true, the follicle has to mature & be released into the f-tubes before it can be fertilized.
now, a lot more eggs (ova) do get fertilized than the zygote (fertilized egg) actually implants within the uterine wall.
maybe only a quarter implant, & of that well less than half survive the first couple/few weeks.
the odds are truly against any single zygote surviving through that first 6 weeks!
its also interesting to note that more than half of all pregnancies begin as twins,
...with only one surviving in most cases thru the 1st tri.
my alyssa is well above average health & fitness, & so have the fathers been,
...so it doesn't surprise me that she's successfully had twins ore than once.