Maternal DeterminANTS of Giving Birth to
low-birth-weight Neonates

 

Shiva Rafati MD^•, Hajieh Borna MD, Mohammad-Bagher Akhavirad MD,

Nader Fallah MSc

 

Authors’ affiliation: Department of Pediatrics, Shahed University of Medical Sciences, Tehran, Iran.

•Corresponding author and reprints:  Shiva Rafati MD, Department of Pediatrics, Shahed University of Medical Sciences, Tehran, Iran.

Fax: +98-21-88963122, E-mail: ramin@excelicon.com.

 

Background: Low-birth-weight (LBW) is universally used as an indicator of health status and is an important subject of national concern and a focus of health policy. LBW has been shown to be associated with a higher risk for childhood mortality and morbidity.

Objective: To determine the important risk factors which could affect the delivery of LBW neonates.

Methods: This case-control study was undertaken to determine some risk factors for LBW in two university hospitals in Tehran during a 12-month period between 2002 and 2003. One hundred and sixty neonates constituted the LBW group and 300 neonates constituted the control group. Maternal risk factors including body mass index (BMI), educational level, interval between pregnancies, history of previous delivery of LBW neonates, abortion, infertility, unwanted pregnancy, and diseases were analyzed between the two groups. Mean of maternal age was similar between the two groups.

Results: Of 160 LBW neonates, 58% were females and 42% males. It was found that mother’s BMI, unwanted pregnancy, educational level of mother, short and long intervals between pregnan­cies, previous history of delivering LBW neonates, and maternal diseases are associated with an increased risk of LBW.

Conclusion: The majority of factors which lead to the delivery of LBW neonates are preventable.

 

Archives of Iranian Medicine, Volume 8, Number 4, 2005: 277 – 281.

 

Keywords: Low-birth-weight (LBW) · maternal risk factors

Introduction

 

ow-birth-weigh (LBW) is defined as a weight at birth of 2,500 g or less.^1,2 In 1997, World Health Organization (WHO) estimated that 17% of babies born world­wide are LBW, with marked differences between the incidence in developing (19%) and indust-rialized countries (7%).³

LBW babies are 17 times more likely than those weighing > 2,500 g, to die during the perinatal period, and 40 times more likely to die during the neonatal period which accounts for 71% of all the neonatal deaths.⁴

 It is generally assumed that prevention of LBW results in a corresponding reduction in perinatal mortality. The identification of factors contributing to LBW is therefore of paramount importance.⁵

Low socioeconomic status, maternal under­nutrition, anemia and illness, inadequate prenatal care, obstetric complications, and maternal histories of premature LBW infants have all been reported to influence the occurrence of LBW. These factors operate to various extents in different environments and cultures.⁴ Neonatal LBW rate in Iran was 5% in 1995 (WHO reported).³

The purpose of this study was to determine the important maternal risk factors associated with   the delivery of LBW neonates.

 

Patients and Methods

 

This investigation was a case-control study carried out at two university hospitals in Tehran from 2002 to 2003. All live neonates with a birth weight of ≤ 2,500 g, delivered in these two hospitals during one year, were included as cases. Two babies with birth weights of > 2,500 g who were born consecutively after each case, constituted the control group. Twenty neonates who showed complications were excluded from the study. Therefore, 300 neonates remained in the control group. Weighing of neonates was carried out after birth. Obstetric history was obtained by personal interview and from the antenatal records, and was recorded on a standardized and pretested questionnaire.

Maternal characteristics included age, height, weight, educational status, interval between birth of the newborn baby and the previous delivery, medical diseases, and an unwanted pregnancy. Baby characteristics included sex and the birth weight.

Information regarding the history of previous LBW deliveries, abortions, and infertilities was obtained during the interview. Maternal height was measured against a wall height scale to the nearest centimeter. Maternal weight was measured to the nearest kilogram and body mass index (BMI) was subsequently calculated. Babies were weighed to the nearest 10 g by trained midwives in the labor ward, using a balanced Seca scale, within 15 min after birth. The scale was always checked and zeroed before weighing.

All the data were entered into the SPSS package (version 10). Proportional differences between cases and controls were analyzed using the Chi-square or Fischer’s exact test, taking a level of significance of P < 0.05. In addition, the t-test was also used to comapre the maen of two quantitative variables. For computing the odds ratio (OR) and comprehensive analysis, logistic regres­sion models were applied.

 

Results

 

The mean birth weight in LBW group babies (n = 160) was 2,293 g and in the control group (n = 300) was 3,293 g. There were more females among the LBW neonates (58%). In the LBW group, 141 neonates had a weight of 2,000 – 2,500 g, 16 neonates weighing between 1,500 – 1,999 g, and three weighed between 1,000 – 1,449 g.

 

Maternal characteristics

Among the studied mothers, the most frequent age group was 20 – 35 years (Table 1). The mean±SD maternal age among the LBW group was 27.3 ± 5.0 years, and in normal group was 26.8 ± 5.3 years (P > 0.05).

 

 

 

Mothers were divided into three subgroups according to their BMI: favorable (20 – 25), acceptable (25 – 30), and unfavorable (< 20 or >30). In the LBW group, 18% of mothers had an unfavorable BMI. In the control group, on the other hand, only 8% of mothers had an unfavorable BMI (Table 1, P = 0.004).

 Mothers were divided into five subgroups according to their education: 1) illiterate, 2) primary school certificate, 3) guidance school certificate, 4) high school diploma, and 5) university degree. In the LBW group, 20% of mothers, and in the control group, 7% had elementary school education (Table 2, P < 0.05).

 

 

Intervals < 1 year or ≥ 10 years between pregnancies were also associated with  giving birth to LBW neonates (P < 0.05, Figure 1).

 

 

In the LBW group, 20 (13%) mothers had a history of previous delivery of LBW neonates in contrast to the mothers of control group, in whom 13 (4%) had a history of previous  delivery of LBW neonates (P < 0.001).

In the LBW group, 10 mothers had unwanted pregnancies in contrast to the mothers of normal group, in whom only three had unwanted pregnancies (P < 0.00001).

 Maternal diseases such as preeclampsia, hypertension, and urinary tract infection (UTI) are also related to the delivery of LBW neonates. A history of UTI was detected in 60% of mothers in the LBW group, in contrast to 28% in the control group (P < 0.00001). History of preeclampsia was observed in 16% of mothers in the LBW group, in contrast to 1.3% in the control group (P < 0.00001). History of hypertension was noted in 24% of mothers in the LBW group, in contrast to 8% in the control group (P < 0.00001).

There was no relationship between the history of abortion, infertility, consanguine marriage, maternal diabetes, and the delivery of LBW neonates.

In our study, the number of mothers drinking alcohol or smoking cigarettes was remarkably low.

 

Discussion

 

Our findings have proven the existance of some important risk factors regarding the delivery of LBW neonates. Since the maternal age has been the same in both groups (LBW and control), other risk factors which could affect the delivery of LBW neonates have been analyzed below.

One of the most important factors is mother’s BMI at the beginning of pregnancy (Table 1). The relationship between a low maternal prepregnancy BMI and adverse pregnancy outcomes has been known for several decades. Other evidence indicates that women with a low prepregnancy BMI are still more likely to give birth to smaller infants than heavier women, even when their gestational weight gains were similar.^{7, 8} Our finding was in keeping with previous studies. ⁹

The second risk factor for giving birth to a LBW neonate is the mother’s education (Table 2). As the education increases, the chance of delivering LBW neonates decreases. Among mothers’s with elementary education, 60% had LBW neonates. This is in contrast to the frequency (30%) observed among group of mothers with a university degree. Certainly, educated mothers have a better reproductive behavior. Our finding is in agreement with other studies.^{9, 10}

 

 

 The third risk factor is the interval between pregnancies. The results of this study support the findings of Zhu et al.¹¹ They found that infants conceived less than six or more than 120 months after a live birth had a respective OR of 1.4 and 2 for the LBW delivery.¹¹ This is in contrast to Fourn et al who found that a short interval between pregnancies had no significant correlation with LBW.¹²

Another important risk factor is unwanted pregnancy which increases the likelihood of delivery of a LBW neonate by 7 folds; a finding in keeping with Ko et al.¹³

Another risk factor is the history of previous   delivery of LBW neonates (OR = 4). This finding is in agreement with other reports.^{9, 14 – 16} Mansour  et al found that the history of giving birth to a LBW neonate increases the chance delivering LBW neonates by three times.⁹ It is probable that multiple etiologic factors that affect neonatal weight are generally the same in all pregnancies of the same mother.

There was also a significant relationship between maternal diseases such as preeclampsia, hypertension, premature rupture of membrane (PROM), UTI, and the delivery of LBW neonates .

There is a four-fold increase in delivering LBW neonates in preeclamptic mothers (OR = 4.59). This finding supports other studies, reporting preeclampsia to be associated with a 3.8-fold increase in the risk of delivering LBW neonates.^{14, 18 – 20}  

Hypertension also increases the risk of   delivering LBW neonates by 2.69 folds.^{14, 15, 19, 20}UTI during pregnancy also increases the risk of delivery of LBW by 4.09 folds.¹⁶ There was no relationship between maternal diabetes and the delivery of LBW neonates. On the contrary, diabetic mothers gave birth to heavier neonates.

Since LBW is one of the important risk factors determining the infant mortality and morbidity, and since the majority of factors which lead to the delivery of LBW neonates are preventable, it is hoped that with close cooperation of gynecologists and pediatricians along with training of mothers and young women, the number of such incidences would be minimized.

 

References

 

1         Behrman RE, Kliegman R, Jenson HB. Nelson Textbook of Pediatrics. 17th ed. Philadelphia, Pa: Saunders; 2004: 550.

2         Taeusch HW, Ballard RA. Avery’s Diseases of the Newborn.7th ed. Philadelphia: WB Saunders; 1998: 90.

3         WHO. Birth weight. J World Pediatr Health. 1995; 31 – 37.

4         Peters HR, Vince JD, Friesen H. Low- birth-weight at a Papua New Guinea highlands hospital. J Trop Pediatr. 2001; 47: 17 – 23.

5         Leong WP, Wiegas OA, Ratnam SS. Premature child birth-social and behavioral risk in Singapore. J Biosocial Science. 1993; 25: 465 – 472.

6         Shieve LA, Cogswell ME, Scanlon KS. Prepregnancy BMI and pregnancy weight gain: associations with preterm delivery. Obstet Gynecol. 2000; 96: 194 – 200.

7         Institute of Medicine. Committee on Nutritional Status during Pregnancy and Lactation. Nutrition during Pregnancy. Washington DC: National Academy Press; 1990: 81 – 82.

8         Osman NB, Challis K, Cotiro M, Nordahl G, Bergstrom S. Prenatal outcome in an obstetric cohort of Mozambican women. J Trop Pediatr. 2001; 47: 30 – 38.

9         Mansour E, Eissa AN, Nofal LM, Salam I. Incidence and factors leading to LBW in Egypt. Int Pediatr. 2002; 1: 223 – 230.

10      Cherly B, Limin S, Nighat Q, Kathleen KB. The epidemiology of LBW and preterm delivery in Hawai'i, 2000 – 2001. Californian J Health Promotion. 2003; 1: 83 – 90.

11      Zhu BP, Rolfs RT, Nangle BE, Horan JM. Effects of interval between pregnancies on perinatal outcomes. N Engl J Med. 1999; 340: 589 – 594.

12      Fourn L, Goulet L, Sequin L. Birth intervals and birth of LBW in Benin [in French]. Med Trop (Mars). 1996; 56: 163 – 166.

13      Ko YL, Wu YC, Chang PC. Physical and social predictors for preterm births and LBW infants in Taiwan. J Nurses. 2002; 10: 83 – 89.

14        Ramana R. LBW incidence and risk factors. Med J Armed Focus India.1998; 54: 191 – 195.

15      Raine T, Powell S, Krohn MA. The risk of repeating LBW and the role of prenatal care. Obstet Gynecol. 1996; 84: 485 – 489.

16      Miller LK. LBW and preeclampsia in pregnancies. J Obg. 1994; 84: 946 – 949.

17      Batebi A. Evaluation of behaviors in pregnancies between LBW and normal weight neonates in Tehran in 1996 – 1995 [PhD thesis]. Tehran University of Medical Sciences; 1997.

18      Xiao R, Sorensen TK, Williams MA, Luthy DA. Influence of preeclampsia on fetal growth. J Matern Fetal Neonatal Med. 2003; 13: 157 – 162.

19      Jamal N, Khan M. Maternal risk factors associated with LBW. J Coll Physicians Surgeons Pakistan. 2003; 13: 25 – 28.

20      Schartz R, Sacks P. Etiology and outcome of LBW and preterm infants. Health Econ. 2002; 11: 206.