CONTRIBUTION OF GESTATIONAL WEIGHT GAIN TO FETAL BIRTH WEIGHT AMONG PREGNANT WOMEN IN A PUBLIC TERTIARY HOSPITAL

Background: The ideal gestational weight gain (GWG) to ensure a favorable neonatal birth weight remains arguable but the desired birth weight for optimal early life adaptation and subsequent seamless childhood navigation is no longer in doubt. Objective: We sought to document the role of GWG on birth weight and to examine the influence of some materno-fetal variables. Method: The case records of patients who initiated antenatal care in the first trimester and delivered in University of Benin Teaching Hospital, Benin City from January 2014 to December 2017 were retrospectively studied. Data on sociodemographic characteristics, clinical management and outcome were extracted and analyzed. Results: The frequency of early booking was 14.5%. Mean GWG was 7.7±5.8kg and the mean birth weight was 3.1±0.4kg. GWG did not significantly influence birth weight. Social class was significantly associated with birth weight (P<0.001). Weight gain less than 5kg with OR of 1.52 (CI=1.02 to 2.04; P=0.042) and lower social class with OR of 1.81 (CI=1.23 to 2.57; P=0.02) predicted birth weight lower than 2.5kg. Maternal age, parity and fetal sex did not significantly impact on birth weight. Conclusion: Overall GWG in our study was poor but this did not significantly influence birth weight. GWG in the third trimester impacts on fetal growth, and low birth weight can be predicted by GWG lower than 5kg. A focus on improved GWG in the prenatal period to optimize birth weight appears necessary. We recommend nutritional counselling and support especially in the second half of gestation.

The IOM/NRC recommendation for GWG is based on maternal weight at the start of pregnancy.Underweight women are expected to gain more than overweight and obese women, while normal weight woman should attain GWG lying between the other categories.These recommendations have clearly highlighted that extremes of weight in pregnancy impact negatively on fetal outcome viz.increased risk of intrauterine growth restriction and preterm delivery in those with inadequate weight gain, while excessive weight gain in pregnancy has been correlated with larger birth weights and the 1-3 attendant consequences.Maternal weight assessment is a cheap and reliable means of assessing fetal growth, thus providing a surrogate fetal surveillance modality for predicting low birth weight neonates and subsequent adverse perinatal outcome.The role of maternal anthropometric variables in predicting pregnancy 1-5 outcome has been extensively studied elsewhere, but there is need to direct more attention to this very important area of research in developing countries, considering the significant conflict in previous reports on the effect of maternal weight on birth Ultrasound scan examination coupled with astute clinical observation remains the basic modality for determining fetal growth and wellbeing.Yet this useful tool is not always at our disposal in resourceconstrained settings.Hence, many clinicians now consider routine weight gain monitoring to predict fetal growth and wellbeing as a useful inexpensive intervention, considering its potential for widespread utilization.Previous studies have shown the determinants of birth weight to include maternal prepregnancy weight, GWG, fetal sex, length of the pregnancy in addition to inherent fetal programming for growth, and intercurrent feto-

RESULTS
Of the 8,926 women who delivered during the period covered by the study, 14.5% (1,294/8,926) of them had initiated antenatal care in the first trimester.The records of a total of 420 women were included in the study, giving an inclusion rate of 32.5%.
The mean age was 29.6± 4.35 years with over 61% of them in age group 21 to 30 years.Women less than 20 years or more than 39 years contributed 1.4% each.Almost 80% of the women had parity of 0 or 1, with para 5 making up 2.9%.Majority (89.9%) of the women were in upper social class while 2.3% were in lower social class.(Table 1) With respect to prepregnancy BMI, 27.9% of the women were underweight, 38.1% had normal BMI, and 25.0% were overweight while 9.0% fell into the category of obesity.The maternal weight change (MWC) during pregnancy was more likely to reflect gain than loss (85% vs 5%, respectively), with the GWG through the trimesters of pregnancy, gestational age at delivery, neonatal birth weight as well as neonatal sex.Our primary outcome measure was the overall GWG.Secondary outcome measures included the trend in maternal weight changes, fetal outcome, mode of delivery and birth weight.Factors considered as confounders included maternal age, parity, social class, gestation at delivery and fetal sex.
The information used to generate a database for analysis was retrieved from our departmental electronic data records, patients' case notes as well as records of the theatre and labour ward.The sociodemographic and clinical information was subjected to statistical analysis with a personal computer using SPSS version 20.0 (SPSS IBM Corp, Armonk, NY) and GraphPad InStat 3 (GraphPad Software Inc., San Diego, CA).Univariate analysis was conducted using Chisquare test or Fisher's Exact Test as appropriate.
Cross tabulations and Pearson correlation were used to determine associations while binary logistic regression was conducted to determine More of the weight gain was observed in the third trimester than second trimester (1.84kg per week for GWG of 4.8kg vs 0.55kg per week for GWG of 2.9kg, respectively).Women with normal BMI gained the largest weight (9.2±4.5kg)followed by those who were underweight (7.5±4.1kg), and next were the category of obese women (7.2±3.5kg)before the overweight women (7.1±3.8kg).The overweight and obese women had GWG within the recommended range for their categories, giving a 34% rate of adequate GWG.
There were 420 babies born to the women studied, out of which 53.6% (225/420) were males, 76.2 (320/420) were delivered vaginally, with a mean birth weight of 3.1±0.4kg.The present study showed that third trimester weight gain had significant impact on the birth weight of babies but the same effect was not found for GWG in the second trimester of pregnancy.This 14 is in contrast to the report of Onwuka et al who found that excessive weight gain in the second trimester was associated with large babies while poor GWG also in the second trimester predisposed 25 to low birth weight.However, Sridhar et al in their study reported that the trend in weight gain in both second and third trimesters was likely to impact on the birth weight when the GWG is observed to be above the IOM/NRC recommendation for the BMI of the woman.It appears reasonable to expect significant impact on fetal weight when GWG exceeds a certain threshold in both the second and third trimesters, or if GWG remains below a critical 22 level.The lack of association between GWG and birth weight in the second trimester in the present study is likely reflective of the overall poor weight gain in our population of patients.The roles of parity, maternal pre-pregnancy BMI and GWG on birth weight and risk of preterm birth 26,27 have previously been established.In the present study, low parity women were more likely to book early, whereas higher parity women delayed initiation of antenatal care, hence GWG and birth weight comparison based on parity will appear skewed.However, parity did not significantly influence the trend of MWC, nor did it affect the birth weights of the babies.The social status of clients has been suggested as one of the determinants of pre-pregnancy BMI and GWG as well as fetal outcome.In the present study, lower social class was significantly associated with 23 lower birth weight.Similarly, Kehinde et al found a negative impact of lower social class on birth 5 weight.In contrast, Gaillard reported a link between low income or education and maternal obesity in a European population, while Wright et 28 al found little influence of socioeconomic status on birth outcome.The high proportion of women of upper social class in our study may be due to the urban location of our hospital.It is also possible that upper social class women with better education and favoured occupations are more likely to patronize a university hospital which is often viewed as a facility meant for the elite.Furthermore, the women with upper social class may also exhibit a better health-seeking behavior of early booking for antenatal care.
In this study, we have shown that the majority of women attending antenatal care in UBTH tended to initiate antenatal care beyond the first trimester, especially among the older multiparous clients.The average GWG was much lower than the IOM/NRC recommended range for underweight and normal BMI categories but this observation did not impact negatively on the mean birth weight of their infants.Furthermore, maternal age, parity and social class were not significantly associated with GWG, but birth weight was lower with lower social class.It is known that birth weight is determined by many factors during pregnancy in addition to the role played by GWG.Hence when GWG is marginal especially in low parity women who initiate antenatal care early, the birth weight at term may be more influenced by factors other than prepregnancy BMI or GWG.Therefore, future research interest in this area will attempt to focus on birth weight determinants with particular emphasis on n u t r i t i o n a l , e n v i r o n m e n t a l , s o c i a l a n d psychological variables.We found that birth weight was not significantly influenced by GWG.Despite the inherent limitations of a retrospective design, the information captured in our electronic database was easily accessible for the period studied.However, our study population was largely skewed toward the small proportion of women who commenced antenatal care early.

7weight.
Costa et al working in Brazil demonstrated an association between maternal obesity and fetal macrosomia, similar to the reports by Ezeanochie et 8 9 al and Iyoke et al in Nigeria, who both noted 10 obstetric complications traceable to obesity.Ugwa in Nigeria also found maternal weight to be significantly correlated with birth weight.In 11 contrast, Aisien and Olarewaju in their study did not document any significant effect of maternal weight on birth weight.
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