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ORIGINAL RESEARCH |
From the 1Departments of Obstetrics and Gynecology, National Maternity Hospital and University College Dublin, Ireland.
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ABSTRACT |
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4,500 g). METHODS: Primiparas delivering a macrosomic infant during the years 1997–2000 were identified from a hospital computer database, and the obstetric outcome of a second delivery was analyzed up until June 2003. A control group (birth weight 3,000–3,500 g) served for comparison.
RESULTS: Among 13,020 first pregnancies, 301 (2.3%) were macrosomic. A similar proportion in the macrosomic group, 156 of 301 (52%), and control group, 171 of 300 (57%), returned for second delivery (P = .252). Compared with controls, first macrosomic deliveries were characterized by higher rates of operative delivery, anal sphincter injury, and shoulder dystocia. At second delivery, 32% of neonates in the macrosomic group and 0.3% in the control group weighed 4,500 g or more (P < .001). More prelabor cesareans were performed in the macrosomic group compared with controls (27 of 156, 17.3%, compared with 8 of 171, 4.7%; P < .001). Among 104 women in the macrosomic group who labored after first vaginal delivery, 99% (103 of 104) delivered vaginally again compared with 44% (11 of 25) who labored after primiparous cesarean delivery (P < .001), which compares with 97% (146 of 150) and 77% (10 of 13), respectively, in the control group.
CONCLUSION: Despite a one-third recurrence of macrosomia, first vaginal delivery of a macrosomic infant was associated with a high incidence of second vaginal delivery. Conversely, primiparous macrosomic cesarean delivery conveyed a high risk (56%) for repeat intrapartum cesarean whether macrosomia recurred or not.
LEVEL OF EVIDENCE: II-2
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METHODS |
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All women with pregestational or gestational diabetes mellitus (GDM) in a first or subsequent pregnancy were excluded from the study. Women with either historical risk factors (previous macrosomic infant [> 4,500 g], first-degree relative with diabetes mellitus, previous unexplained stillbirth, previous cardiac or sacral abnormality, prolonged steroid use, maternal age older than 40 years or maternal weight more than 100 kg), or risks unique to the current pregnancy (glycosuria, hydramnios, or suspected macrosomia) were identified as high risk for GDM. Screening for GDM was performed on this high-risk group using a 50-g oral glucose challenge test at 29 weeks gestation and progressing to formal 3-hour glucose tolerance testing (GTT) in that subset with an abnormal glucose challenge test (deemed positive if the 1-hour blood sugar level exceeded 8.3 mM or 150 mg/dL, a level selected to detect more than 95% of gestational diabetics screened in our hospital population). Diagnosis of GDM was made only by GTT using the criteria outlined by the National Diabetes Data Group.13 First pregnancies were screened selectively using the above criteria in the control and macrosomic cohorts and in all second and subsequent pregnancies when there was a history of macrosomia in a previous pregnancy.
First labors were managed according to a standard protocol of active management of labor,12 and as part of this protocol no attempt is made to estimate fetal weight routinely or to make a prelabor diagnosis of cephalopelvic disproportion, and suspected macrosomia was not deemed an indication for induction of labor or prelabor cesarean delivery. In subsequent pregnancies induction of labor was not recommended for a previous history of delivery of a macrosomic infant (as opposed to suspected macrosomia in a first pregnancy), although in some cases labor was induced at the discretion of the obstetrician or for maternal request.
In the absence of additional complications, our current practice is to offer a trial of vaginal delivery after 1 previous cesarean delivery but the final decision is individualized and prelabor cesarean is often determined by nonspecific factors such as previous experience in labor and the personnel preference of the patient and her obstetrician.14
Women in both control and macrosomic groups who sustained a third- or fourth-degree tear after first delivery were referred to a dedicated perineal clinic postpartum and were reassessed during their subsequent pregnancy; vaginal delivery was not contraindicated in the absence of significant alteration in fecal continence, normal anal manometry, and an endosonically defined anal sphincter defect of 1 quadrant or fewer.15 None of the women with criteria for a prelabor cesarean opted for vaginal delivery. However, the final decision regarding mode of delivery in women with a normal assessment was again individualized according to patient and obstetrician preference with some patients electing cesarean delivery.
Unpaired t test and Fisher exact test, 2-tailed, as appropriate, were used to analyze data, and a P value of < .05 was considered significant.
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RESULTS |
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A similar proportion in both the macrosomic and control groups returned for a second delivery at our institution within the period of analysis (52%, 156 of 301, compared with 57%, 171 of 300; P = .252), but there was no difference in the incidence of first delivery complications or interventions among those who did and did not return for second delivery (Table 1). Macrosomia recurred in 32% (50 of 156) of cases compared with an incidence of 0.3 % (1 of 300) among controls (P < .001).
At second delivery more prelabor cesareans were performed in the macrosomic group compared with the control group (27 of 156, 17.3%, compared with 8 of 171, 4.7%; P = .0004) (Fig. 1 and Table 2). Prelabor cesareans were performed in the macrosomic group because of previous anal sphincter injury in 5 of 27 (18%), malpresentation in 2 of 27 (7.4%), whereas the majority (20 of 27, 74%) of cases were elective repeat procedures. In the control group 7 of 8 prelabor cesareans were elective repeat procedures, and 1 was performed because of malpresentation; none of the 4 cases with a prior third- or fourth-degree tear met the criteria for prelabor cesarean delivery.
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Excluding prelabor cesarean deliveries, 83% (129 of 156) of women in the macrosomic group labored at second delivery compared with 95% (163 of 171) in the control group (P < .001). Among 104 of 129 women in the macrosomic group who labored after first vaginal delivery, 99% (103 of 104) delivered vaginally again (there was 1 intrapartum cesarean delivery for cord prolapse), compared with 44% (11 of 25) who labored after primiparous cesarean delivery (P < .001) (Figure 1) and with 97% (146 of 150) among controls with a prior vaginal delivery (P = .65) (Table 2). Among 25 of 129 in the macrosomic group who labored after primiparous cesarean delivery (1 after first prelabor cesarean for malpresentation who subsequently had a normal delivery of a macrosomic infant), the vaginal birth after cesarean (VBAC) rate was 44% (11 of 25) (Fig. 1), which compares with a VBAC rate of 77% (10 of 13) in the control group (P = .086). The incidence of macrosomia in those attempting VBAC (7/25; 28%) was similar whether successful (3/11; 27%) or not (4/14; 28%) and similar to the incidence of macrsosomia in second prelabor cesareans (9/27; 33%). The indications for intrapartum cesarean delivery for failed VBAC (14/25) were fetal distress in 3 cases, dystocia in 5 cases, failed induction of labor in 4 cases, pyrexia in labor in 1 case, and placental abruption in early labor in 1 case. Overall, the intrapartum cesarean rate in the macrosomic group was significantly higher than controls (15 of 129, 11.6%, compared with 7 of 163, 4.2%; P = .024), and the majority (14 of 15, 93%) were performed in women who labored after previous cesarean compared with 3 of 7 (43%) in the control group (Fig. 1 and Table 2).
Second labor was induced in 32.7 % (51 of 156) of women in the macrosomic group. The median gestation at induction was 41 weeks with 6.4% (10 of 156) of women having labor induced before 40 weeks. The most common indication for induction of labor was postmaturity 41.2% (21 of 51), with 21.6% (11 of 51) of women induced on the basis of a previous history of macrosomia, 13.7% (7 of 51) because of hypertension, and 7.8% (4 of 51) induced because of prelabor rupture of membranes. The remaining 8 women were induced for a variety of indications, including pains and reduced fetal movements. Of those women induced, 75% (37 of 51) achieved a spontaneous vaginal delivery, 12% (7 of 51) an instrumental delivery, and 12% (7 of 51) were delivered by cesarean; 43% (22 of 51) of those induced in the macrosomic group delivered another macrosomic infant.
In the macrosomic group, the distribution of second macrosomic infants by mode of delivery was similar: vaginal delivery 32.2% (37 of 115), intrapartum cesarean 28.6% (4 of 14) (combined—32%, 41 of 129), and prelabor elective cesarean 33% (9 of 27), P = .793. Only 1 woman in the control group delivered a second infant that was macrosomic. Second vaginal delivery was associated with anal sphincter injury in 1.7% (2 of 115) of the macrosomic group compared with 0.6% (1 of 156) of the control group. In the macrosomic group 3.5% (4 of 115) of deliveries were complicated by shoulder dystocia,4 with none among controls (Table 2). None of the infants developed a permanent brachial plexus injury.
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DISCUSSION |
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4,500 g) was associated with an increased incidence of cesarean delivery for dystocia, operative delivery, shoulder dystocia, and perineal trauma compared with a control group delivering a neonate weighing between 3,000 and 3,500 g. Just over 50% (156/301 and 171/300), of women in both the macrosomic and control groups returned for a second pregnancy within 6 years, but the distribution of obstetric outcomes—good and bad—was similar in those who did and did not return. The rate of recurrence of macrosomia in a second delivery was high (32%). Our institute does not have a policy of routine antenatal ultrasound estimation of fetal weight even if macrosomia is suspected. Antenatal ultrasonographic diagnosis of suspected macrosomia is associated with a significant increase in cesarean delivery rates even in nonmacrosomic neonates16 and is not associated with a significant reduction in shoulder dystocia or fetal injury,17 and because the majority of these cesareans are performed after failed induction, it is recommended that the onset of spontaneous labor is preferable.18,19
At second delivery the higher incidence of prelabor cesarean in the macrosomic group reflects the high primary cesarean rate, and in addition, almost one fifth were performed for altered fecal continence after prior obstetric anal sphincter injury. No prelabor procedure was performed in the control group for previous perineal trauma. In the macrosomic prelabor cesarean group the distribution of macrosomia (one third) was similar to those delivering vaginally, illustrating that mode of delivery was not routinely selected on the basis of suspected macrosomia.
The most important observation in this study is the high rate of second vaginal delivery after primiparous delivery of a macrosomic infant despite a one-third recurrence of macrosomia. This rate did not occur at the expense of an increased risk of perineal injury or shoulder dystocia and shows that women who have had a first delivery of a macrosomic infant can safely be counseled toward a vaginal delivery in the next pregnancy.
The rate of recurrence of macrosomia (32%) is a cause of concern in planned second vaginal delivery, predominantly because of the perceived risk of perineal trauma and shoulder dystocia. For this reason, women with a history of anal sphincter injury in a first pregnancy were carefully selected for trial of labor during the antenatal period by a detailed assessment of anal sphincter function in a dedicated perineal clinic, including continence assessment, anal manometry, and endoanal ultrasonography.15 Based on these assessments one half were referred for prelabor cesarean, and of those delivered vaginally, none sustained a second- or third-degree tear. The overall rate of anal sphincter injury after second vaginal delivery in the macrosomic group was 1.5%—twice the expected rate in multiparas (0.8%), but significantly less than the rate in primiparous macrosomic deliveries (7%) and less than the overall risk in primiparous delivery20 (2.9%). These data put this level of risk in perspective.
The second major concern about macrosomic vaginal delivery is occurrence of shoulder dystocia. It is very clear that an increasing birthweight is associated with increasing rates of shoulder dystocia.21,22 From our own data, only one third of neonates will be macrosomic at second delivery. The relative benefit of elective cesarean for suspected macrosomia remains controversial10,23,24 and one analysis suggests that because of the difficulty in accurately estimating antenatal fetal weight, the number of prelabor cesareans required to avert 1 case of permanent brachial plexus injury would make a policy of prophylactic cesarean delivery both clinically and financially prohibitive.24
The final concern is the safety of vaginal delivery after first cesarean, specifically the potential risk of uterine scar rupture. The rate of vaginal birth after cesarean in our macrosomic group was only 44%, and this may reflect a negative influence of the previous history on management of labor despite the fact that recurrence of macrosomia (28%) was lowest in this cohort. A number of studies report lowest success rates for VBAC when macrosomia is combined with no previous vaginal delivery and when the first cesarean was indicated for dystocia in labor; factors that applied to almost all our cases considered for trial of VBAC. An increased incidence of scar dehiscence was also reported,25,26 and unplanned cesarean delivery was associated with a higher infectious morbidity.27 On that basis institutions should individualize their approach to this important group with a previous cesarean delivery, and a recommendation for elective repeat cesarean would seem reasonable if macrosomia was suspected, despite the caveats expressed above regarding antenatal detection of macrosomia.
The results of this study provide information for counseling women during a pregnancy subsequent to a macrosomic primiparous delivery. The primary cesarean delivery rate is high, and prelabor repeat cesarean will be recommended for many reasons. In addition, one can anticipate a high rate of intrapartum cesarean after previous primiparous cesarean of a macrosomic infant. However, the very good results after first vaginal delivery of a macrosomic infant strongly support the case for a trial of vaginal delivery, with safe vaginal delivery anticipated in almost 100% of cases.
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Footnotes |
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Corresponding author: Dr. Michael E. Foley, Department of Obstetrics and Gynaecology, University College Dublin, National Maternity Hospital, Holles Street, Dublin 2, Ireland; e-mail: mfoley{at}nmh.ie.
doi:10.1097/01.AOG.0000203340.09961.0b
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REFERENCES |
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