It is not possible to have a gestation sac without the baby, since the sac is a group of cells that separated from the ovule to create the sac. However, something might be something wrong with your glands, thus the low HCG level.
It is possible to see a uterine sac, called a pseudo sac, with an ectopic pregnancy, but most likely there will be nothing in the uterus.
Gestation means pregnancy.
a synonym for gestation is pregnancy
Gestation is used for animal, but pregnancy use for human.
This is called the gestation period in mammals, and pregnancy in humans.
pregnancy
Gestation, or a gestation period.
about the size of a pea
Cows pregnancy is closest to a human pregnancy by number of gestation days . Cow gestation roughly 9 1/2 months. Human gestation roughly 9 months
Identical twins do not share a sac during pregnancy. They each have their own amniotic sac and placenta.
Gestation
Pregnancy