Doctor insights on:
Gestational Age Vs Fetal Age
Minor: Gestational age refers to the length of time since the first day of your last period. Fetal age refers to the age of your developing baby, counting from the estimated date of conception. ...Read more
With an ultrasoundn is fetal age always 2 weeks smaller then gestational age? What about if you have irreg cycles? Are these taken into consideration
No: Ultrasounds determine actual measurements but its measurement is not different from that by last menstrual period. If there is 2 week difference it may be acceptable in late pregnancy since ultrasound measurements lose precision later in pregnancy. Early pregnancy ultrasounds if done correctly are very accurate and 2 week difference may be related to uncertain period date. ...Read more
Gestational age.: All obstetrical care by convention is based on estimated gestational age (ega) - not actual embryonic/fetal age. A first trimester ultrasound can pinpoint your due date with great accuracy. ...Read more
Why are fetuses measured by gestational age and not by the actual fetal age? So if u are 12wks the measurements are actually of a 10 week old fetus?
Math: Gestational age is based on your last period. The best way we can estimate fetal age....After doing thousands of measurements standards have emerged...So if you are 12 weeks and the baby is 10 weeks in size, it would indicate a smaller baby at this time...Just a way to follow growth of the baby. If I am off, I hope an OB wills set the record straight. ...Read more
Likely gestational: Most of the time pregnancy is described in terms of gestational age. This is of historical relevance because prior to the invention of imaging technologies the most reliable mark of timing of pregnancy was the first day of the last menses. Ovulation occurs 14 days thereafter on the average. So fetal age is two weeks less than the menstrual or gestational age. ...Read more
Both: Fetal age is of course the exact age of your fetus as determined by measurements taken of the baby. Fetuses have different rates of growth or may have problems with growth, so sometimes the measurement age doesn't match the "expected" gestational age. The best "age" is determined by an early ultrasound between 6 and 12 weeks gestation. Accuracy of ultrasound decreases as pregnancy progresses. ...Read more
I was told a baby's heartbeat doesn't beat until 5 weeks, is that 5 weeks gestation or fetal age? And how likely is it to see heartbeat at 5w 4d?
Very likely to see: At 5 weeks 4 days you will see a heartbeat. Before that it is a question of when can you see the heart beating and that has a lot of variables. Usually before 5 weeks it is not common to see but not impossible. ...Read more
Should your fundal height measure to gestational age or fetal age? I.E. If 25 weeks from LMP should it be 25cm?
How could warfarin effect an embryo that is 2 weeks old in fetal age (4 weeks gestational)? There isn't even a placenta yet
Great question: This assumes that you know exactly when you conceived. We see women all the time who have incorrect dates based on irregular timing of ovulation, conception and implantation. The fact is, warfarin is 'teratogenic' in the first trimester. Why would you take this risk? Talk to an mfm specialist. ...Read more
Fetal age due to LMP should be 7.2 but ultrasound after spotting showed the gestational age of 6.5 with flicker. Normal or can be some growth issue.?
Maybe?: Most women unless they are extraordinarily regular are not good at identifying their LMP. Also, of all the tests in medicine, ultrasounds are the most operator-dependent. Have the most experienced person in your area perform the test and interpret for you. Best Wishes! ...Read more
My gestational age is 6weak and fetal age is 4 weak but no foetal pole or heart beat seen in ultrasound. Only smal gestational sac is seen. Pls guide.
Early pregnancy.: During the early stages of pregnancy, the fetal age calculated by your LMP and the fetal age by the ultrasound can differ. This is frequent and can be a normal occurrence. Depending on the size in millimeters of the gestational sac, one might not see a fetal pole in a very early pregnancy. Seek the advice of your OB and they will follow your hormone levels and re-ultrasound you if necessary. ...Read more
BPD: Well we use more than just bpd to calculate the gestational age. Head circ., femur length, and abdominal circ. Also go into the calculation. However, 4.1cm bpd is consistent with about 17 weeks 4 days. ...Read more
Correct: Gestational age is always 2 weeks longer than fetal age because it accounts for the 2 weeks needed for you to ovulate. ...Read more
If its said that a 12 week old fetus measures 57 mm, than what is the gestational age of a fetus measuring 62mm?
Crown-rump length in fetus:
57 mm= 12+2 (50%) weeks,
62mm= 12+4 (50%) weeks
reference: http://www. Bmus. Org/policies-guides/23-17-3-161_ultbmus. Pdf. ...Read more
When a fetus is "measuring small" how is that determined? Wouldn't it just mean that the fetal / gestational age is off?
Yes and no: Yes, if the gestational dates are off. No, if they are not and the biparietal diameter of the fetus does not "measure up" to the appropriate age indicating "small for gestational age or intrauterine growth retardation.". ...Read more
What's the most accurate, the CRL or the FL, AC, HC? Which one gives you the most accurate fetal age? What are the errors?
All of the above.: I am not an Obstetrician, but as I understand it, no one measurement is "most accurate" for fetal age. That is why all are measured together - some sort of average of all the measurements is the best indicator of gestational age. Every baby is different, & due to genetics some babies will have larger heads for a given age, others will have long legs. So doctors follow growth of all parts over time ...Read more
Why are the number of days noted and important in determining fetal age? How are the number of days determined? (e.G. 11weeks + 4 days).
LMP: Fetal age is determined by your last menstrual period (lmp). So day 1 is actually the first day of your lmp, not the day you conceived as many think. So the 40 week due date is actually forty weeks from your last period. Woman with regular periods, this is fairly accurate. If you don't know the date of LMP or if your cycle is very irregular, these dates may be off, & your due date may be adjusted. ...Read more
Why are fetal measurements measured by weeks plus days and not just by weeks? Are the # of days just as important to determine gestational age?
Precision: By convention gestational age is stated in weeks. For precision and accuracy weeks and days are usually indicated when specifying a gestational age. For example, some tests may be done at 15 weeks but not at 14 weeks and 6 days - so the number of days is important as well. ...Read more
Is the gestational age of a fetus measured by how big it is? If so, can't some fetuses be bigger than others which can cause due dates to be off?
No.: That is close to an 11 week fetus. Far too large for an 8-9 week gestation. ...Read more
Need advice on what is the the difference between the gestational age of a fetus and how many weeks you are?
Same thing: The way you count is from your last period, it is 40 weeks from your last period until your due date so when you are 6 weeks gestational age it means 6 weeks from your last period which is how many weeks u are (most people get pregnant 2 weeks after their last period) but u always count from the 1st day of the last period, and in my office in coral springs, fl, I always do an early ultraosund. ...Read more
Gestational age: Ultrasounds factor in the manner in which we 'date' pregnancies and they are basing analysis of your baby's growth against all babies of the same age. Hope that helps! ...Read more
Yes. "Accurate".: Ultrasound pregnancy dating scans measure fetal size or age (time since conception), and convert the measurements to human gestational age. Gestational age is calculated by adding 2 weeks to the age of the fetus (to the time since conception), and roughly represents the total weeks since the first day of the last menstrual period (LMP). All dates are ESTIMATES, so 7w 5d means about 7w to 8w 3d. ...Read more
Can 12 week dating scan be off by 2 weeks? Could a 10 week gestational age fetus measure as big as 5.6cm?
Dr told me on 4/24 that my baby was measuring 7w/5d fetal age fr the u/s and gave me a DD of 12/7. Shouldn't my due date be 30w/1d fr 4/24?
Pls can someone explain to me why 2 weeks are subtracted from the ga to provide the fetal age, instead of for example 3 weeks, or 1 week? Thank you
Understand history: Sonograms have only been around for a blink of eye compared to the time humans have been having babies. A last menstrual period for much of human history was the only demonstrable data point that could be used to calculate due dates and gestational age. Following that tradition gestational age is dated from the theoretical last period 2 wks before ovulation and conception. ...Read more
Would there be a (big) difference in the measurement if a 12wk old fetus compared to a 9wk old fetus? The gestational age would be determined in u/s?
Yes: An first trimester sonogram is fairly accurate at dating a pregnancy (within a margin of error of about a week). At 12 weeks menstrual age with a viable pregnancy a sonogram measurement of 9 weeks would change the dating of the pregnancy and your due date should be based on that sonogram. Later sonograms should not change this established date. ...Read more