Oh, dear! my friend and I have children whose birthdays are days apart. We planned a joint party last year and had to change the date once. Her mom is from Korea and according to their culture, you must have the party on or before the b-day. Otherwise, it is bad luck. I have a friend who is German and she says the custom there is to have it on or after the actual day, otherwise, it is bad luck.
As far as I'm concerned, you are what you believe and the universe brings you what you need. Pray, think, hope, meditate--whatever you want to call it for a safe pregnancy and delivery for the mom and baby and pick up your needles.
And, remember, sometimes bad things do happen but it's not because you knit a baby sweater.