Association of Maternal Risk Factors with Birth Weight of Newborn in a Tertiary Level Hospital in Dhaka City

Background: Lowbirthweight(LBW)contributes substantially to neonatal, infant, and childhood mortality and morbidity. Several maternal factors contribute to the incidence of LBW, majority of which are biologically and socially interrelated, are modifiable; making LBW a potentially preventable condition. Objective: To evaluate the association of maternal risk factors with birth weight of newborn. Methods: This hospital-based cross-sectional comparative study was conducted in Mugda medical college, Dhaka, a government health center of Bangladesh, from January 2019 to 30 June 2019. A total of 180 recently delivered pregnant mother were included in this study and categorized into two groups: Group A- 90 mother who had given birth of low birth weight baby, and Group B- another 90 mother who delivered normal birth weight baby.Face-to-face interviews using a structured questionnaire and a review of medical records were carried out. Statistical analyses of the results were obtained by using window-based computer software devised with SPSS version 23. Results: Highest percentage of patients from both group A and B were belonged to 20 - 34 years of age (62.2% and 81.1% respectively) and para £ 3 (76.7% and 88.8% respectively) with significant odds ratio for delivering low birth weight baby at advanced maternal age ( ³ 35 years) (OR=2.14, p value 0.037) and high parity (para >3) (OR=2.44, p value 0.03).Majority mothers from group A had hypertension (58.9%) whereas 90% mothers from group B were normotensive with significant odds ratio (OR= 12.89, p value <0.001) as risk factor for predicting low birth weight baby. Multivariate logistic regression analysis revealed that gestational hypertension was the most powerful independent risk factor (OR= 12.72, p value <0.001) for delivering LBW baby compared to age ³ 35 years (OR= 0.757, p value .717) and parity >3 (OR= 2.66, p value 0.257). Conclusion: Gestational hypertension, advanced maternal age and high parity are the significant risk factors for delivering LBW baby. However, further larger multicenter study is recommended.

and a major determinant in the achievement of Millennium Development Goals or MDG. 5 Several factors contribute to the incidence of LBW, which are both maternal and fetal. The majority of the maternal factors, which are biologically and socially interrelated, are modifiable; making LBW a potentially preventable condition. 6,7 Among maternal risk factors, gestational hypertension has been found to be a risk factor for low birth weight. 8 It is estimated that hypertensive disorders in pregnancy complicate approximately 10-16% of pregnancies and are leading causes of maternal, fetal and neonatal morbidity and mortality worldwide. 9,10 It is also estimated that gestational hypertension affects about 5 -8 % of all pregnant women worldwide. 11 Rahman et al found PIH to be an independent risk factor for low birth weight. Women who delivered low birth weight babies were 5 times more likely to have had pregnancy-induced hypertension. 12 Various other factors have wellestablished association with LBW including gestational age, maternal age, low hemoglobin, nonpregnant weight, pregnancy interval, parity, and educational status, violence during pregnancy, tobacco use and very low socioeconomic status. 13,14 However, there is limited study in Bangladesh on maternal risk factors responsible for delivering low birth weight. For better understanding in our country perspective, we conducted this study with an aim to identify the maternal risk factors associated with low birth weight of newborn.

Materials and Methods
Study area and period: This study was carried out in gynecology and obstetrics ward of Mugda Medical College, Dhaka, over a period of six months (January, 2019 to June, 2019).

Study design, source of population and data collection:
This was a hospital-based cross-sectional comparative study. Total 180 recently delivered pregnant mother in Mugda Medical College were included in this study and divided into two groups: group A-90 mother who had given birth of low birth weight baby and Group B-90 mothers who delivered normal birth weight baby. Following informed written consent, detailed history, physical examination and necessary investigations were performed. All patients were interviewed at hospital using a semi structured questionnaire, which was pre-tested at Dhaka Medical College Hospital. Necessary modification was done before the finalization of the questionnaire. It contained sociodemographic variables including age, religion, educational status, occupation and monthly family income. It also contained obstetric history including parity, ANC visit, gestational hypertension, drug & family history of HTN, mode of delivery, sex and weight of baby.
Low birth weight was defined as a birth weight of below 2.5 kg 8 . Pregnancy-induced hypertension was defined as blood pressure of e"140/90 mm Hg or a rise of systolic blood pressure of 30 mm Hg and a diastolic rise of 15 mm Hg on more than 2 occasions after the 20 th week of gestation 8 . Gestational hypertension was confirmed by physicians measuring blood pressure by sphygmomanometer. Weight measurement was done by Electronic and Balance Beam Infants Scale/ Spring Scale.
Ethical clearance: Prior to the commencement of this study, ethical clearance was obtained from the Ethical Committee of Mugda Medical College, Mugda, and Dhaka. Written permission was taken from hospital authority before taking interviews. Study population who fulfilled the selection criteria were enrolled purposively. Perspectives of the study were explained to the respondents in easily understandable local language then informed written consent was taken from each respondent.
Data quality assurance: Data was collected using a pre-tested standard questionnaire. It was ensured that the study participants will be able to understand the questionnaire and answer accordingly. To reduce recall bias, we reviewed medical records to verify information on the patients' obstetric history. All collected data from the interview were recorded in a separate case record form. Strict confidentiality was maintained and data was kept locked under principal investigator. After collection of all the required information, data was checked and verified by investigators.
Statistical analysis: The statistical analyses were carried out by using the Statistical Package for Social Sciences version 24.0 for Windows (SPSS Inc., Chicago, Illinois, USA). Frequency and percentage were used to express categorical variables. Mean and standard deviation were used to express continuous variables. Chi square test and independent sample t test was performed in categorical and continuous comparison, respectively. Box-plot distribution of newborn birth weight according gestational hypertension was performed (figure 3). Point-Biserial correlation analysis was performed to see the correlation of birth weight with maternal blood pressure status. A p value of <0.05 was considered significant.

Results
The highest percentage of patients from both group A and B belonged to 20 -34 years (62.2% and 81.1% respectively) with significant differences in age distribution between groups (p value 0.015) (figure 1).
There were no significant differences between the two groups of patients regarding socio-demographic profile (p value >0.05) (table I).
Majority mothers from both group A and B had para d3 (76.67% and 88.89% respectively) whereas high parity (para >3) was significantly higher among group A compared to group B (23.33% vs 11.11%, p value 0.03). Average ANC visit, distribution of mode of delivery and sex of baby was statistically similar between groups (p value >0.05). Mean birth weight of group A and B were 2.18±0. 23 Figure 1: Age group distribution of study mother (n=180). Group A= mothers who delivered low birth weight baby Group B= mothers who delivered normal birth weight baby * Pearson Chi-squared Test (c 2 ) was performed.      IV).

Discussion
This hospital-based cross-sectional comparative study was conducted to identify the risk factor to deliver a low birth weight baby with a hypothesis that gestational hypertension is more strongly associated with delivering low birth weight baby compared to advanced age and high parity. Total 180 recently delivered pregnant mother were included in this study and categorized into two groups: 90 mothers who had given birth of low birth weight baby were assigned in group A, and another 90 mother who delivered normal birth weight baby were in group B.  16 Similarly, several other studies also confirmed that birth weight decreases as maternal age increases. 17,18 However, in contrast to the current study on the effect of maternal age on birth weight, study done in Nepal found that the relationship between birth weight and maternal age was insignificant. 19 Moreover, several showed that young mothers had greater risk of delivering an LBW baby compared to other age groups. [20][21][22] This difference in effect of maternal age on delivering LBW babies between studies may be due to variation in other maternal factors responsible for LBW baby, such as nutritional status, hemoglobin level, adverse psychosocial factors and violence/abuse during pregnancy. Several studies demonstrated that these factors were associated with LBW. 20,[23][24][25][26] In our study, majority mothers from both group A and B had para d3 (76.67% and 88.89% respectively) whereas high parity (para >3) was significantly higher among group A compared to group B (23.3% vs 11.1%, OR=2.44, p=0.03). Previous research also found that the risk of LBW events was more significant in mothers with high parity. 20,27,28 Rahfiluddin et al found an increase in LBW after fourth parity (51.28%) 28 .   29 This negative effect on birth weight is likely due to the deterioration of endometrial and corpus uterine functions due to too many giving birth, thus affecting circulatory nutrition and consequently susceptible to LBW. 20 We found, majority mother of group A had hypertension (58.89%) whereas 90% mothers from group B were normotensive with significant odds ratio (OR= 12.89, p<0.001) as risk factor for predicting low birth weight baby. Besides, our study revealed that gestational hypertension was the most powerful independent risk factor (OR= 12.72, p<0.001) for delivering LBW baby compared to age more than 35 years (OR= 0.757, p value 717) and parity more than 3 (OR= 2.66, p value 0.257). Like us, a population-based case control study conducted by Rahman et al, found pregnancyinduced hypertension as an independent risk factor (adjusted odds ratio = 5.06; 95% confidence interval: 2.63, 9.71) for low birth weight. 12 A secondary analysis on the role of aspirin for the prevention of eclampsia demonstrated that women with severe pregnancyinduced hypertension without proteinuria had a higher rate of low birth weight than normotensive mothers and those with mild hypertension (p<0.003). 30 A study of Bindu et al. found that the incidence of low birth weight was 70% among PIH group compared to only 16.7% in normotensive group and this difference was statistically significant (p value <0.001) 31 .Afrin et al found gestational hypertension as a strongly significant risk factor for LBW (p value 0.02). 22 Where hypertension is a strongly significant risk factor for LBW (p value 0.02). Matin et al also found the same contributing factor on LBW. 32 The same was documented by several other studies. 4,7,14,17,27 Though, Aleem et al found no significant effect of pregnancy induced hypertension on birth weight of newborn 11 . A Canadian study also showed that infant birth weights were similar between pre-eclamptic and normotensive pregnancy delivered at term. 33 Howbeit, biological mechanisms have been suggested to explain the relation between pregnancy induced hypertension and low birth weight. 12 In a normal pregnancy, the trophoblast cells invade the decidualized endothelium and the inner third of the myometrium. This invasion serves to anchor and connect the placenta with the maternal vascular system. In pregnancy induced hypertension or preeclampsia, it is postulated that the trophoblast invasion into the spiral arteries that supply the placenta is incomplete. 34 Because of the decreased uretro-placental blood perfusion, this leads to intrauterine growth retardation and low birth weight. This "hypoperfusion" model has been supported by many studies. 12,35 There are some limitations in this study as it was done in one hospital so it cannot be true representative of the whole country scenario. As there are several factors interacting in this phenomenon so it is not feasible to single out any particular factor affecting low birth weight. Hence, it is the need of the hour to strengthen the existing maternal services at the community level to prevent and reduce LBW.
Finally, the result will be important to be used by national health policy makers to take early possible measures to reduce rate of LBW and to bring ideas supporting. Early detection of women at high risk of having pregnancy-induced hypertension coupled with more intensive antenatal care may reduce the occurrence of low birth weight. 12 Different components of the disorders of hypertension in pregnancy should also be explored.

Conclusion
This hospital-based case-control study revealed that gestational hypertension, advanced maternal age and high parity are the significant risk factors for delivering LBW baby. Of these, the relationship between gestational hypertension and low birth weight is more strongly associated with low birth weight compared to advanced maternal age and high parity confirming associations in the published literature. Early diagnosis and proper management of gestational hypertension along with appropriate counseling and monitoring in the ante-natal care is recommended to reduce delivery of LBW baby.