How to convert abdominal diameter to abdominal circumference

Many obstetricians and gynecologists can predict the fetus's date of birth based on the fetal abdominal neck and the pregnant woman's abdominal circumference when performing prenatal examinations. Many expectant mothers express confusion and do not know how the doctor calculates this. They want to measure and calculate it themselves at home and are very much looking forward to the arrival of their baby. So how are the full abdominal diameter and abdominal circumference converted? Let’s take a look together below.

The fetal abdominal diameter is used to determine the gestational age and estimate the maturity and size of the fetus.

The modern term for the part of the trunk of humans and vertebrates between the thorax and pelvis.

Begin measuring abdominal circumference from the 16th week of pregnancy. Stand up, with the navel as the reference, and circle the abdomen horizontally. The value measured is the abdominal circumference.

The average waist circumference increases by 0.8 cm per week. The fastest growth occurs during the 20th to 24th week of pregnancy; after the 34th week of pregnancy, the growth rate of abdominal circumference slows down. If the abdominal circumference measured at 16 weeks of pregnancy is taken as the base number, the average growth value is 21 cm by full term. When growth does not follow numerical values, it often causes worry and confusion for pregnant women. In fact, the growth of abdominal circumference is not exactly the same for each pregnant woman. This is because:

(1) Before pregnancy, everyone’s weight and waist circumference are different.

(2) The increase in abdominal circumference after pregnancy is not only due to the enlargement of the fetus and uterus, but also due to factors related to the pregnant woman herself.

(3) Some pregnant women experience pregnancy reactions and have difficulty eating, and their abdominal circumference does not increase significantly in the early stages. When the reaction disappears, appetite increases.

(4) Some pregnant women gain weight rapidly after pregnancy, and their subcutaneous fat in the abdomen thickens quickly. Not only does their waist circumference increase, but their abdominal circumference also increases faster than that of other people.

(5) Some pregnant women have obvious water and sodium retention, which will cause a significant increase in abdominal circumference.

Therefore, measuring the growth of the uterus and fetus solely by the growth of abdominal circumference is limited and one-sided, and should be combined with other examinations for comprehensive analysis.

The fetus has entered a phase of rapid growth, the uterus has begun to enlarge, and has left the pelvic cavity. The fundus of the uterus can be felt above the pubic symphysis. During the prenatal examination, your doctor will give you an accurate answer as to whether the position of the fundus of the uterus is consistent with the gestational age.

If your doctor says that the height of your uterine fundus does not match the predicted gestational age, but does not recommend further examination, such as B-ultrasound, you do not have to worry. The doctor will determine whether it is an abnormality or an individual difference.

By the end of the 16th week, the abdomen may bulge slightly, but the bulge will not be noticeable for thinner or taller pregnant women. If the pregnant women around you are in the same stage of pregnancy as you and their bellies are already bulging, you don't have to worry, because no two pregnant women's pregnancies are exactly the same.