In addition to the ultrasound, the doctor has other methods of estimating gestational age.
A positive fetal heartbeat at this stage indicates a 95 percent chance that the pregnancy will proceed normally, according to Dr. Early transvaginal ultrasound, the most reliable way to determine a pregnancy due date, can date a pregnancy within a few days and is more accurate than determining a due date by the date of the last menstrual period.An accurate gestational age gives your prenatal care provider a basis for measuring the baby's development and growth.Before the advent of routine ultrasound in pregnancy, medical personnel estimated a baby’s due date by the date of the last menstrual period and by feeling the uterus and determining the size to see if it matched the given due date.With transvaginal ultrasound, checking for embryonic development known to occur within a certain time frame more accurately dates a pregnancy.Ultrasounds commonly are used to determine the age of a fetus.
The ultrasound machine and software allows the technician to see the baby's development and measure the baby.
Transvaginal ultrasound can see embryonic development about a week before transabdominal ultrasound, the American Pregnancy Association (APA) states.
A transducer, a wand-shaped probe, is inserted into the vagina and pressed against the vaginal walls directly next to the uterus.
Called the fundal height, the measurement used goes from the top of the uterus to the pubic bone.
This measurement in centimeters usually corresponds to the point in the pregnancy, so a woman at 24 weeks pregnancy should measure around 24 cm.
The timing of the ultrasound affects the accuracy of determining the gestational age. Later in the pregnancy, babies grow at much different rates, and babies at the same gestational age are more likely to vary in the measurements taken in the ultrasound.