Later on a pregnancy test comes back positive, an ultrasound washed effectually half-dozen weeks subsequently your final menses can provide the side by side clue every bit to how everything's progressing in there. While yous won't be able to see much yet, there's a skillful chance that yous'll spot a 3- to 5-millimeter circle almost the size of a pencil eraser on the screen.

This is known as the yolk sac, and information technology's key to learning if your pregnancy is developing the style it should in its early on stages.

What is the yolk sac?

The yolk sac is office of the gestational sac, the protective covering that surrounds a developing baby and contains the amniotic fluid. It appears nigh a week or two after the embryo has implanted in the uterus (during week 4), and information technology disappears near the stop of the first trimester.

During that time, the yolk sac provides all the nutrients a little embryo needs. It also produces carmine claret cells until the placenta fully forms and takes over.

When should you see the yolk sac on an ultrasound?

Y'all should see the yolk sac when y'all go for your outset ultrasound, typically between weeks 6 and 9 of pregnancy.

The gestational sac is technically visible before that, effectually the fourth or fifth week. It looks like a round construction in your uterus that's 2 to 3 millimeters in bore, and it increases by well-nigh a millimeter each day early on in the pregnancy.

About a calendar week later, the yolk sac has grown enough to announced on an ultrasound too. It'll await like a round, dark mass with a bright rim measuring simply a few millimeters around. Like the gestational sac, it will go bigger over the next few weeks. By the x-calendar week mark, a yolk sac volition typically measure out a (still tiny!) half-dozen millimeters.

What if there'south no yolk sac during a six-week ultrasound?

If the yolk sac isn't visible at your six-week ultrasound, you lot may feel scared and confused. But information technology's also possible that you got your dates wrong and your pregnancy isn't equally far along as you lot idea.

This is specially truthful if y'all have less-than-regular menstrual cycles. That's why your practitioner will likely send y'all home and have you come back in a week or 2 to see what's going on. Most of the time, you'll be greeted with the sign of a gestational sac (and possibly even a fetal heartbeat!).

Sometimes, yet, the technician tin meet a yolk sac, but it doesn't look correct. This tin point a trouble with the pregnancy and portend a miscarriage — merely futurity healthy pregnancies are still very much possible. Signs include:

  • An irregular shape (wrinkled with indented walls)
  • Calcifications in the yolk sac that brand it harder to see through
  • A yolk sac that'due south smaller than two millimeters or greater than v millimeters
  • A yolk sac that appears to be moving within the gestational sac

Does an empty gestational sac mean miscarriage?

If the gestational sac is still empty at a follow-up appointment, then it'southward what'due south known as a fated ovum, or anembryonic pregnancy. This type of miscarriage occurs when an embryo never develops or stops developing. The most common reason this happens is because of a chromosomal abnormality, and the odds of a future healthy pregnancy remain very expert.

Nigh of the fourth dimension, an anembryonic pregnancy occurs then early on that you lot wouldn't even know almost it unless you were keeping an heart on the calendar, which many hopeful moms-to-be are.

You can take a blighted ovum and even so feel pregnancy symptoms like sore breasts, nausea and vomiting. This is considering the early on embryo all the same secretes a pregnancy hormone — human chorionic gonadotropin (hCG) — until information technology stops developing.

With a blighted ovum, a doctor volition most likely advise watching and waiting for a couple weeks. If your body recognizes that an embryo isn't developing, information technology will miscarry the contents with bleeding similar to a heavy period. Just if information technology doesn't, a medical provider may prescribe a medication that induces bleeding. He or she may besides recommend a brief surgical procedure (a D&C) to empty the uterus.

The yolk sac is a positive sign and an of import indicator of pregnancy health. If you see it, it's reassurance that all is well and your fiddling asset is starting to develop equally expected. But fifty-fifty if one'southward absent or irregular correct now, the odds are still proficient that y'all'll successfully conceive once more and give birth to a healthy baby.