What measurement to determine gestational/menstrual age can be performed? MSD CRL yolk sac diameter heart rate

To determine gestational/menstrual age, several measurements can be performed:

1. Mean Sac Diameter (MSD): This is an ultrasound measurement that is used in early pregnancy to determine the size of the gestational sac which contains the embryo. It is usually done between 5 to 6 weeks of gestational age.

2. Crown-Rump Length (CRL): This is the measurement of the length of the human embryo or fetus from the top of the head (crown) to the bottom of the buttocks (rump). It is typically used to estimate gestational age between 6 to 13 weeks.

3. Yolk Sac Diameter: The yolk sac is a membranous sac attached to the embryo, which provides early nourishment to the embryo before the placenta is fully formed. Its size can be used to estimate gestational age in early pregnancy, usually up to about 10 weeks.

4. Heart Rate: The fetal heart rate can also be used to estimate gestational age. The heart rate of a fetus is much faster than that of an adult. It starts at about 5 weeks and varies throughout pregnancy. However, it is less accurate than the other methods and is usually used in conjunction with them.