I'm nearly 25 weeks in and I've just realised I have no idea how much longer I'll be in this trimester. Some sites say the 2nd trimester is weeks 13 - 26 and some say it's 13 - 28. So do we move over in week 27 or week 29 or somewhere in-between? Also, most people I know refer to the 20 week scan as the 5 month scan, because there's more or less 4 weeks in a month and 4 * 5 = 20. But 5 weeks on I'm still only 5 months pregnant - I don't reach six months until week 26 (because there's really 4.4 weeks in a month; 52 weeks in 12 months = 26 weeks in 6). But if 26 weeks = 6 months, shouldn't that be the start of the third trimester? Argh. My brain hurts. Month 5 has been the longest month ever. Edit: Just noticed this site says it's 13 - 26 and 27 - birth. I'll go with that.