i went for my first scan 3 weeks ago and i had no idea how far along i was and they couldnt see anything, i went back a week later and they ruled out ectopic because of my levels and they could now see a gestational sac, measuring 4.1mm, i have just been for a scan today and they can now see a yolk sac measuring 2mm, but no heartbeat and the gestational sac has only grown to 6.6mm, is this normal? everything i am reading says its not. i have to wait a week to go back but welcome any advice..... thanks
If you are very early in pregnancy only seeing a sac would be normal. You cannot see anything more than that until you are 6+ weeks, and you are not sure when you conceived. I wouldn't say you are going to miscarry, the only thing you can do is wait and see and let nature do it's thing. I would just try not to google every little thing... even though I know it's hard I do it all the time too. But, there is a good possibility everything could be just fine and it's just to early to see more.
Gestational Sac (4 weeks)
The gestational sac is the earliest sonographic finding in pregnancy. The gestational sac appears as an echogenic (bright echoes) ring surrounding a sonolucent (clear) center. The gestational sac does not correspond to specific anatomic structures, but is an ultrasonic finding characteristic of early pregnancy. Ectopic pregnancies can also have a gestational sac identified with ultrasound, even though the pregnancy is not within the endometrial cavity.
The gestational sac first appears at about 4 weeks gestational age, and grows at a rate of about 1 mm a day through the 9th week of pregnancy.
Your ability to identify an early gestational sac will depend on many factors, including the capabilities of the ultrasound equipment, your approach (vaginal or abdominal), your experience, the orientation of the uterus (generally it is easier to see if the uterus is anteflexed or retroflexed), and the presence of such complicating factors as fibroid tumors of the uterus. While a gestational sac is sometimes seen as early as during the 4th week of gestation, it may not be seen until the end of the 5th week, when the serum HCG levels have risen to 1000-1500 mIU.
Gestational sac size may be determined by measuring the largest diameter, or the mean of three diameters. These differences rarely effect gestational age dating by more than a day or two.
1st Trimester Ultrasound Scan
Yolk Sac ( 5 weeks)
As the pregnancy advances, the next structure to become visible to ultrasound is the yolk sac. This is a round, sonolucent structure with a bright rim.
The yolk sac first appears during the fifth week of pregnancy and grows to be no larger than 6 mm. Yolk sacs larger than 6 mm are usually indicative of an abnormal pregnancy. Failure to identify (with transvaginal ultrasound) a yolk sac when the gestational sac has grown to 12 mm is also usually indicative of a failed pregnancy.
Yolk sacs that are moving within the gestational sac ("floating"), contain echogenic material (rather than sonolucent), or are gross misshapen are ominous findings for the pregnancy.
Fetal Heart Beat
Using endovaginal scanning, fetal cardiac activity is often seen even before a fetal cell mass can be identified. The fetal cardiac muscle begins its' rhythmic contractions, and that rhythmic motion can be seen along the edge of the yolk sac. Initially, the fetal cardiac motion has a slower rate (60-90 BPM), but cardiac rate increases as the fetus develops further. Thus, for these early pregnancies, the actual cardiac rate is less important that its presence or absence.
Sometimes, with normal pregnancies, the fetal heartbeat is not visible until a fetal pole of up to 4 mm in length is seen. Failure to identify fetal cardiac activity in a fetus whose overall length is greater than 4 mm is an ominous sign.
It can sometimes be difficult identifying a fetal heartbeat from the background movement and maternal pulsations. You may find it useful in these cases to scan with one hand while taking the maternal pulse with the other. This makes it easier to identify sonographic movements that are dyssynchronous with the maternal pulse.
Fetal Pole (6 weeks)
A mass of fetal cells, separate from the yolk sac, first becomes apparent on transvaginal ultrasound just after the 6th week of gestation. This mass of cells is known as the fetal pole. It is the fetus in its somite stage. Usually you can identify rhythmic fetal cardiac movement within the fetal pole, although it may need to grow several mm before this is apparent.
The fetal pole grows at a rate of about 1 mm a day, starting at the 6th week of gestational age. Thus, a simple way to "date" an early pregnancy is to add the length of the fetus (in mm) to 6 weeks. Using this method, a fetal pole measuring 5 mm would have a gestational age of 6 weeks and 5 days.
Crown Rump Length
This term is borrowed from the early 20th century embryologists who found that preserved specimens of early miscarriages assumed a "sitting in the chair" posture in both formalin and alcohol. This posture made the measurement of head-to-toe length impossible. Instead, they subsituted the head-to-butt length (crown rump length) as a reproducible method of measuring the fetus.
Early ultrasonographers used this term (CRL) because early fetuses also adopted the sitting in the chair posture in early pregnancy. Today, the crown rump length is a universally recognized term, very useful for measuring early pregnancies. The CRL is highly reproducible and is the single most accurate measure of gestational age. After 12 weeks, the accuracy of CRL in predicting gestational age diminishes and is replaced by measurement of the fetal biparietal diameter.
In at least some respects, the term "crown rump length" is misleading:
For much of the first trimester, there is no fetal crown and no fetal rump to measure.
Until 53 days from the LMP, the most caudad portion of the fetal cell mass is the caudal neurospone, followed by the tail. Only after 53 days is the fetal rump the most caudal portion of the fetus.
Until 60 days from the LMP, the most cephalad portion of the fetal cell mass is initially the rostral neurospore, and later the cervical flexure. After 60 days, the fetal head becomes the most cephalad portion of the fetal cell mass.
What is really measured during this early development of the fetus is the longest fetal diameter.
From 6 weeks to 9 1/2 weeks gestational age, the fetal CRL grows at a rate of about 1 mm per day.
Determination of Gestational Age
Measurement of the gestational sac diameter or the length of the fetal pole (CRL) can be used to determine gestational age. Charts have been developed for this purpose, but some simple rules of thumb can also be effectively used.
Gestational Sac: Gestational age = 4 weeks plus (mean sac diameter in mm x days). This relies on the growth of the normal gestational sac of 1 mm per day after the 4th week of gestation. For example, a gestational sac measuring 11 mm would be approximately 5 weeks and 4 days gestational age. (4 weeks plus 11 days = 5 weeks and 4 days).
Crown Rump Length: Gestational age = 6 weeks plus (CRL x days). This relies on the growth of the normal fetus of 1 mm per day after the 6th week of gestation. For example, a CRL of 16 mm would correspond to a gestational age of 8 weeks and two days (6 weeks plus 16 days = 8 weeks and 2 days).
hope this helps and that you get goog news on your next ultrasound.
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