Low birth weight (LBW) is defined by WHO as the weight of live born infants less than 2,500 g irrespective of their gestation. LBW is closely associated with fetal and perinatal mortality and morbidity. At the population level, the proportion of babies with a LBW is an indicator of a multifaceted public-health problem that includes long-term maternal malnutrition, ill health, hard work and poor health care in pregnancy. At an individual level, LBW is an important predictor of newborn health and survival and is associated with higher risk of infant and childhood mortality.1

Many socio-biological factors have been postulated to determine the birth weight of the newborn. The principal among these are maternal age, weight, height, education, parity, antenatal care, maternal smoking, and sex of the baby.2

In addition, LBW has a higher association with the incidence of infection, malnutrition and handicapping conditions during childhood.3,4

In developing countries, many women are short and underweight and the number of low birth weight (LBW) babies is particularly high (more than 30% in South Asia, 10-20% in other regions.5 LBW infants have less chance of survival; when they do survive, they are more prone to disease, growth retardation and impaired mental development. A good start in life is important and maternal nutritional status during pregnancy has repeatedly been demonstrated to be associated with pregnancy outcomes for the infant.6   Keeping all these in views, an attempt has been made to carry out a study on LBW babies at our institution.

Aim: This study aims at evaluating the risk factors for LBW in infants.

This was a prospective study conducted in the Department of Pediatrics, Tertiary Care Teaching Hospital over a period of 1 year. There was a total of 450 babies in this study, of which 150 were low birth weight babies and the rest 300 babies were weighing 2.5 kg or more. 

Babies were included in this study according to the following criteria:

Inclusion criteria

Live birth babies

Singleton babies

Exclusion criteria

Still births

Twin gestation

Babies with major congenital anomalies

Method of study

In this study, an analysis 150 mothers of LBW babies were done and compared with 300 normal weight babies. The variables were subjected to computer analysis using focus format. The data was analyzed using a Chi-Square for quantitative data. Chi square  test was used to calculate p value. P value was considered significant if <0.05. SPSS version 16 software is used to do the necessary statistical calculations.

The first weight of the new born was obtained after birth. The weight was measured preferably within the first hour of life before significant postnatal loss of weight has occurred.

Birth weight measurements were compared to measurements within 24 hours of birth. Heavy objects like metal forceps, for occluding umbilical cord were omitted. Weight scales were checked at intervals for accuracy.

The details of mothers who had delivered infants within the last 24 hours below 2500 grams were taken from the labour room and postnatal ward. The neonates were weighed naked within 24 hours after birth in a spring-dial baby weighing machine with sensitivity of 20 gms and graded upto 4 1/2 kgs in 20 gram units. Sex of the baby was noted. Any congenital malformation was ruled out.

SAMPLING MOTHERS

The same procedure used above for locating the infants was also used to trace the mother

1. Age of the mother was taken as recorded in the case sheet and also by questioning the mothers when data entered in the case sheet was not available.
2. Parity of the mother was noted down after questioning the mother as also the time interval between the previous delivery and birth of the child under study.
3. Weight of the mother was assessed within 24 hours after delivery. A spring balance which has a sensitivity of 50 gms was used for the purpose, after standardization and after allowing an inter and intrapersonal error of 50 gms

The mothers were weighed barefoot after checking the weighing scale for accuracy. If the mothers had any difficulty in walking, the weighing machine was taken next to their beds.

The advantage of spring balance was its easy transportability.

4. The height of the mother was usually measured within 24 hours after delivery along with other measurements where this was feasible. It was deferred till the mothers were able to stand erect.
5. Her standard of literacy was grouped into five categories: Illiterate, primary school, middle school, high school, college education.
6. The total family income and per capita income was assessed by questioning her in detail about the nature of the employment of the earning member in her family, number of earning members, family size and style of living.
7. Religion of the mother was determined by questioning her, whether she was born into that religion [or got subsequently converted was also enquired into] 8. Maternal diseases during antenatal period was enquired into.

The patients were clinically examined and the basic laboratory investigations were done to determine the following diseases:

A]           Tuberculosis -       

• Pulmonary
• Extra pulmonary

B]           Heart diseases-      

• Hypertension - blood pressure of 140/90 mm of hg or more on three consequent days (excluding PIH )
• Chronic rheumatic valvular disease,
• Congenital heart disease,
• Coronary disease

C]           Anemia- All the mothers who were anemic on clinical examination were evaluated for their hemoglobin status. A hemoglobin percentage of less than 9gms was considered significant.

Toxemias

• Pre-eclampsia manifesting with at 2 of the following:

-blood pressure of more than 140/90 mm of Hg

                              -albuminuria

                              -edema                                            

• Eclampsia: Convulsions or coma associated with signs of preeclampsia

E]           Antepartum hemorrhage: Bleeding from the placental site after the  28th week of pregnancy or during the first and second stage of labour.

-Accidental hemorrhage- Bleeding due to premature separation of a normally situated placenta. -Inevitable hemorrhage- Due to separation of the placenta, wholly or partially situated in the lower uterine segment [placenta previa]

F]           Diabetes mellitus  

• Evidence of glycosuria
• Fasting blood sugar of more than 140 mg% in cases of glycosuria

G] renal diseases- Nephritis and Nephrosis Urinary tract infections

9) Irrespective whether the cases are booked or unbooked, the following factors are taken into consideration:

Table 1: Incidence Of Low-Birth-Weight Babies Among Mothers Of Different Age Groups

X2 = 4.26, P=0.118, NS

Maternal age is divided into 3 groups: <20 years, 20-29 years and >30 years. Maternal age does not have any statistical significance in our study as p = 0.11

Table 2: Incidence Of Low-Birth-Weight Babies Among Mothers of Different Communities

x2 = 3.815, p=0.148, NS

Community is divided into 3 groups:

Hindus, Muslims and Christians. In our study, community does not have a significant association in our study as p = 0.148

Table 3: Incidence Of Low-Birth-Weight Babies Among Mothers of Different Levels of Education

x2 = 31.33, p<0.001, HS

Maternal education ranged from to graduation and was divided into 3groups- illiteracy, primary education and secondary education.  Association of maternal education and birth weight is statistically significant. Among the mothers who were having low birth weight babies, 50.7 % had no education; when compared to mothers who gave birth to normal babies (only 24.3% had no education in control group).  Thus, p value is highly significant.  

Table 4: Incidence Of Low-Birth-Weight Babies Among Mothers of Varried Socio-Economic Classes

x2 = 93.17, p<0.001, HS

Socioeconomic class is divided into 5 classes according to Kuppuswamy classification: I, II, III, IV, V. 54.7% of mothers who had LBW baby belonged to class III. There is a higher statistical significance between birth weight and socioeconomic class.

Table 5: Incidence Of Low-Birth-Weight Babies Among Mothers Undergoing Normal Vaginal Delivery Vs C Section

x2 = 12.19, p<0.001, HS

Deliveries were divided into 2 groups: esarean section (elective and emergency) and normal vaginal delivery (episiotomy and forceps delivery). Among the mothers who delivered LBW baby, 59.3 % were delivered by normal vaginal delivery.   p value is found to be significant. 

Table 6: Incidence Of Low-Birth-Weight Babies Among Mothers with Different Weights

x2 = 103.51, p<0.001, HS

There is a higher statistical signifance when the maternal weight is compared to birth weight ( p<0.001). In the mothers having weight < 50 kg, low birth weight incidence is 59.3%, while the incidence in those weighing > 50 kg is 40.6%.

Table 7: Incidence Of Low-Birth-Weight Babies Among Mothers with Different Heights

x2 = 132.46, p<0.001, HS

Maternal height is divided into 3 groups: <145 cm, 145-154 cm and 155-164cm. Among the mothers who delivered low birth weight babies, 91.4 % had short stature (height < 145cm). p value <0.001, thus the association of maternal height and birth weight is of statistical significance. 

Table 8: Incidence Of Low-Birth-Weight Babies Among Mothers Primi Vs Multi & Grand Multi

x2 = 9.28, p=0.010, sig

Parity ranged from 1 to 5 and is divided into 3 groups: Primi, Multi and Grand multi (G4 or more). In our study, parity has statistically significant association with regards to birth weight of baby. In our study, 42% of the mothers who delivered babies with birth weight < 2500 gms are multiparous when compared with control group. P value<0.010 and thus of statistical significance.     

Table 9: Incidence Of Low-Birth-Weight Babies Among Mothers with Varied Maternal Risk Factors

Fishers exact test p<0.001, HS        

There is a significant association between maternal risk factors like Oligohydramnious, PIH (pregnancy induced hypertension), and birth weight. Among the mothers who have delivered LBW babies, about 25% had oligohydramnious, 14% had PIH (Pregnancy induced hypertension). p value is significant especially with the group having oligohydramnious. The incidence of GDM (Gestational Diabetes Mellitus) and UTI (Urinary tract infections) are comparatively on the higher side in the study group.

Table 10: Incidence Of Low-Birth-Weight Babies in Relation to Sex of   Baby

x2 = 2.17, p=0.141, NS

About 50% of the low-birth-weight babies born were male. p = 0.141, thus there is no significant association between sex of baby and birth weight.

Table 11: Incidence Of Low-Birth-Weight Babies in Relation to Maternal Nutritional Status

x2 = 103.79, p<0.001, HS

In our study, mothers who had inadequate diet had higher incidence of LBW babies (72%) when compared with to controls. Thus there is a strong statistical significance in the association of maternal malnutrition with low birth weight.

Mothers are divided into 3 groups: <20 years, 20-29 years and >30 years. Maternal age does not have any statistical significance in our study as p = 0.118. This is similar to the study done by K.S. Negi7, but contrary to the earlier studies done by Parlington8 and Tabcharoen9, where maternal age <20 yearshas higher incidence of low birth weight. Among the mothers who delivered babies with birth weight > 2500 gms, majority (90%) belonged to the age group of 2029 years, which is similar to the findings observed by N.S. Nair et al. 10 Community is divided into 3 groups:  Hindus, Muslims and Christians. In our study, community does not have a significant association in our study as p = 0.148. This is similar to the study done by N.S. Nair et al10

Maternal education ranged from illiteracy to graduation and was divided into 3 groups- illiteracy, primary education and secondary education.  Association of maternal education and birth weight is statistically significant. Among the mothers who were having low birth weight babies, 50.7 %had no education.  p value is highly significant. This is similar to the study done by Selina Khatun11 and Saroj Parchiary12.

Maternal occupation is divided into 3 groups: housewife, labour and others. About 12.7% of mothers who had LBW babies were labourers when compared to the mothers of babies with normal birth weight (control group) where it is 0.7%. Thus, there is association of occupation and birth weight with p value highly significant in the labour group.

This is similar to the results of Selina Khatun11 and Saroj Parchiary12.

Socioeconomic class is divided into 5 classes according to Kuppuswamy classification: I (upper), II(upper middle), III(lower middle), IV(lower middle), V(lower). 54.7% of mothers who had LBW baby belonged to class III. There is a higher statistical significance between birth weight and socioeconomic class. This is similar to the studies done by N.S Nair4, James Donnelly13, Saroj Parchiary12 and Shanti Ghosh14.

Deliveries were divided into 2 groups: cesarean section (elective and emergency) and normal vaginal delivery (episiotomy and forceps delivery). Among the mothers who delivered LBW baby, 59.3 % were delivered by normal vaginal delivery.p value is found to be significant.

There is a higher statistical signifance when the maternal weight is compared to birth weight ( p<0.001). In the mothers having weight < 50 kg,  low birth weight incidence is 59.3%, while the incidence in those weighing > 50 kg is 40.6%. This is similar to the studies done by E J Love15, James Donnelly13, Niyogi16 and Shanti Ghosh14.

Maternal height is divided into 3 groups: <145 cm, 145-154 cm and 155-164 cms. Among the mothers who delivered low birth weight babies, 91.4 % had short stature (height < 145cm). p value <0.001, thus the association of maternal height and birth weight is of higher statistical significance. This is similar to the studies done by S. Ganesh kumar17.

Parity ranged from 1 to 5 and is divided into 3 groups: Primi, Multi and Grand multi (G4 or more). In our study, parity has statistically significant association with regards to birth weight of baby. In our study, parity has statistically significant association with regards to birth weight of baby. In our study, 42% of the mothers who delivered babies with birth weight < 2500 gms are multiparous when compared with control group. P value<0.010 and thus of statistical significance. This is similar to the studies done by S. Mukherji18, Mohsin19  , Datta Banik20 and Khin Nyunt21 according to whom birth weight increases with parity. Studies done by Khetua22 and Bachani23 also showed similar results.

There is a significant association between maternal risk factors like Oligohydramnious, PIH (pregnancy induced hypertension), and birth weight. Among the mothers who have delivered LBW babies, about 25% had oligohydramnious, 14% had PIH. p value is significant especially with the group having oligohydramnious. The incidence of APH (antepartum hemorrhage) and PROM (premature rupture of membranes) is comparatively on the higher side among the controls. Studies done by AMMark Anez Conteras 24 and LR Rahman 25 also showed that PIH is a risk factor for LBW.

About 50% of the low-birth-weight babies born were male. p = 0.141, thus there is no significant association between sex of baby and birth weight.  Similar results were obtained from the studies done by B Mondal 26.

In our study, mothers who had inadequate diet had higher incidence of LBW babies (72%) when compared with to controls. Thus there is a strong statistical significance in the association of maternal malnutrition with low birth weight. Similar results were obtained by A Dharmalingam.27

Maternal Hb% ranged from 6.5% to 13.5% and is classified into 3 groups: 10gm%,1011gm%,>11gm%. In our study, 32.7% of the mothers who delivered babies with birth weight < 2500 gms had Hb% < 10 gm%, thus p value is significant in the group having Hb% < 10 gm%.  SPachauri , S MMarevah 28, Khetua22 and Shanti Ghosh14 also mentioned that anaemia is a risk factor for LBW.

This study was conducted to know the maternal and bio-social factors that influence low birth weight babies. There was no significant association with maternal age and religion (community) with birth weight in our study. There was higher incidence of low-birth-weight babies among illiterate mothers. Mothers belonging to lower socioeconomic status had higher chance of delivering low birth weight babies. Parity has a significant relationship with birth weight with higher birth weight among women with higher parity. There is significant association of PIH and oligohydramnious with birth weight. There is no significant association of LBW with sex of the baby. Maternal malnutrition and anaemia have a significant association with LBW with higher incidence of Low birth weight among malnourished and anaemic mothers.

1. C Stevens-Simon; M Orleans Low-birthweight prevention programs: The enigma of failure. Birth. 1999 Sep;26(3):184-91
2. K Makhija et Al Sociobiological determinants of birth weights- Indian Journal of Pediatrics
3. 1989:56:639-643
4. G S Berkowitz; E Papiermik: Epidemiology of premature birth. Epidemiology reviews
5. 1993, 15: 414-443
6. D Dunin – Waswicz; Rowecka-Trazebickak Risk factors for cerebral palsy in very-    low birth weight infants. Journal of child neurology 2000, 15;417-420
7. A Dharmalingam Nutritional status of mothers and low birth weight in India. Maternal and child health Journal - 01-MAR-2010; 14(2): 290-8
8. Kramer M.S. (1987). Determinants of Low Birth Weight Methodological Assessment and Meta-Analysis. Bulletin of the World Health Organization, 65 (5), 663-737.
9. S. Negi;S.D. Kandapal; M. Kukreti epidemiological factors affecting low birth weight; vol. 8 No.1, January-March 2006
10. S N Parlington Second births to teenage mothers: risk factors for low birth weight and preterm birth. - Perspect Sex Reprod Health - 01-JUN 2009; 41(2): 101-9
11. C Tabcharoen Pregnancy outcome after age 40 and risk of low birth weight
12. Journal of Obstetrics and Gynaecology - 01-JUL-2009; 29(5): 378-83
13. N S Nair; V Nair; M Thankam - A study of birth weights of term infants at Calicut.
14. Journal of Obstetrics and Gynaecology of India 1963, 13:488
15. Selina Khatun and Mahmudur Rahman, socio-economic determinants of low birth weight in Bangladesh, Bangladesh Med Res Counc Bull  2008;34:81-86
16. . S Pachauri ; S M Marwah - A multifactorial approach to the study of the  factors influencing the birth weight in urban community of Delhi-Indian Journal of Medical Research 1971, 59, 1318
17. J Donelly Maternal,Fetal and Enviromental factors in prematurity-    American Journal of
18. Pediatrics and Gynaecology 1964, 88:918
19. S Ghosh ; V Attooja ; S K Mittal ; R K Verma Biosocial determinate of   birth weight.
20. Indian Pediatrics. 1977, 14:107
21. E J Love ; H Kinch,  Factors influencing the birth weight in normal pregnancy. American Journal of Obstetrics and Gynaecology 1965, 91: 342-349.
22. A K Niyogi ; B W Gajwani The influence of maternal factors on the  weight of newborn.
23. Journal of Indian Medical Association 1963. 40:64
24. Ganesh Kumar;H.N. Harsha Kumar;S. Jayaram and M.S. Kotian, Determinants of low birth weight : A case control study in a district      hospital in Karnataka, Indian Journal of Pediatrics 2010; 77 (1);87-89
25. S Mukherjee, ; S Biswas Birth Weight and its relationship to gestation period, sex,
26. Maternal age, Parity and Socio economic status. Indian Journal of Pediatrics 1970, 37:460 19. M Mohsin Maternal and neonatal factors influencing premature birth and low birth        weight in Australia. J Biosoc Sci - 01-APR-2003; 35(2) 161-7428.
27. N D Dattabanik– A study of different birth weight babies and related Indian
28. Pediatrics 1978, 16:327
29. Khin Nyunth; Mary Karen – Assessment of fetal growth from Birth Data at Central Women’s Hospital, Burma Medical Journal.  1981, 27 (4) 36.
30. S P Khetua; B K Manarha ; S Chatterjee and P K Roy Polodhi - Indian Pediatrics 1970,7:65
31. D Bachani ; D K Agarwal ; S Sharma and H N Mathew– Obstet Gynaec. Ind. 1985,35:52 24. A M MartÃnez Contreras Preeclampsia: Main maternal risk factor for low weight in preterm newborn - Ginecol Obstet Mex - 01-JUL- 2008; 76(7): 398-403
32. L A Rahman Association between pregnancy induced hypertension and low birthweight; a population based case-control study.– Asia Pacific Journal of  Public Health - 01-JAN-2008; 20(2): 152-8
33. Mondal- Risk factor for low birth weight in Nepali infants. Indian Journal of Pediatrics, 2000;67(7)
34. A Dharmalingam Nutritional status of mothers and low birth weight in India. - Maternal and child health Journal - 01-MAR-2010;     14(2): 290-8
35. S Pachauri ; S M Marwah - A multifactorial approach to the study of the    factors influencing the birth weight in urban community of Delhi-        Indian Journal of Medical Research 1971, 59, 1318.