Ultrasonographic Assessment of Third Trimester Fetal Kidney Length as a Measure of Gestational age in Growth Restricted Fetuses

Background: Obstetric ultrasound is the first imaging modality used to assess the foetus and track its development. When the last menstrual period (LMP) is unknown, foetal ultrasonography can help with dates. According to studies, over 30% of pregnant women forget their LMP date. When the gestational age (GA) is uncertain, the pregnancy's outcome may be undesirable. To assess the ultrasonographic fetal kidney length as a measure of gestational age in third trimester.

Methods: All participant women were in the third trimester whose gestational age was calculated by reliable LMP which was confirmed by recorded ultrasonic measurement of BPD, AC& FL).

Participant women were divided into 2 equal groups:

Group 1: normal pregnancy & average.

Group 2: patients with growth restriction fetuses.

Results: The mean length and width of the left kidney were similar in both groups, as the mean length of the left kidney in the IUGR group was (38.40 ± 4.000) while it was in the control group (38.17 ± 3.637). The average width of the left kidney in the intrauterine growth restriction group was (23.09 ± 2.339) while it was in the control group (23.16 ± 2.341), there were significant positive correlations between the different study variables. A positive association was found between gestational age, fetal weight, bipolar diameter, femur length and abdominal circumference with the length of the right kidney, and they also found a positive association with the length of the left kidney.

Conclusions: In absence of renal anomalies/ abnormalities, kidney measurements; length, weight, volume can be used to determine gestational age accurately.

No difference between measuring Rt or Lt kidney on determining GA. Also, no difference between measurements in female or male fetuses.

Kidney measurement is not affected in cases of IUGR and can be used as a reliable indicator for actual gestational age of the fetus in these cases.