I'm pleased you're leaning towards waiting a year. I've been doing a physics degree with the OU for the past few years (it's not called physics anymore, can't remember what it is called now, but it's changed it's name twice in the last few years). In that time I've had 2 pregnancies and babies & I've really struggled keeping up with work.
Both pregnancies were difficult, with multiple issues & several hospital stays. Luckily I wasn't studying too much when I was pregnant - got pregnant with DC1 while studying, did exam at 23 weeks, a week before first hospital stay in premature labour.
DC1 was premature in the end & had lots of medical issues so I didn't study at all until he was older. Then got pregnant with DC2, was expecting nightmare pregnancy, which it was, so no studying when pregnant. However, I was forced by the OU to study a module beginning in early Feb - DC2 was due mid-Feb but was born early Jan. I tried so hard to do that module, but ended up deferring it for a year.
I hated the way I had to palm my newborn off on anybody who would take her so I could study. I hated the fact I would watch her for any sign of tiredness so I could try & get her to sleep so I could study. I was missing being with her as a newborn & hated myself for it. I was also struggling badly with post-natal depression & was actually admitted to hospital with it. Plus, I had the realisation that even if I made all these sacrifices, due to sleep deprivation, pnd & other factors I wouldn't do as well in the course as I could do. All that effort for just a pass, or even a fail, instead of a 2:1.
You're young, you've got time! I would rather look back on enjoying my baby - lots of cuddles & laughing - rather than forego that for studying. It's a cliche but it's true - they do grow up so fast.
I would also do research on the OU. For my degree course the quality of the course has gotten worse every year, and it really is awful now. I would certainly not recommend the OU for physics/physical science/natural science/whatever they're calling it now.