The primary goal in modern obstetrics is to deliver a healthy baby to a healthy mother with minimal complications. Birth weight plays a pivotal role in determining neonatal outcomes and survival1. Accurate estimation of fetal weight is thus a critical component in the management of labor and delivery, influencing a range of obstetric decisions. The estimated fetal weight (EFW) is routinely incorporated into antenatal evaluations to anticipate and address potential perinatal complications. For example, in pregnancies complicated by diabetes, decisions about the mode of delivery2, including the feasibility of a vaginal birth after a cesarean section, are significantly influenced by the estimated fetal weight. Similarly, in high-risk situations such as intrauterine growth restriction (IUGR), suspected macrosomia, or previous cesarean sections, knowledge of fetal weight helps in planning and executing labor management strategies3, 4.Low birth weight infants — including those who are small for gestational age, growth-restricted, or preterm — are associated with increased perinatal morbidity and mortality due to their vulnerability to hypoglycemia, hypothermia, respiratory distress, and infections. Conversely, large babies, including those classified as large for gestational age or macrosomic, face a different set of challenges5, including shoulder dystocia, brachial plexus injuries, facial nerve palsies, and an increased risk of birth trauma. Additionally, these large babies may predispose the mother to complications such as perineal tears and postpartum hemorrhage. Therefore, accurate fetal weight estimation becomes crucial not only for neonatal safety but also for maternal well-being6.Fetal growth is determined by a complex interplay of environmental, maternal, fetal, and placental factors7. These include racial or ethnic background, maternal age, parity, socioeconomic conditions, nutritional status, maternal infections, and fetal genetic factors8. Abnormalities of fetal growth can be detected clinically or with the help of ultrasonography (USG). Clinical examination remains an important screening tool, especially in low-resource settings where advanced technology may not be readily available. Simple bedside methods, such as measurement of the symphysio-fundal height (SFH) and abdominal girth (AG), are commonly employed for fetal weight estimation in resource-constrained settings9,10. Clinical methods, though user-dependent, can be useful, rapid, and cost-effective, especially where ultrasound equipment is either not available or its use is limited by lack of trained personnel. Various clinical formulas have been developed over time to estimate fetal weight11. Among these, Johnson’s formula is a widely used method that relies on symphysio-fundal height measurements, while Dare’s formula utilizes the product of SFH and AG to estimate the expected fetal weight, offering a fairly acceptable predictive accuracy with a simple approach. Dare’s formula, in particular, uses the product of SFH in centimeters and abdominal girth at the umbilical level, expressing the result directly in grams, and has shown a reasonable correlation with actual birth weight12.On the other hand, ultrasound-based fetal weight estimation has evolved considerably, with the Hadlock formula being one of the most commonly employed methods. The Hadlock formula incorporates multiple biometric parameters including biparietal diameter, head circumference, abdominal circumference, and femur length, allowing a more sophisticated and comprehensive estimate of fetal weight. Despite its higher accuracy, ultrasound estimation requires expensive equipment, training, and operator expertise, which may not be universally available in all healthcare settings13,14. Therefore, while ultrasound methods are considered the gold standard in many tertiary centers, clinical estimation methods continue to have a significant role, particularly in peripheral or rural healthcare systems15.

AIM

To compare the fetal weight estimated by Johnson’s formula, Dare’s formula, and the Hadlock ultrasound formula in term pregnancies.

This prospective comparative observational study was conducted in the Department of Obstetrics and Gynaecology at …… over a period of …… The study population consisted of pregnant women with singleton term pregnancies (≥37 week’s gestation) who were admitted for delivery. Inclusion criteria included singleton pregnancy with cephalic presentation, term gestation between 37 and 42 weeks, the absence of gross fetal anomalies, and willingness to provide informed consent to participate. Women with polyhydramnios or oligohydramnios, multiple pregnancies, malpresentations, fetal anomalies, intrauterine fetal demise, or those in active labor with cervical dilatation greater than 5 cm were excluded from the study.

STUDY PROCEDURE

After informed consent, a thorough obstetric examination will be conducted.

Symphysio-fundal height (SFH) will be measured in centimeters from the upper border of the pubic symphysis to the uterine fundus.

Abdominal girth (AG) will be measured in centimeters at the level of the umbilicus.

Fetal weight will be estimated using:

Johnson’s formula: (SFH - x) × 155, where x = 13 if the fetal head is engaged, 12 if not engaged.

Dare’s formula: SFH × AG (grams)

Hadlock formula (ultrasound): based on BPD, HC, AC, FL measurements as per standard Hadlock charts.

Table 1: Maternal Characteristics:

Among the 200 mothers studied, 12.5% were aged ≤20 years, 30% were 21–25 years, 32.5% were 26–30 years, 13.5% were 31–35 years, and 11.5% were above 35 years.

Table 2: Parity:

Of the 200 mothers, 39% had parity 1, 27.5% had parity 2, 19.5% had parity 3, and 14% had parity 4.

Table 3: Gestational age:

Among the participants, 74% had a gestational age between 39 and 39+6 weeks, while 26% had a gestational age of 40 weeks or more.

Table 4: Neonatal Actual Birth Weight (n=200)

The mean actual birth weight was 3010 ± 420 g, with a range of 2200 to 3900 g.

Table 5: Estimated Fetal Weight by Various Formulas (n=200)

The mean estimated birth weight by the Johnson formula was 2890 ± 440 g (range 2100–3800 g), by the Dare formula was 2950 ± 410 g (range 2200–3850 g), and by the Hadlock formula was 3040 ± 400 g (range 2300–3950 g).

Table 6: Errors in Weight Estimation Compared to Actual Birth Weight (n=200)

The mean error for the Johnson formula was −120 ± 150 g (range −400 to +200 g), for the Dare formula was −60 ± 130 g (range −300 to +180 g), and for the Hadlock formula was +30 ± 110 g (range −200 to +250 g).

Birth weight is a crucial factor influencing fetal and neonatal morbidity, especially among preterm and small-for-date infants. Accurate knowledge of fetal weight allows obstetricians to plan appropriate management strategies, ultimately reducing perinatal morbidity and mortality. In the present study, clinical methods of fetal weight estimation were found to be comparable in accuracy to ultrasound estimation and actual birth weight. The symphysio-fundal height remains an important clinical measure for estimating fetal weight, as utilized in both Johnson’s and Dawn’s methods. Overall, combining clinical parameters with ultrasound can support safer obstetric care and improve outcomes for mothers and newborns.

In this study, the majority of mothers (32.5%) belonged to the 26–30 years age group, followed by 30% in the 21–25 years age group. A smaller proportion of mothers (13.5%) were aged 31–45 years. Mothers aged ≤20 years accounted for 12.5% of the study population. Additionally, 11.5% of mothers were older than 35 years. This distribution highlights that most pregnancies occurred among women in their mid to late twenties. a figure similar to Tritapant et al.’s16 investigation involving patients and Peregrine et al.’s17 research with participants explored cohorts of 266 and 262 patients, respectively. The average age of the patients was 25.58 ± 4.11 years, ranging from 18 to 37 years.

In this study, primiparous women (parity 1) constituted the largest group, accounting for 39% of participants. Women with parity 2 made up 27.5% of the study population. Those with parity 3 represented 19.5%. A smaller proportion of women, 14%, had a parity of 4. Overall, most mothers in the study had one or two previous deliveries.

In this study, the majority of mothers (74%) delivered between 39 and 39+6 weeks of gestation. A smaller proportion, 26%, delivered at 40 weeks or beyond. This indicates that most births occurred at term before reaching 40 weeks. Such distribution reflects a tendency toward delivery in the later part of term gestation.

The mean actual birth weight of newborns in this study is 3010 ± 420 grams. The minimum recorded birth weight is 2200 grams, while the maximum reaches 3900 grams. This indicates a considerable variation in birth weights among the study population. Most newborns fell within the normal birth weight range. These findings reflect generally favorable fetal growth patterns in our study.

In this study, the estimated birth weight by the Johnson formula show a mean of 2890 ± 440 g, with a range of 2100 to 3800 g. The Dare formula yield a slightly higher mean of 2950 ± 410 g, ranging from 2200 to 3850 g. The Hadlock formula estimate an even higher mean birth weight of 3040 ± 400 g, with a range of 2300 to 3950 g. These formulas demonstrate some variability in their estimations compared to actual birth weight. Overall, Hadlock formula estimates were closest to the true mean birth weight. This suggests Hadlock offers better accuracy in predicting fetal weight among the formulas assessed.

In this study, the mean error of the Johnson formula is –120 ± 150 g, ranging from –400 to +200 g. The Dare formula shows a smaller mean error of –60 ± 130 g, with a range between –300 and +180 g. The Hadlock formula demonstrates the least mean error of +30 ± 110 g, spanning from –200 to +250 g. In our study, the least average discrepancy in fetal weight estimation was observed with the Dare formula, while the highest discrepancy was associated with Johnson’s formula. This finding aligns with the broader literature by patil , where ultrasound-based methods, including the Hadlock formula, have demonstrated higher precision compared to clinical formulas. In comparison, the referenced study reported mean errors of 208.33 ± 153.08 g for ultrasonography, 211.64 ± 135.41 g for Dare’s, and 293.37 ± 159.37 g for Johnson’s formula, with statistically significant differences between them (*P* < 0.05). The lowest mean and median errors were consistently found with ultrasonography, highlighting its superior accuracy in estimating fetal weight, similar to the performance of the Hadlock formula in our cohort. These results confirm that Johnson’s formula tends to over- or underestimate fetal weight to a greater extent, while sonographic methods (USG or Hadlock) provide more consistent and reliable estimates. This pattern is consistent with previous studies by Afzal et al.,18 Rashid et al., Konwar et al.,19 and Paravathavarthini et al.20, which also supported the superior precision of ultrasound-based fetal weight estimation over purely clinical methods.

Accurate fetal weight estimation is vital for optimal perinatal care and reducing neonatal morbidity and mortality. In this study, the Hadlock formula showed the best agreement with actual birth weight, followed by Dare’s formula, while Johnson’s formula displayed the largest discrepancy. These findings support the higher precision of ultrasound-based methods over purely clinical estimations. Combining sonographic measurements with clinical assessments may further enhance fetal weight prediction. Most mothers in the study were in their twenties, and the majority delivered at term, with generally favorable birth weights observed. These results highlight the importance of integrating ultrasound for safer obstetric planning. Continued research in diverse populations will help refine these predictive tools further.

1. Jolly MC, Sebire NJ, Harris JP, Robinson S. Risk factors formacrosomia and its clinical consequences. Eur J Obstet GynaecolReprod Biol 2003 Nov;111(1):9-14.
2. Boyd ME, Usher RH, McLean FH. Fetal macrosomia:Prediction, risks and proposed management. Am J ObstetGynecol 1983 Jun;61(6):715-22.
3. Naumi G, Collodo Khoury F, Bombard A, Julliar K, Weiner Z.Clinical and sonographic estimation of fetal weight performed during labor by residents. Am J Obstet Gynecol 2005May;192(5):1407-09.
4. Hendrx NW, Grady CS, Chauhan SP. Clinical vs sonographicestimates of birth weight in term parturients. A randomised clinical trial. J Reprod Med 2000 May;45(5):390-94.
5. Nahum GG. Detecting and managing fetal macrosomia.Contemp Obs/Gyn 2000 June;45(6):89-119.
6. Bhandary Amritha A, Pinto Patric J, Shetty Ashwin P.Comparative study of various methods of fetal weight estimationat term pregnancy. J Obstet Gynecol Ind 2004 July-Aug;54(4):336-39.
7. Dawn CS, Modak GC, Ghosh A. A simple procedure fordetermination of antenatal fetal weight. J Obstet Gynecol Ind1983;33:1333-37.
8. Sherman DJ, Arifli S, Tovbin J, Siegel G, Caspi E, Bukovsky I. Acomparison of clinical and ultrasonic estimation of fetal weight.Obstet Gynaecol. 1998; 91:212-7.
9. Amritha BA, Patric PJ, Ashwin SP. Comparative study of variousmethods of fetal weight estimation at term pregnancy. J ObstetGynecol India. 2004; 54:336-9.
10. Ayoola OO, Orji EO, Adetioloya VA, Nzeh DA. Accuracy ofvarious ultrasound formula in predicting fetal weight in anigerianpopulation. J Chinese Clin Med. 2008: 1; 3:3-11.
11. ChauhanSP, Lutton PM, Bailey KJ, Guerrier JP, Morrison J.
12. Intrapartum, clinical, sonographic and parous patients estimatesof new born birth weight. Obstet Gynecol. 1992; 79(6):956-8.
13. NayakL et al. Comparitive study on Johnsons formula,Insler’sformula and Hadlock’s formula for estimating fetal weight atterm. J Evid Med Healthcare. 2017; 4:600-5.
14. Kayem G et al. Comparison of fundal height measurement andsonographically measured fetal abdominal circumference in theprediction of high and low birth weight at term. Ultrasound Obstet
15. 2009; 34:566-71.14. Tushar et al. Comparitive study of fetal weight estimation byvarious methods among term pregnancies. J Evol Med Dent Sci.2014; 3(41):10291-10296.
16. Yazdani SH, Bouzari Z, NazariAM. Comparison of fetal weightestimation with clinical, ultrasonographic methods, andcombined formula of ultrasonography and maternal weight.Iranian J Obstet Gynecol Fertility. 2014; 17(106):1-7.
17. Titapant V, Chawanpaiboon S, Mingmitpatanakul K. A comparison of clinical and ultrasound estimation of fetal weight. J Med Assoc Thai 2001;84:1251–7 Cited Here | PubMed | Google Scholar
18. Peregrine E, O’Brien P, Jauniaux E. Clinical and ultrasound estimation of birth weight prior to induction of labor at term. Ultrasound Obstet Gynecol 2007;29:304–9 Cited Here | View Full Text | PubMed | CrossRef | Google Scholar
19. Afzal M, Farooq MA, Said NF. Examine the accuracy of ultrasound in estimation of fetal weight and comparison with post delivery birth weight. Pak J Med Health Sci 2019;13:273–5Cited Here | Google Scholar
20. Rashid SQ. Accuracy of sonographic fetal weight estimation in Bangladesh. J Med Ultrasound 2015;23:82–5Cited Here | CrossRef | Google Scholar
21. Konwar R, Basumatary B, Dutta M, Mahanta P. Accuracy of fetal weight estimation by ultrasonographic evaluation in a northeastern region of India. Int J Biomater 2021;2021:909033810.1155/2021/9090338 Cited Here | Google Scholar