Fundal height dating
U/s has a 10-15% error of calculating baby weight throughout pregnancy and assigning dates varies with gestational age. Read more Ultrasounds and fundal heights can only "guess" at weights and gestational age unless done serially. It is notoriously inaccurate and depends on maternal weight for height, fibroids, amniotic fluid volume, lordosis of the maternal spine and experience of the examining prenatal care provider.
once the baby drops into the pelvis generally at 36 weeks gestation the fundal heights are "iffy". I would not read too much into it and rather rely on the ultrasound measurements at any time.
Most caregivers will record their patient's fundal height on every prenatal visit.
Measuring the fundal height can be an indicator of proper fetal growth and amniotic fluid development. Read more See 1 more doctor answer Ultrasound is more accurate compared to measurement of the fundal height.
The first trimester ultrasound will be more accurate in dating the pregnancy than the second trimester ultrasound in most cases. Read more Every baby grows at slightly different rates.
BACK TO TOP OF PAGE Estimated Gestational Age and Fetal Weight Calculator The calculator below uses Hadlock equations to estimate the gestational age [11,12, 46 ] and the Shepard and Hadlock equations to estimate the fetal weight 12-15]. al., Estimating fetal age: computer-assisted analysis of multiple fetal growth parameters.
After 20 weeks this distance in centimeters roughly equals your gestational age. In general the number of centimeters is about the number of weeks once beyond about 15 weeks. Read more See 1 more doctor answer The fundal height should not vary more than two centimeters from what your gestational age is at the time.
Your doctor would probably order an ultrasound to assess the situation further it you are lagging behind or measuring ahead. Read more Ob they know you and exactly what the scan showed, and your OB should ahve discussed the scan with you already !
It is recommended that crown-rump length be used up to 84 mm, and other parameters be used for measurements 84 mm the biparietal diameter (BPD) or head circumference (HC) is the best predictor of gestational age  .
However, using multiple parameters is superior to using a single parameter to establish a gestational age in the second trimester .