Journal of Womens Health, Issues and Care ISSN: 2325-9795

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Research Article, J Womens Health Issues Care Vol: 4 Issue: 5

Maternal Body Mass Index and Weight Gain in Relation to Low Birth Weight: A Study from Eastern Thailand

Panya Sananpanichkul1* and Sinitdhorn Rujirabanjerd2
1Department of Obstetrics and Gynecology, Phrapokklao Hospital, Chanthaburi, Thailand
2Department of Pathology, Faculty of Medicine, Prince of Songkhla University, Songkhla, Thailand
Corresponding author : Panya Sananpanichkul
Department of Obstetrics and Gynecology, Phrapokklao Hospital, Chanthaburi, Thailand
Tel: 6681-862-3992
E-mail: [email protected]
Received: June 21, 2015 Accepted: October 01, 2015 Published: October 04, 2015
Citation: Sananpanichkul P, Rujirabanjerd S (2015) Maternal Body Mass Index and Weight Gain in Relation to Low Birth Weight: A Study from Eastern Thailand. J Womens Health, Issues Care 4:5. doi:10.4172/2325-9795.1000204


Maternal Body Mass Index and Weight Gain in Relation to Low Birth Weight: A Study from Eastern Thailand

Introduction: This retrospective study aimed to determine the association of maternal factors and low birth weight newborns at Phrapokklao hospital. Material and Methods: We recruited 1,968 pregnant women delivering babies after 34 weeks of gestation during January 1, 2013 to June 30, 2013. Data collected included fetal weight, maternal age, parity, gestational age, prepregnancy weight, body mass index (BMI), weight gained during pregnancy, hematocrit, place of residence, maternal HIV infection and completion of antenatal care visits. Results: Fifty eight percent of the women had a normal BMI and 65.7% were between 20-34 years old. Pregnancy weight gain categorized by BMI showed that the percent of women in the under, normal, and over-normal ranges were 37.0%, 33.3% and 29.7% respectively. Maternal prepregnancy BMI did not associated with low birth weight newborns (LBWN) or small for gestational (SGA) newborn. Nulliparity and low gestational weight gain was 1.8 and 3.5 times greater risk (adjusted OR 1.814, 95%CI 1.232- 2.671, p-value=0.003 and adjusted OR 3.477, 95%CI 2.132-5.668, p-value=0.001 respectively) of having a LBWN. While low weight gain pregnant women had 6.3 more risks (adjusted OR 6.325, 95%CI 1.437-27.836, p-value = 0.015) of having SGA newborn, it showed protective effect for LGA newborn. The results between using IOM 1990 and 2009 recommendations remained the same irrespective of the different guideline used. Conclusion: Nulliparity and low gestational weight gain were all directly associated with LBWN while low maternal BMI and low gestational weight gain showed protective effect for LGA newborn.

Keywords: Low birth weight; Pregnancy weight gain; Pre-pregnancy BMI; IOM 1990; IOM 2009; Small for gestational age; Large for gestational age


Low birth weight; Pregnancy weight gain; Pre-pregnancy BMI; IOM 1990; IOM 2009; Small for gestational age; Large for gestational age


Newborn birth weight reflects maternal health and nutrition during pregnancy. It is also an indicator of newborn survival, health, and social and behavioral development. The World Health Organization and United Nations Child’s Fund define low birth weight (LBW) as weight at birth of less than 2,500 grams regardless of gestational age [1].The mortality rate of low birth weight newborns (LBWN) is higher than normal weight newborns. LBW is one of the most common causes of perinatal mortality [2-4].
LBWN can be the result of either preterm birth (born prior to 37 weeks of gestation), intrauterine growth restriction (IUGR), or both. IUGR is a major concern of LBWN because the mortality rate of IUGR infants is fairly high during the first year of life [5]. These infants also have higher morbidity and a higher chance to have impaired growth and/or cognitive and motor system development than normal infants [6]. Additionally, these IUGR newborns are also at risk of having a lower-than-normal intelligence quotient (IQ), and of developing several medical problems later in life [7] such as hypertension, heart disease, diabetes mellitus, or infective diseases.
Various conditions are associated with LBWN notably primiparity, teenage pregnancy, low prepregnancy weight, low prepregnancy body mass index (BMI), pregnancy weight gain of less than 10 kg and incomplete antenatal care (ANC) [8-10]. These factors vary from region to region [11].
Phrapokklao Hospital in Chanthaburi province is the second largest government hospital in the eastern part of Thailand. It is located approximately 100 km. from the Thai-Cambodian border. This hospital serves as one of the major referral centers for advanced treatment from other community hospitals in the province. The objective of this study was to determine the association of various maternal factors and LBWN at Phrapokklao Hospital.

Materials and Methods

This retrospective study was approved by the Phrapokklao Hospital Ethics Committee. Data of all pregnant women delivering a baby after 34 weeks of gestation during January 1 - June 30, 2013 was collected from the hospital medical records. Since fetal lung maturity is generally sufficient after 34 weeks of gestation, babies delivered before this time were excluded to eliminate some confounding factors from premature birth. Multifetal pregnancies, macrosomia and cases of dead fetus in utero were also excluded from this study. The data for each mother collected were maternal age, parity, gestational age at delivery, hematocrit during third trimester, prepregnancy weight, and weight gained during pregnancy, birth weight of the newborn, place of residence, fetal presentation at birth, maternal HIV infection and completion of antenatal care. Associations between these factors and LBWN were subsequently studied.
Prepregnancy BMI was defined as maternal prepregnancy body weight in kilograms (kg) divided by the square of the height in meters (kg/m2). Individuals with a BMI <18.5, 18.5-24.9, 25-29.9 and > 29.9 is considered underweight, normal, overweight and obese respectively. Categorization of weight gain during pregnancy was performed following the weight gain recommendations for pregnancy guideline from the U.S. Institute of Medicine of the National Academies [12]. According to this guideline, an appropriate pregnancy weight gain is 12.5-18 kg, 11.5-16 kg, 7-11.5 or 5-9 kg in those with underweight, normal weight, overweight or obese BMI respectively [13]. Pregnant women gaining less weight than the recommendation for each BMI subgroup were classified as ‘under’ normal range. And if their pregnancy weight gain was more than the recommendation, they were classified as ‘over’ normal range [12-13].The rate of weight gain during 2nd and 3rd trimester of pregnancy recommended by IOM 2009 was not included in this study because of limitation of the data. Small gestational age (SGA) refers to the newborn birth weight below the 10th percentile for gestational age while large for gestational age (LGA) refers to the newborn birth weight above the 90th percentile for gestational age.
Data were analyzed using the Statistical Package for the Social Sciences Version 17 (SPSS Inc, Chicago, USA). Maternal and newborn data were compared between LBWN and normal weight newborns (NWN) using unpaired t-test, chi-square test and multivariate logistic regression. A p-value of <0.05 was considered statistically significant.


A total of 1,968 pregnant women were included in this study, with a mean maternal age of 26.9 ± 7.0 years. Most participants were multiparous (63.0%) and 18.1% were teenage pregnancies. Half of them resided in a rural area. The prevalence of maternal HIV infection was 0.9% and 13.2% of the participants were anemic. Only 64.6% of the cases had completed an antenatal program. Ninety five percent of the fetuses were cephalic presentation at birth and 7.4% had low birth weight. Seven point two percent were delivered after 34 weeks of gestation but prior to term. Fifty eight percent of the women had a normal prepregnancy BMI. Categorization of weight gain during pregnancy according to BMI showed that 37.0% were under the normal range while 29.7% were over the normal range. The data showed that parity, gestational age at delivery, and weight gain during pregnancy were all statistically significant contributors to an increased rate of LBWN. Other factors such as completion of antenatal care visits, fetal presentation at birth, place of residence, maternal anemia and HIV infection were not significantly related to LBWN. A summary of the results is shown in Table 1.
Table 1: Comparison of maternal factor according to newborn birth weight. (n=1968)
The characteristics of the LBWN and NWN groups were compared. The mean newborn birth weights between the LBWN (2286.4 ± 202.9) and NWN groups (3118 ± 375.1) were statistically significantly different (Table 2). Non-cephalic presentation of the fetus at birth was higher in the LBWN group (8.2%) than in the NWN group (4.8%). The newborn lengths and head circumferences were significantly smaller in the LBWN group than in the NWN group, and newborns in the LBWN group had a significantly lower 1-minute APGAR score than those in the NWN group (Table 2).
Table 2: Comparison of newborns’ characteristics according to birth weight. (n=1968)
Delivery between 34-36 weeks of pregnancy had 16.25 times more risk for having LBWN (adjusted OR 16.247, 95% CI=10.621- 24.854, p-value<0.001) . Maternal weight gain during pregnancy was associated with newborn birth weight (Table 1). When weight gain during pregnancy was categorized by maternal BMI, we found that if maternal weight gain was less than the recommended values, the infants had 3.48 times more risk of having low birth weight (adjusted OR 3.477, 95% CI=2.132-5.668, p-value<0.001) and 6.33 times more risk of having SGA newborn (OR 6.325, 95% CI=1.437-27.836, p-value=0.015) while it showed protective effect of having LGA newborn (adjusted OR 0.527, 95% CI=0.370-0.751, p-value<0.001) (Table 3). If the maternal gestational weight gain is in “over” categorization, the infant had 1.67 times more risk to be a LGA neonate ( adjusted OR 1.673, 95% CI=1.235-2.264, p-value=0.001).Too much weight gain did not significant relate to LBWN nor SGA newborn.
Table 3: Adjusted Odd Ratio of risk factors for LBWN, SGA and LGA newborn.
Nulliparity had 1.8 times more risk to develop LBWN in our study (adjusted OR 1.814, 95% CI=1.232-2.671, p-value=0.003) and inversely had protective effect of having LGA newborn (adjusted OR 0.476, 95% CI=0.351-0.644, p-value<0.001) (Table 3). This is the same as previous report (Hung TH et al, 2013) that nulliparous be the risk factor for LBWN. Pre-pregnancy BMI did not have an effect on LBWN or SGA newborn in our study. Only when maternal prepregnancy BMI was considered to be underweight (BMI<18.5), that seemed to be a protective factor for LGA newborn (adjusted OR 0.495, 95% CI = 0.319-0.767, p-value =0.002), whereas prepregnancy BMI of overweight and obesity group (BMI>24.9) was not the risk for LBWN, SGA and LGA newborn (Table 3).
Comparing the effect of parity, maternal prepregnancy BMI and weight gain during pregnancy to the birthweight of newborn between IOM 1990 and 2009 weight gain guidelines was showed in table 3.When using IOM 1990 recommendation, nulliparity showed 1.7 times more risk of having LBWN (adjusted OR 1.706, 95% CI = 1.151-2.527, p-value =0.008). Under weight gain during pregnancy and delivery before 37 weeks gestation showed 3.4 and 15.8 times more risk of having LBWN (adjusted OR 3.404, 95% CI = 2.087-5.553, p-value <0.001 and adjusted OR 15.830, 95% CI = 10.393-24.110, p-value <0.001). There was no difference in trend of the result from both recommendations (Table 3).


Low newborn birth weight is widely used as an indicator of public health effectiveness since it can reflect poor maternal health and lifestyle, inadequate nutrition and poor health care during pregnancy. In Thailand, newborns who weigh less than 2,500 g. are considered as having low birth weight by the WHO definition. In this study, only cases with at least 34 weeks of gestation at the time of delivery were included since these infants have a high chance of survival due to sufficient lung maturation, and also to eliminate other possible confounding factors from premature birth. Of all newborn infants observed, 7.2% had low birth weight. This figure is lower than what reported in Thailand by the World Bank (9%) and lower than the worldwide incidence (15.5%) [1]. Although the Thai Ministry of Public Health had a goal of reducing the incidence of LBWN to only 7% by the year 2012 (Department of Health, 2015), this goal has not yet been achieved.
Several factors can directly cause low birth weight in the newborns, particularly poor maternal life-long nutritional status, especially during pregnancy, small maternal physique, teenage pregnancy, alcohol, tobacco or drug consumption, maternal illness during pregnancy, short duration of pregnancy and low socioeconomic status [11].
As the second largest government hospital in the eastern part of Thailand, our obstetric unit aims to promote the well-being of pregnant mothers to achieve outstanding newborn health. However, our study found that approximately one-third of pregnant women did not complete their antenatal care visits, although we also found that incomplete antenatal visits did not have a significant effect on the risk of having a LBWN. This finding is in contrast to the [10].which reported that antenatal visits were a significant factor in promoting mother-child well-being and associated with having normal-weight infants. Women with incomplete antenatal visits in our study also failed to benefit from the hospital educational sessions about mother and fetal care. Integration of an intensive maternal health-care program as a part of Thailand’s primary care system may benefit the country in the long run.
Several previous reports have showed that mothers who were born prematurely had a higher risk to have a LBWN [14].An earlier study found that in countries with low per capita income, 12% of newborns were premature, while only 9% of babies were preterm in countries with higher income per capita [15]. In Thailand, the incidence of preterm infants increased from 9.44% in 2004 to 13.70% in 2010 [16].slightly higher than the incidence of LBWNs previously reported. Delivery at gestational age below 37 weeks in Qatar was 19.6 times to have a LBWN [14]. Compared to 16.2 times from our study (Table 3), although there were some difference in the population included.
Previous studies reported poor prepregnancy nutritional status and small maternal physique could affect newborn birth weight [11]. A systemic review and meta-analysis showed that underweight women had 1.64 times increase risk of a LBWN [17] but this was not exactly the case in our study. Maternal prepregnancy BMI categorized as underweight seemed to have no effect in terms of increase the risk of having a LBWN or SGA newborn. Nevertheless it showed protective effect for LGA newborn (adjusted OR 0.495, 95% CI=0.319-0.767, p-value<0.001) (Table 3). Since underweight is an important indicator of poor nutritional status, it should have some negative effect to the newborn birthweight. Our study only showed that it is difficult for thin pregnant woman to give birth of a LGA newborn. Overweight mother seemed to have no significant effect for LBWN and SGA newborn (Table 3). Being a nulliparous mother had an adverse effect on fetal weight and took 1.8 times more risk for LBWN from our study.
Weight gain during pregnancy played the important role to fetal birthweight especially when it was “under” weight gained group. Of the maternal weight gain during pregnancy, we found the women in ‘under’ group were 3.48 times more likely to have a LBWN. Poor weight gain during pregnancy in every BMI group took more risks for LBWN and SGA newborn, moreover, poor weight gain made it hard to give birth of LGA newborn. Over weight gain during pregnancy had 1.67 more risk to LGA newborn. This was the same trend reported by Erika O [18]. Lack of adequate nutritional knowledge could result in poor maternal-fetal well-being. As suggested earlier, integration of an intensive maternal health-care program as part of Thailand’s primary care system may help with this issue.
As many researches that question about the appropriateness of the weight gain guideline recommendation [19]. We compare the effect of parity, prepregnancy BMI and gestational weight gain of each BMI group to LBWN, SGA and LGA newborn using the IOM 1990 to IOM 2009 guideline (Table 3). The results remained the same irrespective of the different guideline used. This meant that nulliparity, low weight gained during pregnancy and preterm delivery increase risk of having LBWN in both guideline recommendations. We further selected the cases who deliver NBW newborns and subgroup them by BMI to normal weight, underweight and overweight-obese using the guideline recommended by IOM 1990 and IOM 2009 (Table 4). Percent of normal BMI pregnant women that give birth of NBW newborn according to IOM 1990 is 49.4% compare to 57.6% of IOM 2009. We think that the recommendation of weight gain from IOM 2009 is more suitable for our population.
Table 4: Comparison of BMI of pregnant women who delivery normal birthweight neonate between IOM weight gain recommendation 1990 and 2009.
There are several limitations in our study. First, there are no factors such as education, economic status, alcohol, tobacco and drug consumption that may associate to the LBWN [11]. That is because of the limitation in our retrospective data. Second, prepregnancy weight was self-reported in the first time when attend the antenatal clinic. This might have been subject to recall bias. Further research is required to complete the data and to determine the range of weight gain during pregnancy that minimized the risk of having LBWN, SGA and LGA newborn among Thai women whose BMI, in general is lower than Caucasian.
In conclusion, this study showed that maternal factors associated with having LBWN at our provincial hospital were slightly different from other previous reports. Gaining weight during pregnancy less than recommended were directly associated with a high risk of having a LBWN and SGA newborn, while being a nulliparous mother take more risk of a LBWN but not SGA newborn. Prepregnancy BMI does not associate with LBWN or SGA newborn and thin mother was protective effect of having a LGA newborn. The results from this study will certainly be useful for planning health promotion programs for the eastern region of Thailand.


Funding for this project was provided by the Research Institute of Phrapokklao Hospital. We would like to thank Associate professor Dittakarn Boriboonhirunsarn MD., PhD. for useful comments and suggestions.

Conflict of interest

The authors report no potential conflicts of interest relevant to this article.


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