Macrosomia is usually defined as a newborn weighing 4000 g and above regardless of gestational age and, it was the one adopted in this study, but widely, its definition uses threshold birthweight percentile or birthweight [1]. It is often the result of maternal morbidities like diabetes, obesity [2,3], but can also occur without identified maternal morbidity [4]. Its incidence varies between 2% to 15% in recent publications [5,6], and it is increasing in some countries or regions [7,8] while reducing in others [9]. It is still associated with high morbidity and mortality in Sub Saharan Africa [10,11]. Cameroon is a Sub-Saharan African country at the Gulf of Guinea, with 23 million inhabitants. Macrosomia is also associated with maternal, fetal and post-natal complications such as cephalopelvic disproportion, shoulder dystocia, a higher proportion of cesarean, hypoglycemia, birth trauma [12,13]. The decision concerning the mode of delivery of macrosomic fetus and management remains therefore a challenge in modern obstetrics.

Some authors have shown an association between macrosomia and the increase of shoulder dystocia [12], but others like Sharaf did not [14], revealing the implication of other fetal anthropometric factors determining the most appropriate mode of delivery of the macrosomic fetus. Newborn size at birth is assessed by routine anthropometric parameters and, the objective of this study was to assess the relationship between newborn macrosomic baby anthropometrics parameters and the mode of delivery, in order to improve the mode of delivery-decision making and, therefore, promote more appropriate management of macrosomic pregnancy at term.

It was a descriptive cross-sectional study, with prospective data collection over an eight months period, from November 4^th 2013 to June 4^th 2014 in the Yaounde University Teaching Hospital which is affiliated to the Faculty of Medicine and Biomedical Sciences of the University of Yaounde I and the district Hospital of Biyemassi, a tertiary health facility with the possibility of surgical management of obstetrical complication in the same town.

All macrosomic newborns, defined as birth weight ≥ 4000 g taken at the moment of delivery were included. We excluded macrosomic babies born through the elective caesarian section, multiple pregnancies or from mothers who did not give their written consent. Cases of macrosomia associated with any fetal congenital macroscopic malformations like hydrocephalus, or intra-uterine fetal death before admission and women with protracted pelvis which we defined in this study as true conjugate <10.5 cm (got from clinical pelvis assessment through the formula True conjugate (cm)=Promontory-subpubic distance (cm) minus 1.5 were also excluded.

The data collected were represented by tables and figures and focused on maternal sociodemographic and obstetrical data (age, gestity parity, past history, maternal height). The newborn data assessed were the route of delivery, the anthropometric parameters (cranial perimeter, newborn length, thoracic perimeter…) and the outcome. Data statistical analysis was done using Epi info version 3.5.4, and we used X2 for data distribution assessment and bivariate analysis. A P value <0.05 was the statistical significance threshold, for an interval confidence of 95%. This study received the approval of the ethics committee of the two hospitals and the authorizations of their managers.

We included 77 cases of macrosomic newborn, 1002 deliveries occurred during the same period, thus a macrosomic delivery frequency of 7.68% among which, 10.4% weighed 4500 g and above. The vaginal delivery frequency was 71.4% (55/77).

This study was conducted in a university teaching hospital and in a tertiary medical center with caesarian section and newborn resuscitation capacity. Together they both realize more than 1500 deliveries/year.

The frequency of macrosomia was 7.7% (77/1002), more than twice the incidences found in Tanzania, Australia and higher than a Brazilian study over a 13-year period [15,16]. A similar incidence was recently found in Chad a neighboring country of Cameroon [17]. The incidence of macrosomia varies between 2% to 15% in recent publications [5,18], but an incidence of 20% was found in 2008 in Scandinavia [18]. It is different from one region to another within the same country [7], and even from one hospital to another [19].

Macrosomia has been shown to be related to maternal and fetal factors. Abubakari et al, have shown in Ghana that parity female fetus was significantly associated with decreased risk of macrosomic births [19]. Beyond the shorter time of our study period, parity 1 and female sex represented indeed only 20 and 31% respectively of our sample (Tables 1 and 2). Obesity is another risk factor [20] and only 17% (13/77) had a normal BMI on the day of delivery and, more than half were frankly obese (Table 3), probably preexisting before pregnancy. Macrosomia can also be related to multiparity and macrosomic sibling [12]. Parity>1 represented indeed 80.5% (62/77), and 31.2% (24/77) had previously delivered a macrosomic baby, some of them five times in our study population (Table 1). Maternal height ≥ 1.55 m like nearly 100% of our sample (Table 4) could multiply the risk of the macrosomic baby by five-fold in Peru [21].

Table 1: Obstetrical parameters.

Table 2: Post-partum and post-natal parameters.

Table 3: Maternal parameters on admission.

Table 4: Maternal parameters on admission.

Some other identified factors not analyzed in this study are maternal delivery weight ≥ 80 kg, diabetes mellitus, gestational age ≥ 40 years, post-term, pregnancy weight gain ≥ 18 kg, maternal lifestyle [22-24].

The complications of macrosomia happen mostly during labor, delivery, the post-partum and post-natal periods. The choice of the most appropriate route of delivery is still a challenging moment for any obstetrician. The macrosomic fetus estimated weight has been until today the main parameter of the decision, and many authors have reported a positive correlation between the fetal weight and delivery by caesarian section, even when there was no maternal co-morbidity.

Some authors have indeed shown a relation between dystocia and increasing macrosomic weight [25], interventional deliveries, shoulder dystocia, and genital laceration [26], but we found no relation between fetal weight and mode of delivery (p=0,156, Table 5). Bekdas et al. analyzing 509 macrosomic newborns from non-diabetic mothers with 500 healthy ones, also found no difference in the mode of delivery, [4], revealing the probability of the implication of other fetal anthropometric factors.

Table 5: Relationship between birthweight and mode of delivery.

The macrosomic fetal length (FL) at the onset of labor might be one of the missing ones, as this study seems to show. Our results have shown that 86.4% of macrosomic babies born by caesarian section had a delivery day newborn length less than 53 cm, and only 8.3% of all the macrosomic newborn with an FL ≥ 53 cm was born by caesarian section, and this was statistically highly significant (p<0.0001) (Table 6). This is the very first time this observation is raised.

Table 6: Correlation between newborn length (NL) and mode of delivery.

One hypothesis is that, longer FL increases fetal body mass, sometime reaching the macrosomic threshold ,without additive effect on other fetal body parts, including the bi acromial diameter, leading to vaginal delivery without dystocia or trauma, a longer and thinner “snake-like ” appearance, as compared to FL<53 cm macrosomic newborn, where the excess macrosomic body mass lost in length is manifested in another fetal body part including biparietal or bi acromial, a “wide, thick and short frog-like” effect, leading to mechanic dystocia like shoulder dystocia, an indication of caesarian section. Maternal height is already a suspected risk of macrosomia [21], with a probable possibility of greater risk of the longer, therefore, heavier fetus.

Antenatal Magnetic Resonance Imaging (MRI) technology can nowadays show the whole body of a term fetus, allowing intrauterine measures of other fetal anthropometric parameters including fetal length.

We also noticed that they were a statistical relation-like (p=0.069) between macrosomic newborn fetal length and weight showing that among the 8 fetuses weighing 4500 g and above, 50% measured (51-53) and 50% (53-55), with the TFL value of 53 cm, (Table 7), appearing as a probable decisive threshold value in the prediction of the mode of delivery of macrosomic baby. We didn’t find previous publications to confront findings concerning the implication of fetal length in the determination of the most appropriate mode of delivery of the macrosomic baby. Further and larger scale case-control or cohort studies are of course needed to confirm FL at the onset of labor, in case of suspicion of macrosomia as a predictor of the most appropriate delivery route.

Table 7: Relation between newborn weight and NL.

The frequency of macrosomia was high, probably due to the presence of many previously identified macrosomia favoriting factors in our study population. The fetal length of the suspected macrosomic fetus at the onset of labor, rather than body weight, seemed to be a better predictive parameter to determine the mode of delivery of a macrosomic fetus. In our study population, FL<53 cm at the onset of the labor of macrosomic fetus might increase the risk of delivery by caesarian section, while an FL ≥ 53 cm increases the chance of successful vaginal birth. The way forward is the evaluation and improvement of the accuracy of suspected macrosomic baby intrauterine TFL assessment, using new numeric medical imaging technology like MRI or 4D ultrasound.

MVE KOH Valère did the study design and wrote the article; Belinga Etienne, Jean Paul Engbang and Jean Marie Kasia reviewed and provided critical comments and suggestions for the manuscript.

The authors declare no conflict or competing interest; this work was not sponsored by any organization and was self-financed.

We thank all the team of the two health facilities including the managers who made this study possible