Comparative study of fetal weight estimation by clinical methods and ultrasound and its correlation with the actual birth weight

Accurate estimation of fetal weight is of key importance in the Obstetrician’s  decision-making process in the antepartum and intrapartum management of pregnancy, along with gestational age and adequacy of maternal pelvis, to decide the management of labor and mode of delivery. Accurate estimates are essential, since abnormal fetal growth may be associated with perinatal and maternal risk.

Both low and excessive weights at delivery are associated with an increased risk of newborn complications during labour and puerperium.

Delivery of a macrosomic fetus is associated with prolonged labor and various delivery traumas, including shoulder dystocia, brachial plexus injuries and intrapartum asphyxia, as well as increased maternal risks such as birth canal injuries and postpartum hemorrhage.

World Health Organization (WHO) has recommended that newborns with birth weight less than 2500 grams may be considered to fall in low birth weight categories carrying relatively higher risk of perinatal and neonatal morbidity and mortality. About 80% of neonatal death and 50% of infant deaths occur among these group. These infants are more prone to develop recurrent infection, malnutrition, diabetes, hypertension and neuro developmental handicaps in their life time. Hence low birth weight is an important risk factor for adverse outcome in later life. Therefore estimation of fetal birth weight in intra uterine period happens to be of greater significance in early detection of intra uterine growth restriction and prevention of prematurity.

Management of diabetic pregnancy, vaginal birth after a previous caesarean section, and intrapartum management of foetuses presenting by the breech will be greatly influenced by estimated fetal weight.

Clinical methods of fetal weight estimation like Johnson’s formula and Insler’s formula can be used to predict expected fetal weight in low resource settings. Ultrasound is also used for estimation of expected fetal weight . But, it is not easily available in all places offering obstetric care, especially in low resource settings. Fetal weight estimation using ultrasound needs training, expertise and an expensive equipment. In such circumstances clinical methods of estimating fetal weight can aid in obstetric decision making.