There's also the one that if you don't have sex much in the 1st trimester then the baby is early, again, another myth. I was practically frog-marching DH into the bedroom in the last month or so and he really is fantastic, but it did nothing for me (well, I suppose it kept me happy about being overdue). However, I had a 40-hour labour with 6 hours of pushing (I had a feeling about six hours, sadly I thought that was going to be labour length) and wasn't quite as happy about that.
I've just realised that you're Mama of 2 that was, Cricket... ha, you can change your name but you can't hide from me forever!
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