Midian culture to get circumcised. They didn't circumcise the men at 8 days old as Abraham's covenant required.
In reply to How about this. Zipporah by Regina
In Midianite culture, the men didn't get circumcised until they were engaged. They would get circumcised, recuperate, marry and then consummate the marriage. This being said the son was most likely not old enough in Midian culture to get circumcised. They didn't circumcise the men at 8 days old as Abraham's covenant required.