liam muir answered 6/19/2010 How Long Are Guppies Pregnant? I have guppies and I have 11 guppies 5 males and 6 females I have had 2 for 3 months and it had 5 frys and they were dead the next day now today I bought 9 and some were pregnant I think there pregnant for 4-5 weeks. Hope it helps.