it may just mean you are not as far along as you thought. the dates are just an estimate based on the start date of your last period. you could be up to two weeks less in which case the would only see a fetal pole or implantation site. you should have your levels checked to see if they increase and another ultrasound to see if it changes. a lot of times when it is early in a pregnancy things do not always show up right away. these tests are not infallible do not worry!
This is the birth sac that needs to be removed so the baby can start to breathe. If you are talking about the sac that shows on an ultrasound, this is the amniotic sac that contains the 'waters' and is absolutely necessary for the growth of the baby. It is the same thing that the answer above mentions.
at about 4 weeks they can sometimes see the gestation sac. by 5 weeks they can usually see the yolk sac. and by 6 weeks you can usually see a fetal pole, sometimes even a heartbeat
What is a Blighted Ovum (Empty Gestational Sac)? A blighted ovum (empty gestational sac) occurs when a fertilized egg implants into the uterine wall, however, the fetus does not continue to develop past the sixth to eighth week of gestation. There is continued development of the placenta and amniotic sac which produces hCG (giving the positive pregnancy test). Most women either do not know they are pregnant or find out within the first trimester that they have a blighted ovum (empty gestational sac).
I had a ultrasound scan at 7 weeks 3 days, and the pregnancy sac was visible, but my doctor could not find the fetal pole or heartbeat. He said there can be a significant amount of dvelopment from week 7 to 8, and I sm scheduled for another scan in a week's time. He said this wasn't necessarily bad news so I'll just have to wait.
placenta
That it's probably too early. I would recommend a followup ultrasound at 7 weeks.
are membrane that helps
Sounds normal. Congratulations!
this is called the placenta
It is normal for the sac and the placenta to come out with each puppy. It is also normal for the mother to EAT the sac and the placenta.
Identical twins do not share a sac during pregnancy. They each have their own amniotic sac and placenta.
no