Dating of the intrauterine fetal demise
For more details go to the following link: The Fetal Medicine Foundation.
Initially twins may be identified as 2 separate gestational sacs (ie diamniotic, dichorionic) They may be 2 fetal poles within the same gestational sac (monochorionic).
Measure the crown rump length (CRL) to estimate gestational age.
The rhombencephalon of the developing brain is visible as a prominent fluid space posteriorly.
Sometimes there is difficulty distinguishing between the maternal pulse and fetal heart beat.
Often technicians will take the mothers pulse at the same time to check if it is the fetus or the mothers .
These differences rarely effect gestational age dating by more than a day or two.
The very early embryonic heart will be a subtle flicker.
Failure to identify fetal cardiac activity in a fetus whose overall length is greater than 4 mm is an ominous sign.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.Using a transvaginal approach the fetal heart beat can be seen flickering before the fetal pole is even identified. It may be below 100 beats per minute but this will increase to between 120- 180 beats per minute by 7 weeks.A mass of fetal cells, separate from the yolk sac, first becomes apparent on transvaginal ultrasound just after the 6th week of gestation. 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.
The CRL is a reproducible and accurate method for measuring and dating a fetus.