I am 43 got pregnant naturally after trying for 18 months. When I missed my period I went to the doc, had one u/s and they foung two sacs one with 4 weeks heart beating and the another was empty, no heart beat though. I got a second u/s today 7 weeks according to my period. Still have two sacs, one with 7w+2 days with heart beating, the another one 6w+1day with heat beating. Is it normal. Thank you!
The doctor bases the age of the fetus on its size. Twins don't share the same sac; when you deliver them, you deliver them one at a time, not together. One twin is always bigger than the other, hence the different 'ages'. It's just an estimate and nothing to get upset about. If the twins are identical, a single egg was fertilized and later split into two. If you are pregnant with fraternal twins they were probably conceived within 24 hours of one another, not a full week.