pregnant women can't lift hands above head according to MIL?? :/

I understand not lifting something heavy over your head, but at my baby shower yesterday I was hanging up a banner (so very light lol) and my MIL told me off and said that it's not good for pregnant women to put their hands up above their head or stretch with their hands up, because apparently it can cause the umbilical cord to tighten and if it's around baby's neck at that point in time, well.... I've never heard of this and know my MIL can be quite dramatic and likes to make a fuss, but should I be listening to this piece of advice? I just think surely my midwife or OB would have warned me against this if it was a legitimate risk :/