Risk in the vaginal delivery of the large fetus

Fetal macrosomia: risk factors and outcome. A study of the outcome concerning 100 cases >4500 g

OBJECTIVE

Because difficult vaginal delivery is more frequent with macrosomic fetuses, some authors recommend routine caesarean section for the delivery of fetuses >4500 g. The purpose of this study was to evaluate the appropriateness of this recommendation, in particular, to analyze maternal and fetal complications according to the mode of delivery.

METHOD

Maternal and neonatal records of 100 infants with weights of at least 4500 g were identified retrospectively from January 1991 to December 1996. Outcome variables included the mode of delivery and the incidence of maternal and perinatal complications.

RESULTS

The study sample consisted of 100 infant and mother pairs. Macrosomic fetuses represented 0.95% of all deliveries during this period and only ten were >5000 g. Mean birth weight was 4730 g (maximum, 5780 g). Gestational diabetes was present in nineteen patients. Diabetes was present in three patients. A trial of labour was allowed in 87 women, and elective caesarean delivery was performed in thirteen patients. The overall cesarean rate, including elective caesarean delivery and failed trial of labour, was 36%. Of those undergoing a trial of labour, 73% (64/87) delivered vaginally. Shoulder dystocia occurred fourteen times (22% of vaginal deliveries) and it was the most frequent complication in our series. There were five cases of Erb's palsy, one of which was associated with humeral fracture, and four cases of clavicular fracture. By three months of age, all affected infants were without sequelae. There was no related perinatal mortality and only two cases of birth asphyxia. Maternal complications with vaginal delivery of macrosomic infants included a high incidence of lacerations requiring repair (eleven cases). No complications were noticed in the patients who had a caesarean section.

CONCLUSION

Vaginal delivery is a reasonable alternative to elective cesarean section for infants with estimated birth weights of less than 5000 g and a trial of labour can be offered. For the fetuses with estimated birth weight >5000 g, an elective caesarean section should be recommended, especially in primiparous women.

Must macrosomic fetuses be delivered by a caesarean section? A review of outcome for 786 babies greater than or equal to 4,500 g

Because difficult vaginal delivery is more frequent with macrosomic fetuses, some writers recommend routine Caesarean section for the delivery of fetuses greater than or equal to 4,500 g. The purpose of this study was to evaluate the appropriateness of this recommendation. A retrospective review was undertaken to determine how many fetuses born in our hospital weighing greater than or equal to 4,500 g died or were permanently damaged as a consequence of mechanical difficulties at delivery. During a 10-year period, 590 (75%) of 786 cephalic babies weighing greater than or equal to 4,500 g and alive at the start of labour were born vaginally. No baby died or was permanently damaged as a consequence of mechanical difficulties at delivery. Routine Caesarean section for macrosomic fetuses to prevent death or damage from difficult delivery is not warranted by our results.

Antecedents of macrosomia

Antecedents of high birthweight (macrosomia) were studied using the state birth certificates of White singleton infants born in three large metropolitan counties of Washington State from 1984 to 1986. Cases consisted of 2082 live-born macrosomic infants, defined by a birthweight of over 4.5 kg. A random sample of 4440 live births with birthweights of 2.5-4.0 kg was selected as a comparison group. Estimates for the independent risks associated with gestational and established diabetes, male sex, parity, duration of gestation, maternal smoking during pregnancy, maternal age, and median income of maternal residential area were obtained and combined in a single logistic model. Maternal smoking was associated with a decreased risk of macrosomia (OR 0.4, 95% CI 0.3-0.5). Established diabetes (OR 6.4, 95% CI 2.7-15.4), gestational diabetes (OR 3.2, 95% CI 2.1-5.1) and male sex of the infant (OR 2.4, 95% CI 2.2-2.7) were associated with an increased risk. Increasing parity was related to an increasing risk from para one (OR 1.4, 95% 1.2-1.6) to para six and greater (OR 3.3, 95% CI 1.5-7.4). Increasing duration of gestation was associated with an increasing risk from 33-36 weeks (OR 0.8, 95% CI 0.5-1.2) to 43-45 weeks (OR 3.3, 95% CI 2.5-4.2). Maternal age, median income of maternal area of residence, and maternal marital status were not significantly associated with macrosomia.