Magnitude of fetal macrosomia and its associated factors at public health institutions of Hawassa city, southern Ethiopia

Objectives This study aimed to determine the magnitude of fetal macrosomia and associated factors at public health institutions of Hawassa city, southern Ethiopia. Results In this study, the magnitude of fetal macrosomia found to be 11.86%. Being a male (AOR = 2.2, 95% CI 1.1–4.2), ≥ 37 weeks gestational age (AOR = 6.0, 95% CI 3.1–11.1) and having previous history of fetal macrosomia (AOR = 14.5, 95% CI 7.2–29.2) had a higher odds of fetal macrosomia. Moreover, the magnitude of fetal macrosomia is found be in the global range. Sex of the child, previous history of fetal macrosomia and gestational age were significantly associated with fetal macrosomia. The obstetric care providers should assess all pregnant women for history of fetal macrosomia which would help them to be prepared for the managements of maternal and perinatal complications. Electronic supplementary material The online version of this article (10.1186/s13104-018-4005-2) contains supplementary material, which is available to authorized users.

Compared with developed countries, researches on macrosomia in developing world such as Ethiopia, particularly in the study settings are insufficient. Also, adverse maternal and neonatal outcomes due to macrosomia can lead to additional maternal and neonatal risks in a resource-limited country because of the restricted availability of basic emergency obstetric and newborn care [30]. Understanding certain modifiable risk factors for macrosomia such as high pre-pregnancy body mass index, high blood glucose level during pregnancy and low level of pre-gestational physical activity are crucial for health care providers to prevent macrosomia by  [8,10,11,13,31]. Hence, this study aimed to determine the magnitude of fetal macrosomia and associated factors at public health institutions of Hawassa city, southern Ethiopia.

Study design, setting and population
A cross-sectional study was conducted among women gave birth in public health institution of Hawassa city administration. Hawassa city administration is a capital city of southern Nation, Nationality and People regional state located 275 km south from Addis Ababa, capital city of Ethiopia. The city has been structured by 7 urban sub-cities collectively having 21 kebeles and 1 rural subcity with 11 kebeles. Regarding health institution, the city has 83 health institutions (32 public and 51 private clinics). There are about a total of 852 health professionals working in the randomly selected primary health institution of the city. Together with about 600 health professionals working in Hawassa University comprehensive specialized hospital, the number reached 1452. The source populations were all pregnant women living in the Hawassa city administration. Whereas, the study population were those laboring mother's who attended the randomly selected public health institutions for delivery service during the study period. Mothers with a twin pregnancy were excluded from the study.

Sample size and sampling procedure
The sample size was calculated using single population proportion formula: The proportion (p) = 50% (no published works in the study setting), 95% confidence level = 1.96, 5% of absolute precision. With a non response rate of 10% and a design effect of two for multistage sampling, the total sample size became 580.
Accordingly, multistage sampling technique was employed to include 580 study participants. At first stage, out of the 11 public health institutions, five of them were selected using simple random sampling technique. The selected health institution include: Hawassa University comprehensive specialized hospital, Adare General Hospital, Adare primary health center, Millennium primary health center, and Title primary health center. Then after, the numbers of deliveries' conducted 6 months before the study period in the selected health facilities were assessed to be used as a base to allocate the sample to the selected health facility. So that, the number of deliveries reported from Hawassa University comprehensive specialized hospital was 4780, Adare General Hospital 2022, Adare primary health center 313, Millennium primary health center 311, and Title primary health center 61. Hawassa University comprehensive specialized hospital and Adare General Hospital are the only public health hospitals providing comprehensive essential obstetric care in the city. At the second stage, we applied a systematic random sampling method to identify and include all the study participants. The samples were taken proportionate to the number of expected deliveries from each selected public health institution.

Data collection tools and procedure
Interviewer-administered questionnaire were used to collect data. Relevant literature was reviewed to develop the tool and to include all the possible variables that address the objective of the study [4-8, 10-15, 29-31]. The instrument was first developed in English and translated into Amharic and then back to English to check the accuracy. Before the actual data collection, the questionnaire was tested on 10% of health care providers working in public health institutions of a nearby town called Shashemene.
Every woman who came to the selected public health institution for delivery purpose during the data collection period was interviewed. In addition to the interview, the data collectors abstracted clinical data by reviewing the mother and the babies' medical records. They also measured and confirmed the baby's birth weight, and conducted selected examinations for which they get additional training. The data was collected by 5 B.Sc. female midwives and 5 B.Sc. female nurses after 1-day training about informed consent, techniques of interviewing, data collection procedures, and different sections of the questionnaire. Two health officers were assigned as supervisors for the data collectors. Overall supervision also made by the principal investigator.

Data processing and analysis
All collected questionnaires were rechecked for completeness and coded. Then these data were entered and cleaned using SPSS version 20 for analysis. Bivariable and multivariable logistic regression was employed to identify an association between the independent predictors and the outcome variable. Those factors found with their P-value ≤ 0.20 in the bi-variable logistic regression model were fitted into the multivariable logistic regression model to control the effect of confounding variables. Multivariable analysis using standard logistic regression technique was done to evaluate the independent effect of each covariate by controlling the effect of others. Variable having P-value of less than 0.05 in the multivariable logistic regression analysis was considered as significantly associated factors of fetal macrosomia. The adjusted odds ratios with the 95% Confidence Intervals were reported. Before the actual logistic regression analysis was done, the necessary assumption of logistic regression model was checked by using Hosmer-Lemeshow test of goodness of fit.

Socio-demographic characteristics of the respondents
A total of 580 respondents were included in the study (response rate = 100%). Most of them 560 (96.6%) were married. The majority, 492 (84.6%) were between the age of 20-34 years and more than half, 325 (56%) had primary education. More than two-thirds 456 (78.6%) of the respondents had less than five family size (Additional file 1: Table S1).

Fetal macrosomia and risk factors
In this study, 63 (11.86%) of delivered fetus were macrosomic and 67 (11.55%) of them were low birth weight (< 2.5 kg). About two-thirds, 450 (77.6%) of the newborn baby had a normal birth weight (2.5-3.9 kg). Majority, 465 (80.2%) of the women had preconception Body Mass Index (BMI) of 18.5-24.9. More than half 330 (56.9%) of child's sex were male. Most 519 (89.5%) of the gestational age of the pregnancy were term. Similarly, 540 (93.2%) of the respondents were not diagnosed with any chronic disease. Moreover, 523 (90.2%) of the women had no history of macrosomic infants (Table 1).

Adverse maternal and infant outcome in relation to fetal macrosomia
Most, 57 (10%) of macrosomic infants had normal and alive pregnancy outcome in relation to child. Among women who had normal pregnancy and child birth, 60 (10%) of them were macrosomic. Similarly, 46 (8%) of macrosomic infants had delivered by spontaneous vaginal delivery ( Table 2).

Factors associated with fetal macrosomia
In the bivariate analysis the factors found to be significantly associated with fetal macrosomia were: sex of the child, gestational age, previous history of infant with macrosomia and monthly income. However, in the multiple logistic regression analysis: sex of the child, gestational age and previous history of infant with macrosomia were significantly associated with the magnitude of fetal macrosomia.
In the current study, there is a significant association between sex of the child and macrosomia. Those children who were male had 2.2 times greater odds of macrosomia than those who were female. This is similar with studies conducted in Turkey [10] and China [8,15]. Similarly, being a gestational age of 37 weeks and above was also significantly associated with fetal macrosomia. This is consistent with study done in Norway [32] and Lithuania [6]. Moreover, previous history of macrosomia was significantly associated with fetal macrosomia. This finding is in line with the studies conducted in Iran [11,18] and Lithuania [6].  In this study, the magnitude of fetal macrosomia is found be in the global range. Sex of the child, previous history of fetal macrosomia and gestational age were significantly associated with fetal macrosomia. The obstetric care providers should assess all pregnant women for history of fetal macrosomia which would help them to be prepared for the managements of maternal and perinatal complications.

Limitations
This study has some limitations: Firstly, the study design did not actually investigate for modifiable risk factors such as high pre-pregnancy body mass index, high blood glucose level during pregnancy and low level of pregestational physical activity. Hence, the results of the study had a limited clinical value. Secondly, qualitative aspects of data were not included in this study to explore some determinant factors and to triangulate the finding of the quantitative data. Lastly, as the study is cross-sectional in design, it may not create true causal relationship between fetal macrosomia and its associated factors.

Additional file
Additional file 1: Table S1. Socio-demographic characteristics of women who gave birth in public health institutions of Hawassa (n = 580), South Ethiopia 2017.

BMI: body mass index.
Authors' contributions AKB and BJ: conceived and designed the research study, developed the proposal, and prepared the manuscript. NW: participated in the analysis, drafted the manuscript and revised subsequent drafts of the paper. All authors read and approved the final manuscript.