My Bounty book says that it's not good to lie on back from 24 weeks - why??

[horseshoe]

I am 36 weeks and this seems to be the only way I can sleep at the moment. Is there some sort of medical reason you shouldn't lay on back?

I think it creates pressure and can lead to breathlessness and light headedness.
But the discomfort has to be weighed against needing to sleep.

Sleep on your back if you need to. Sit on a birth abll during day and scrub floors

I was told by my NCT teacher that there is some vital artery (vital to the mother) going up behind the bump, and that after the bump gets to a certain weight it can restrict blood flow, leading, as Slur says, to dizzyness.

But if it't not causing a problem for you I am presuming it's not a problem - speak to your midwife if you're worried?

Do you have one of those long pregnancy pillows? I thought they were a terrible gimmick at the start of my pregnancy and was in love with mine by the end.

I believe it could cut off the supply to the baby as the weight of the baby could squash the umbilical cord????. I went for a check up at 38 weeks and lay on my back to hear the heartbeat. It was slow, so slow even I could tell. My midwife was great, didn't panic and told me to roll on my side. The heartbeat immediately sped up to normal. She still sent me to the hosp for monitoring.
But if it was that bad and that common they wouldn't get you to lie on your back for monitoring at all would they.
I think it is a 'recommendation' that is all.
The best way to lie is on you left side I believe. Helps position the baby in theory.

I had the dizziness thing once in my first pregnancy when I'd been lying a bit too flat. It was horrible! If you are well propped up with pillows though you should be ok. I think the problem is most likely to be with the weight of the placenta etc pressing down on your aorta rather than on the baby though?

It does make more sense that it would affect you and not the baby as other posters have put...

I do wish these books would put the reason in though! With dd1 - where I did lie on my back one night with aforementioned unpleasant dizzy results - I had no idea - I thought it might be in case you got stuck and couldn't get up

I thought it had to do with the blood supply to the baby being reduced due to baby pressing on a major artery (and nothing to do with umbilical cord which is cushioned inside). It used to make me feel really sick and dizzy.

It is the artery (vena cava??) I thought. Surely where the umbilical cord is depends on the position of the baby & placenta so wouldn't be the same for everyone. Whereas everyone has a major artery down their back.

The weight of the uterus can press on a blood vessel, reducing cardiac output and therefore affecting blood supply to placenta. Nothing to do with squashing placentas or umbilical cords...although babies can (and do) lie on or squeeze cords.

Used to have the most blissful sleep on my back when heavily pregnant though! So, hey..

We ask you to lie (or tilt)on to your left side because the vena cava lies behind the uterus, slightly to the right. When you lie flat on your back, it compresses the vena cava, this can slow the baby's heartbeat (until you move) as it restricts bloodflow, similarly it makes you dizzy and/or slightly breathless. Thats why if the baby's heartbeat ever seems slow, we automatically ask you to lie towards your left!

Hoorah! Answers from people who know

Thank you, Left hand side tonight it is then!

Agree with NL, book should explain a bit more.

Glad to help!!