Association between fetal weight and amniotic fluid index in women of Central India

The placenta is important for fetal growth and well-being. Defective placentation and impaired placental circulation may result in anomalies in fetal growth. Placental volume in the second trimester appears to be closely related to the neonatal weight. The association of body weight with urine output has been observed in human neonates. Our goal is to assess the association of the amniotic fluid index (AFI) with the estimated fetal weight (EFW).

Thirteen hundred and ninety-three pregnant women were prospectively studied by means of an ultrasound over a 12-month period. The fetal weight (FW) was estimated using a combination of fetal parameters - bi-parietal diameter, fetal trunk cross-sectional area, and femur length. AFI was assessed using the four quadrant method. The level of statistical significance was set at P ≤ 0.05.

There was no statistically significant association between AFI and EFW (P > 0.05; r = 0.413). We also did not find a significant association between AFI and EFW for all subdivisions of gestation age, except in the 24 - 28 weeks and 29 - 32 weeks' groups.

The FW calculations and amniotic index show a variation in values in late pregnancy. There does not appear to be a linear association between the ultrasound estimate of FW and the amniotic index. The implication of this is that the fetal size need not be taken into cognizance when alterations in amniotic fluid values are noted.