I had a 28 week scan today because at 22 weeks my placenta was noted as marginal previa (under 20 mm from cervix). It was 2 mm away from my cervix then. Today, at 28 weeks, my cervix is still only 3 mm away. I'm really worried. Anyone know, at this late stage if the uterus will expand enough to pull my placenta at least 20 mm from my cervix? 20 mm I'm told is the minimum distance before they will allow me a natural birth. My next scan is in 4 weeks at 32 weeks. What is the likelihood it will shift between now and then? P.s. I am really grateful however that my baby is growing beautifully. Just want a normal birth with no stress on him.