What are the Risk Factors for ≥ 4500 g Macrosomia ?

Objective: To identify risk factors for ≥4500 g macrosomic babies given that maternal and neonatal complications of macrosomia increase with birth weight. Design: Cross sectional analytical study. Setting: The Yaoundé University Teaching Hospital and Central Maternity, Cameroon from October 1st, 2012 to June 30th, 2013. Population: 42 women who delivered ≥4500 g babies and 126 women who delivered babies of 4000 to <4500 g were recruited. Methods: Data were analysed using SPSS 18.0. Analyses included the student t-test and the Fisher exact test. The level of significance was P<0.05. Main outcome measures: Fetal sex and birth weight, gestational age at delivery, maternal age at delivery, parity, mother's pre-gestational body mass index (BMI), weight gain during pregnancy, father's BMI and past history of ≥4000 g macrosomia. Results: Main risk factors for ≥4500 g macrosomic babies were maternal weight gain of ≥16 kg (OR 4.2, 95%CI 2.0-8.9), maternal age ≥30 (OR 3.8, 95%CI 1.8-8.2), post term (OR 2.3, 95%CI 0.9-5.6), past history of ≥4000 g macrosomia (OR 1.9, 95%CI 0.9-4.1) and male sex (OR 1.3, 95%CI 0.6-2.8). Conclusion: To reduce the risk of ≥4500 g macrosomic babies, women at risk should make efforts to gain less than 16 kg bodyweight during pregnancies. Moreover, post term pregnancies should be avoided. DOI : 10.14302/issn.2381-862X.jwrh-14-532 Correspondence to: Dr. Elie Nkwabong, P.O. Box 1364 Yaoundé, Cameroon, Tel: (237) 99663843, Fax: (237) 22312567, Email: enkwabong@yahoo.fr Running title: Risk factors for macrosomia.

Given that complications of macrosomia increases with fetal weight (1,13), knowing in our environment risk factors for macrosomia of ≥ 4500 g might help us taking more care during antenatal care to reduce its incidence and also to be more vigilant during labor, hence, reducing the prevalence of the so many complications mentioned in the literature.The aim of this study therefore was to identify risk factors for macrosomia of ≥4500 g in our country.

Material and methods
This cross sectional analytical study was conducted in the maternities of the University Teaching Hospital and

Results
Forty two women who delivered newborns with birth weight ≥ 4500 g and 126 other women who gave birth to newborns with birth weight between 4000 g inclusive and 4500 g exclusive were recruited.
Birth weight varied between 4500 and 4800 g among the case group with a mean of 4610 ± 69 g as compared to a range from 4000 to 4476 g with a mean (23.8%) in the control group (OR 1.9, 95% CI 0.9-4.1,P=0.10).

Discussion
Macrosomic babies with birth weight ≥ 4500 g were more encountered among male sex than among female sex (OR:1.3,95%CI 0.6-2.8).The ability of male sex for rapid weight gain than female has been observed by many authors (4,5,10).
Mean maternal age for women who delivered ≥ 4500 g macrosomic babies (29.2 years) was significantly higher than that of controls (25.3 years) (P=0.0002).When women aged ≥ 30 years were compared to those of <30 years, the OR for delivering a macrosomic baby of ≥4500 g was 3.8 (95%CI 1.8-8.2).This has already being shown by some authors who noticed that advanced maternal age was a risk factor, especially women aged 30 to 40 were at increased risk (4).Our study found no relation between parity and macrosomia.This is in contrast with the findings of other authors who observed that multiparity was a risk factor (4,5).This discrepancy might be due to our small sample size.
Macrosomic babies who weigh 4500 g or above are not common in our environment.This low prevalence might Regarding pre-gestational BMI, we observed that ≥4500 g macrosomic babies were more frequent among women with mean BMI of 27 kg/m2.This value is a bit higher than the value of pre-gestational BMI ≥25 kg/m 2 found by Heiskanen et al in women delivering ≥4500 g macrosomic babies (10).In our series, when women with BMI ≥30 were compared to those with BMI <25, the OR for delivering a macrosomia of ≥4500 g was 1.5 (95%CI 0.5-4.5).This shows that obese women had increased risk of delivering ≥4500 g macrosomic babies than women of normal BMI.Paternal BMI was found in our study to have no influence in the occurrence of ≥ 4500 g macrosomia (OR 1.0, 95%CI 0.4-2.4).
Women with past history of delivery of ≥ 4000 g macrosomic babies were more at risk than controls (OR 1.9, 95%CI 0.9-4.1).This is not surprising given that in the same woman birth weight generally increases in subsequent deliveries.A woman who has delivered a baby of 4100 g might deliver another of ≥4500 g in the subsequent pregnancies.Other authors found that past history of delivery of a ≥4500 g macrosomic baby was a significant risk factor for the delivery of such macrosomic baby in subsequent pregnancies (5,10).
Increased maternal weight gain during pregnancy was a risk factor for ≥ 4500 g macrosomic babies in our study.
Indeed, when weight gain ≥16 kg was compared to <16 kg, the OR for delivering a ≥4500 g macrosomic baby was 4.2 (95%CI 2.0-8.9).This has already been found by some authors who observed that excessive weight gain was a risk factor (5).This means that increased nutritional input during pregnancy might also be a risk factor for macrosomia.
In our study, gestational age at delivery had an influence on the occurrence of macrosomia since post term (>42 weeks gestation) deliveries were more associated with ≥4500 g macrosomic babies than controls (OR 2.3, 95%CI 0.9-5.6).Some authors too found that prolonged gestation was a risk factor for ≥ 4500 g macrosomia (5).Specifically, a gestational age at delivery > 41 weeks was a risk factor for some (4) while for others it was a gestational age > 42 weeks (10).

Conclusion
Main risk factors for ≥4500 g macrosomic babies as shown in this study were maternal weight gain during pregnancy of ≥16 kg, maternal age ≥30 years, past history of ≥4000 g macrosomia, post term and male sex.
Henceforth, to reduce the risk of delivering those large babies, mothers at risk should try to gain less than 16 kg bodyweight during pregnancies.Furthermore, post term should be avoided.

Table 2 :
Distribution of maternal pre-gestational body mass index BW: Birth weight, BMI: Body mass index.126 (100) Vol-1 Issue 1 Pg.no.-4 macrosomic babies and among 31 women (24.6%) in the control group.It was also noticed in the macrosomic group 20 women (47.6%) whose husband BMI was <25 as against 64 (50.8%) in the control group.OR for ≥

Table 3 :
Distribution of maternal weight gain during pregnancy