怀孕要几个月？

朋友：“ei..怀孕到底是几个月啊？9个月还是10个月？”
生小螃蟹的日子就刚好和我的预产期差一天，非常的准
所以每一次要回答这问题前，我一定要再算一次怀小螃蟹时到底是几个月

在网上看到了这问题的标准答案

 (转自Babycentre.com)
Isn't a month four weeks long?
Actually, the only month that's four weeks (or 28 days) long is February – that is, when it's not a leap year. All the others are either 30 or 31 days. So, on average a month is 30.4 days long – or 4.3 weeks.