Foetal macrosomia has been defined in different ways. There are considerable variations of the minimum weight that defines macrosomia.¹⁻³ The most satisfactory definitions are a birth weight above the 90th percentile corrected for gestational age and sex or a birth weight of 4000-4500g. Due to the variation of the minimum weight that defines macrosomia, reports of its incidence vary from 3% to 15%.⁴ The incidence also varies with ethnicity. Studies have shown that Chinese and South Asian infants are smaller for their gestational age.⁵ Differences in birth weight distributionare probably due to the genetic and anthropometric factors.⁶ Macrosomia is recognized as a cause of foetal and maternal morbidity and mortality.⁴

Risk factors for macrosomia include high maternal body mass index and weight gain, advanced maternal age, multiparity, diabetes mellitus, and gestational age >41 weeks.⁷ However, it is well known that prediction based on clinical risk factors alone has a very low positive predictive value.⁷

The aim of this study was to determine the incidence of foetal macrosomia and macrosomia-associated maternal morbidity and mortality during a 6 months study at N’Djamena Mother and Child Hospital.

This was a prospective descriptive and analytical study covering the six months from January to June 2016. Our sample consisted of two groups: The study group were mothers who delivered macrosomic babies. We included all live newborn singleton macrosomic who were delivered at or greater than 37week’ gestation and who had no clinical evidence of congenital malformations. The control group were mothers who delivered a baby with a normal weight. These births were recorded after every macrosomia so there were an equal number of mothers in each group.

Demographic data including age, parity, and birth weight were recorded. The outcomes of interest were foetal and maternal complications. Data analysis was done by Epi info 6.0 French. Chi-square (X²) test (p<0.05) was used to compare variables.

Out of 5,284 deliveries during the study period, 403 babies weighed 4.0kg and above. So the incidence of macrosomia was 7.6%.

Maternal characteristics

The mean maternal age and mean birth parity of the study group was significantly greater than the control group. There were significantly more mothers with a previous history of foetal macrosomia in the study group than in the control group (Table 1).

Delivery mode

Table 2 shows that 21.1% of mothers in the study group had delivered by caesarean versus 8.7% in the control group

Maternal complications: The commonest maternal complication in the macrosomic group was postpartum haemorrhage, followed by prolonged labour and perineal laceration-mainly first-and second-degree laceration (Table 3).

Foetal outcome: Table 4 shows that the male/female ratio of the neonates was sifnificantly higher among the macrosomic group than the control group (p=0.037)There was a significantly higher Proportion of macrosomic babies with an Apgar score below seven in the first and in the fifth minute compare to normal babies (p=0.0009).

There were 5 (1.3%) cases of shoulder dystocia in the macrosomic subjects and none in the control group. No foetal births injuries occurred.

There were three stillbirths (0.7%) in the study group and 11(2.7%) in the control group .A difference that was statistically significant (p= 0.032).

There were 34 (8.4%) cases of hypoglycaemia in the macrosomic neonates and 11 (2.7%) in the control group.

Incidence and risk factors

The incidence of foetal macrosomia in this study was 7.6%. A Nigerian investigation reported 8.1%.⁸ The highest reported incidence is 20% in Nordic countries.⁹These figures are influenced by race and local factors.⁸ The pathophysiology of macrosomia is related to the associated maternal or foetal conditions poorly controlled diabetes mellitus, maternal obesity, and excessive maternal weight gain. All of which have intermittent periods of hyperglycaemia.

Our study showed that mothers of macrosomic neonates were significantly older which agrees with other reports.^8,10 Grandmultiparity was found to be strongly associated with foetal macrosomia. These findings are in keeping with those of Mutihir¹¹ and Ezegwui⁸ who showed that there was a higher proportion of multiparity among mothers of macrosomic neonates.

This study demonstrated that a large population of women delivering macrosomic infants had previous a history of delivering a macrosomic infant. Women who previously delivered macrosomic babies are 5–9times more likely to deliver a baby considered large-for-gestational age in subsequent pregnancies.¹²

We found a greater proportion of diabetic mothers among the study group than in the control group. Foetal macrosomia in diabetic mothers has been attributed to poor glucose control. Hyperglycaemia in the foetus results in the stimulation of insulin, insulin like growth factors, growth hormone, and other growth factors, which stimulate foetal growth and deposition of fat and glycogen.

Macrosomia is associated with a higher incidence of Caesarean section delivery (double that among the control subjects) and with birth canal lacerations associated with vaginal delivery.^13,14 This was confirmed in this study with a Caesarean section rate of 23.1% versus 8.7% in the control group. The risk of Caesarean section escalates with increasing birth weight, and the proportion of vaginal instrumental delivery decreases with increasing birth weight.^15,16 The increased Caesarean section rate is a consistent finding in different countries and in different ethnic groups, and the odds are particularly high for primiparous mothers.¹⁵ In macrosomic births, the risk of shoulder dystocia is associated with the need for vaginal instrumental delivery.¹⁶

Maternal complications

Macrosomia was strongly associated with prolonged pregnancy in the study. This was comparable to the findings of Mutihir¹¹ and Spellacy¹³ who observed that macrosomic infants account for about 1% of term deliveries and 3–10% of post-term deliveries. Advanced gestational age results in a larger birth weight. Macrosomia occurs with higher frequency in prolonged pregnancies. This is to be expected as infants gain approximately 150-200g weekly near term. The duration of labour is more prolonged for women carrying macrosomic babies, and the risk is increased with increasing birth weight.¹⁵ Both the first and second stages of labour are longer than for normosomic pregnancies, and arrest of descent in the second stage of labour is associated with macrosomia.¹⁵ Our findings confirm this assertion with the higher prolonged labour in the study group(19.9% versus 5.7%).Macrosomia had been reported as a risk factor for post partum haemorrhage^16,17 a fact confirmed in our study.

Foetal outcome

Male infants are more likely to be macrosomic than female infants. Male infants are generally 150-200g larger than female infants of the same gestational age near term.

Although the literature frequently and consistently demonstrates an increase in perinatal morbidity and mortality with increasing birth weight, the overall incidence of neonatal complications remains low.¹⁸

We had noted a higher proportion of newborns with bad Apgar scores in the study group compared with the control group. Ezegwui⁸ also reported a higher proportion of newborns with bad Apgar scores in their study group. The greater the birth weight, the higher the risk of low Apgar scores.

More newborns with hypoglycaemia were found in the study group. The risk of neonatal hypoglycaemia is higher in heavy babies.¹⁹ Neonates with a birth weight >4,500g had a seven-fold higher risk of having neonatal hypoglycaemia, compared with those with an appropriate weight for gestation age.²⁰ This risk further increases in the presence of gestational diabetes.

Five shoulder dystocia were noted in the study group versus none in the control group. It has been reported consistently in the literature that the risk of shoulder dystocia escalates with increasing birth weight.²⁰ However; the incidence of shoulder dystocia in different birth weight groups varies widely between studies.²⁰

This study had shown that the delivery of macrosomic neonates is anusual activity in our hospital. The risk factors are the same reported as in the literature. The commonest delivery mode is vaginal despite a high proportion of Caesarean section. Main maternal complications are post partum haemorrhage, prolonged labour and perineal laceration. Foetal outcome are a bad Apgarscore, hypoglycaemia, shoulder dystocia and stillbirth. There is a clear need during prenatal care and delivery to minimise maternal and foetal complications.

None.

No financial assistance or grants were solicited or obtained during the course of preparing this article.

We obtained consent of patients and agreement of the Director of N’Djamena Mother and Child Hospital.

Author declares there is no conflict of interest in publishing the article.

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