Because of this Shaap of Umaa to Devtaa, ie celestials, Devtaa cannot have children from their wives. They have to use some other medium to have a child. We have many examples of this in our history - 

--Hanumaan was the son of Pavan (Wind) Dev;
--Punjikaasthalee Apsaraa had Hanumaan from Pavan Dev
--Menakaa Apsaraa had her daughter Shakuntalaa from Vishwaamitra Jee [although Apsaraa are not Devtaa but this applies to them also]
--Urvashee Apsaraa had six sons from Pururavaa
--Somadaa had Brahmdatt from Rishi Choolee
--All six Paandav were the children of Soorya Dev (Karn), Dharm Raaj (Yudhishthir), Pavan Dev (Bheem), Indra (Arjun), and Ashwinee Kumaar (Nakul and Sahadev) respectively.

Another Shaap she gave to Earth. The sin of Earth was to bear the semen of Shiv Jee onto her surface. That the appearance of earth will not be uniform and in quality (for it has lands and oceans, deserts and forests, volcanoes and mountains, ice and humidity, etc). And she will be the wife of many - so the Earth is also the official wife of numerous kings.