Objective
The purpose of this study was to determine whether planned vaginal delivery is associated with increased risk of perinatal death and morbidity in twin pregnancies that are complicated by a very low birthweight of the second twin.
Study Design
We conducted a retrospective cohort study of twin pregnancies in which the second twin’s birthweight was ≤1500 g. One hundred ninety-three twin gestations met the study criteria; patients were classified into 2 groups according to the planned mode of delivery: (1) cesarean delivery (n = 142) and (2) vaginal delivery (n = 51). In the vaginal delivery group, 21 pairs were in cephalic-cephalic presentation at the time of delivery; 28 pairs were cephalic-noncephalic, and 2 pairs were noncephalic-noncephalic. Composite adverse neonatal outcome was defined as the presence of neonatal death, respiratory distress syndrome, sepsis, necrotizing enterocolitis, or intraventricular hemorrhage grade 3-4.
Results
Trial of vaginal delivery was successful for both twins in 90.5% of cephalic-cephalic twins and 96.4% in cephalic-noncephalic twins. The rate of intraventricular hemorrhage was significantly higher in the vaginal delivery group (29.4% vs 8.5%, respectively; P = .013; adjusted odds ratio [OR], 3.65; 95% confidence interval [CI], 1.32–10.1). The increased risk of intraventricular hemorrhage in the vaginal delivery groups was evident in both twin A (17.6% vs 7.0%; P = .029) and twin B (15.7% vs 4.9%; P = .014); however, these differences were not significant after adjustment for possible confounders (twin A: adjusted OR, 1.79; 95% CI, 0.58–5.55; twin B: adjusted OR, 2.13; 95% CI, 0.63–7.25). In addition, subgroup analysis revealed that both cephalic-cephalic and cephalic-noncephalic twins who were delivered vaginally had increased risk for intraventricular hemorrhage. There were no significant differences between the cesarean and vaginal delivery groups in the rates of Apgar score <7 at 5 minutes, arterial cord pH <7.1, composite adverse neonatal outcome, and neonatal mortality rate. However, the rate of respiratory distress syndrome was significantly lower in the vaginal delivery group (66.7% vs 69%; P = .042; OR, 0.34; 95% CI, 0.12–0.96).
Conclusion
Vaginal delivery of very low birthweight twins is associated with an increased risk of intraventricular hemorrhage, regardless of presentation. Because of the small sample size and the retrospective cohort design, large prospective randomized studies are needed.
The rate of twin gestations has increased over the last 30 years, mainly because of the growing rate of pregnancies that have been achieved via assisted reproductive techniques. The rise in twin pregnancies accompanied by the higher risk of premature delivery, which characterizes such pregnancies, have led to a significant increase in the rate of delivery of very low birthweight (VLBW; <1500 g) twins.
The optimal method of delivery of twins is controversial; several studies have addressed this question. Although some retrospective population-based studies have reported that vaginal deliveries are associated with increased fetal risk, mainly for the second twin, other cohort studies, 2 metaanalyses and a small prospective randomized study have shown no difference in perinatal outcome between planned vaginal and planned cesarean deliveries. Barrett et al recently have reported on a large prospective randomized controlled trial, in which a total of 2804 twin pregnancies between 32 and 39 weeks gestation were assigned randomly to planned vaginal or planned cesarean delivery. In this study, planned vaginal delivery did not increase risk for neonatal morbidity or death.
However, the data in the literature on the optimal mode of delivery for severe premature or VLBW twins are limited. Despite the limited information available, some authors have advocated for cesarean deliveries in cases of a second twin in a nonvertex presentation and with an estimated weight of <1500-2000 g. This view largely relies on extrapolation of data from breech deliveries of singleton gestation.
Other investigators have shown adverse outcome in VLBW twins who undergo vaginal deliveries and proposed that cesarean delivery is the optimal route of delivery for all twins who are expected to have a birthweight <1500 g, regardless of presentation.
Decisions regarding mode of delivery in VLBW twins are based on very limited data. This is especially true for pregnancies with a VLBW second twin in a nonvertex presentation. Therefore, we aimed to evaluate the association between the mode of delivery and perinatal morbidity and death in twin pregnancies that are complicated by VLBW of the second twin.
Methods
All twin deliveries in a single tertiary care medical center from August 2004 to April 2011 were reviewed. Inclusion criteria included (1) twin gestation and (2) second twin birthweight of ≤1500 g. Exclusion criteria included (1) gestational age at delivery of <24 weeks, (2) fetal death of 1 or both twins before labor, and (3) major malformation diagnosed in 1 or both twins.
The standard of care in our medical center regarding twin delivery is to allow vaginal delivery of cephalic-cephalic and cephalic-noncephalic twins, regardless of their estimated weight or the gestational age, as long as the estimated weight of twin B is not significantly higher (≥20%) than twin A. The delivery is supervised by an experienced obstetrician under continuous fetal monitoring, and the preferred method for delivering the noncephalic second twin is total breech extraction with or without internal podalic version.
A total of 193 twin gestations met the study criteria. Patients were classified into 2 groups according to the planned mode of delivery: cesarean delivery (n = 142) and vaginal delivery (n = 51). In the vaginal delivery group, 21 pairs were cephalic-cephalic; 28 pairs were cephalic-noncephalic, and 2 pairs were noncephalic-noncephalic. The charts of all women and their infants were reviewed for the variables of interest. Maternal characteristics and their pregnancy outcomes were abstracted from the obstetric electronic charts. The following neonatal outcomes were examined: Apgar scores at 5 minutes, cord blood PH, death, birth trauma (spinal cord injury, skull fracture, fracture of a long bone, peripheral nerve injury, and subdural or intracerebral hemorrhage), respiratory distress syndrome (RDS), sepsis, necrotizing enterocolitis (NEC), and intraventricular hemorrhages (IVH). Composite adverse neonatal outcome was defined as the presence of neonatal death, RDS, sepsis, NEC, or IVH grade 3-4.
Because decisions regarding the planned mode of delivery are made per pregnancy for both twins, we chose to analyze our data as outcomes per pregnancy. Outcome measures were defined as outcomes for twin A, twin B, or any twin. Comparison of continuous variables between the 2 groups was conducted using Mann-Whitney U test or the Student t test, as appropriate. Chi-square test was used for comparison of categoric variables. Logistic regression analysis was used to examine the relationship between mode of delivery and neonatal outcome measures. Adjustment was conducted for gestational age at delivery, chorionicity, and antenatal steroid treatment because these factors have been shown to be associated significantly with perinatal death and neonatal morbidity and thus may have a confounding potential. The regression model was limited to 4 variables to account for the small sample size. However, we also used an alternate regression model that adjusted for maternal age, parity, and birthweight in addition to gestational age at delivery, chorionicity, and antenatal steroid treatment. This model was not used in subgroup analysis according to presentation because the subgroups were significantly smaller. Significance was accepted at a probability value of < .05. Statistical analyses were conducted with the IBM Statistical Package for the Social Sciences (IBM SPSS version 19; IBM Corporation Inc, Armonk, NY).
The study was approved by the local institutional review board.
Results
A total of 193 twin deliveries that were complicated with VLBW of the second twin were identified during the study period. Of them, 142 delivered by cesarean section without trial of vaginal delivery, and 51 underwent trial of delivery. The vaginal delivery group included 2 cases of noncephalic-noncephalic twin pregnancies that attempted vaginal delivery despite our consultation to have a cesarean delivery. The main indications for cesarean delivery were a noncephalic first twin (35.3%), intrauterine growth restriction (17.6%), maternal request (12.5%), suspected fetal distress (11%), and previous cesarean delivery (5.9%). Demographic and clinical characteristics of the patients are presented in Table 1 . The groups did not differ with regards to maternal age, parity, body mass index, rate of gestational diabetes mellitus, male/female ratio, and rate of exposure to antenatal steroids. However, the median gestational age at delivery was 31.4 weeks in the cesarean delivery group compared with 30.4 weeks of gestation in the vaginal delivery group ( P = .025). Despite the significant difference in gestational age at delivery, median birthweights of both twins were not significantly different between the 2 groups (twin A: cesarean delivery 1417.5 g vs vaginal delivery: 1335 g; P = .183; twin B: 1258 vs 1195 g; P = .654). The rate of monochorionic twins was significantly higher in the cesarean delivery group compared with the vaginal delivery group (33.8% vs 11.8%; P = .034). The monochorionic pregnancies in the cesarean group included 4 cases of monoamniotic pregnancies. The higher rate of monochorionic pregnancies was adjusted for in our regression model.
| Variable | Cesarean delivery (n = 142) | Vaginal delivery (n = 51) | P value a |
|---|---|---|---|
| Maternal age, y b | 31 (29–35) | 31 (27–34.5) | .281 |
| Body mass index, kg/m 2 | 26.2 (23.6–29.1) | 24.4 (21.8–27.8) | .121 |
| Parity ≥ 1, n (%) | 47 (33.1) | 13 (25.5) | .633 |
| Monochorionic, n (%) | 48 (33.8) | 6 (11.8) | .034 |
| Gestational diabetes mellitus, n (%) | 17 (12) | 8 (15.7) | .498 |
| Exposure to steroids, n (%) | 142 (100) | 49 (96.1) | .722 |
| Gestational age at delivery, wk b | 31.4 (29.4–33) | 30.4 (28–31.9) | .025 |
| Birthweight, g b | |||
| Twin A | 1417.5 (1135–1700) | 1335 (1042–1562) | .183 |
| Twin B | 1258 (997–1395) | 1195 (1007–1372) | .654 |
| Male/female ratio, n/N | |||
| Twin A | 71/71 | 26/25 | .904 |
| Twin B | 69/73 | 26/25 | .77 |
a Calculated with the Mann-Whitney U test or the chi-squared test
In 8 cases in the vaginal delivery group, labor was induced because of intrauterine growth restriction. Outcome in induced twin pregnancies was generally favorable (no cases of RDS, IVH, or death; 1 neonate with NEC), most likely because of the relatively advanced gestational age at delivery of these cases (median gestational age, 34.1 wk; interquartile range, 33.5–34.5).
Mode of delivery in the trial of vaginal delivery group is displayed in Table 2 . The rates of vaginal delivery of both twins were high for both the cephalic-cephalic twins and the cephalic-noncephalic (90.5% and 96.4%, respectively). Only 1 case (from the cephalic-cephalic subgroup) resulted in cesarean delivery of twin B after a vaginal delivery of twin A, and 2 cases (1 in each subgroup) ended in cesarean delivery of both twins. There were no cases of documented birth trauma in either group, and there were no cases of intrapartum death. Excluding the cases that culminated in a cesarean delivery, all second twins in cephalic-noncephalic twin pregnancies were delivered by total breech extraction.
| Variable | Cephalic-cephalic (n = 21), n (%) | Cephalic-noncephalic (n = 28), n (%) |
|---|---|---|
| Vaginal delivery for both twins | 19 (90.5) | 27 (96.4) |
| Cesarean delivery for both twins | 1 (4.8) | 1 (3.6) |
| Cesarean delivery for twin B after vaginal delivery for twin A | 1 (4.8) | 0 |
Table 3 compares the neonatal outcome between the 2 groups. The rate of low 5-minute Apgar score and low arterial cord pH (pH <7.1) were similar between the 2 groups. Similarly, there were no significant differences in the rates of mortality, composite adverse outcome, sepsis, NEC, or neonatal intensive-care unit admission.
| Variable | Cesarean delivery (n = 142), n (%) | Vaginal delivery (n = 51), n (%) | P value | Adjusted P value | Adjusted odds ratio (95% CI) | |
|---|---|---|---|---|---|---|
| Model 1 | Model 2 | |||||
| Any twin | ||||||
| 5-Min Apgar score <7 | 9 (6.3) | 2 (3.9) | .523 | .09 | 0.2 (0.03–1.29) | 0.26 (0.04–1.83) |
| Umbilical artery pH <7.1 a | 2/74 (2.7) | 0/31 (0) | .362 | .995 | NA b | NA b |
| Composite outcome | 107 (75.4) | 37 (72.5) | .693 | .076 | 0.4 (0.14–6.91) | 0.28 (0.09–0.88) |
| Death | 8 (5.6) | 4 (7.8) | .575 | .679 | 0.74 (0.18–3.08) | 1.29 (0.25–6.55) |
| Respiratory distress syndrome | 98 (69) | 34 (66.7) | .757 | .042 | 0.34 (0.12–0.96) | 0.25 (0.08–0.76) |
| Necrotizing enterocolitis | 7 (4.9) | 2 (3.9) | .77 | .809 | 0.82 (0.16–4.17) | 1.37 (0.23–8.28) |
| Sepsis | 18 (35.3) | 48 (33.8) | .847 | .385 | 0.71 (0.33–1.53) | 0.61 (0.26–1.47) |
| Intraventricular hemorrhage | 12 (8.5) | 15 (29.4) | < .001 | .013 | 3.65 (1.32–10.1) | 4.86 (1.54–15.34) |
| Intraventricular hemorrhage grade 3-4 | 3 (2.1) | 6 (11.8) | .005 | .281 | 2.56 (0.46–14.08) | 4.88 (0.51–47.1) |
| Neonatal intensive care unit admission | 129 (90.8) | 46 (90.2) | .891 | .751 | 0.78 (0.17–3.55) | 0.69 (0.14–3.46) |
| Twin A | ||||||
| 5-Min Apgar score <7 | 4 (2.8) | 0 | .226 | .997 | NA b | NA b |
| Umbilical artery pH <7.1 a | 2/91 (2.2) | 0/32 (0) | .398 | .997 | NA b | NA b |
| Composite outcome | 87 (61.3) | 31 (60.8) | .952 | .116 | 0.49 (0.2–1.19) | 0.34 (0.13–0.9) |
| Death | 3 (2.1) | 3 (5.9) | .183 | .716 | 0.66 (0.07–5.99) | 0.86 (0.08–9.75) |
| Respiratory distress syndrome | 83 (58.5) | 29 (56.9) | .844 | .08 | 0.46 (0.19–1.1) | 0.34 (0.13–0.88) |
| Necrotizing enterocolitis | 2 (1.4) | 1 (2.0) | .784 | .819 | 1.33 (0.11–15.87) | 4.14 (0.17–102.4) |
| Sepsis | 21 (14.8) | 11 (21.6) | .264 | .871 | 0.92 (0.35–2.43) | 0.68 (0.23–2) |
| Intraventricular hemorrhage | 10 (7.0) | 9 (17.6) | .029 | .311 | 1.79 (0.58–5.55) | 2.16 (0.6–7.82) |
| Intraventricular grade 3-4 | 2 (1.4) | 4 (7.8) | .023 | .321 | 2.66 (0.38–18.52) | 3.47 (0.34–35.7) |
| Neonatal intensive care unit admission | 111 (78.2) | 42 (82.4) | .527 | .882 | 0.9 (0.22–3.56) | 0.59 (0.13–2.74) |
| Twin B | ||||||
| 5-Min Apgar score <7 | 6 (4.3) | 2 (3.9) | .919 | .152 | 1.06 (0.46–2.44) | 0.22 (0.02–2.43) |
| Umbilical artery pH <7.1 a | 1/88 (1.1) | 0/37 (0) | .515 | .996 | NA b | NA b |
| Composite outcome | 94 (73.4) | 34 (66.7) | .951 | .115 | 0.45 (0.17–1.21) | 0.38 (0.13–1.1) |
| Death | 6 (4.2) | 4 (7.8) | .317 | .972 | 1.03 (0.23–4.57) | 5.24 (0.26–105.3) |
| Respiratory distress syndrome | 79 (55.6) | 32 (62.7) | .378 | .499 | 0.73 (0.29–1.84) | 0.41 (0.14–1.19) |
| Necrotizing enterocolitis | 7 (4.9) | 1 (2.0) | .362 | .389 | 0.39 (0.05–3.32) | 0.67 (0.07–6.5) |
| Sepsis | 37 (26.1) | 12 (23.5) | .722 | .241 | 0.61 (0.27–1.39) | 0.76 (0.3–1.93) |
| Intraventricular hemorrhage | 7 (4.9) | 8 (15.7) | .014 | .224 | 2.13 (0.63–7.25) | 4.47 (0.99–20.1) |
| Intraventricular hemorrhage grade 3-4 | 2 (1.4) | 3 (5.9) | .084 | .948 | 0.92 (0.08–10.53) | 1.06 (0.04–27.1) |
| Neonatal intensive care unit admission | 124 (87.3) | 45 (88.2) | .866 | .809 | 0.85 (0.23–3.07) | 0.82 (0.22–3.1) |
a Umbilical artery pH was not available for all cases; the effective denominator is noted for each group
b Odds ratios were not calculated for cases with extremely high probability values (>.99).
IVH was significantly more common in the vaginal delivery group (29.4% vs 8.5%; P < .001) with an adjusted odds ratio (OR) of 3.65 (95% confidence interval [CI], 1.32–10.1). The rate of grade 3-4 IVH for any twin was also higher in the vaginal delivery group (11.8% vs 2.1%), however, statistical significance was lost after adjustment for confounders (adjusted OR, 2.56; 95% CI, 0.46–14.08). The rate of RDS, although not considerably different between the groups, appeared to be significantly lower in the vaginal delivery group compared with the cesarean delivery group after adjustment for confounders (66.7% vs 69%; P = .042; OR, 0.34; 95% CI, 0.12–0.96). When the regression model was altered to include more confounders, which included birthweight, maternal age, and parity (regression model 2), the only differences that were noted in our results were that the risk for composite outcome was significantly lower in the vaginal delivery group in any twin (OR, 0.28; 95% CI, 0.09–0.88) and in twin A (OR, 0.34; 95% CI, 0.13–0.9); that the risk for RDS in twin A was significantly lower in the vaginal delivery group (OR, 0.34; 95% CI, 0.13–0.88).
Because the presentation of the fetuses in twin pregnancies is pivotal in decision-making regarding mode of delivery and because the main clinical controversy is regarding delivery of cephalic-noncephalic twin pregnancies, we conducted a subanalysis according to the presentation of the twins in the vaginal delivery group (either cephalic-cephalic or cephalic-noncephalic; Table 4 ). A significantly increased risk for IVH was demonstrated in the vaginal delivery group compared with the cesarean delivery group, both for the cephalic-cephalic twins (33.3% vs 8.5%; P = .022; OR, 4.35; 95% CI, 1.24–15.38) and the cephalic-noncephalic twins (28.6% vs 8.5%; P = .025; OR, 4.88; 95% CI, 1.22–19.23). However, IVH grade 3-4 seemed to be more common only among the cephalic-noncephalic subgroup (17.9% vs 2.1%, respectively; P < .001), although this difference did not reach statistical significance after adjustment (OR, 6.58; 95% CI, 0.96–45.45). A decreased risk for RDS in the vaginal delivery group was significant after adjustment only in the cephalic-noncephalic subgroup (60.7% vs 69%; P = .041; OR, 0.27; 95% CI, 0.08–0.95). There were no significant differences compared with the cesarean delivery group in all other outcome measures (NEC, sepsis, neonatal intensive care unit admission, low 5-minute Apgar score, and low arterial pH) for either cephalic-cephalic twins or cephalic-noncephalic twins (data not shown).
| Variable | Cesarean delivery (n = 142), n (%) | Vaginal delivery cephalic-cephalic only (n = 21), n (%) | P value | Adjusted P value | Adjusted odds ratio (95% confidence interval) |
|---|---|---|---|---|---|
| Composite outcome | 107 (75.4) | 16 (76.2) | .934 | .343 | 0.46 (0.09–2.3) |
| Death | 8 (5.6) | 1 (4.8) | .87 | .625 | 0.58 (0.06–5.18) |
| Respiratory distress syndrome | 98 (69) | 15 (71.4) | .823 | .251 | 0.4 (0.09–1.9) |
| Intraventricular hemorrhage | 12 (8.5) | 7 (33.3) | .001 | .022 | 4.35 (1.24–15.38) |
| Intraventricular hemorrhage grade 3-4 | 3 (2.1) | 1 (4.8) | .464 | .79 | 1.5 (0.07–30.3) |
| Vaginal delivery cephalic-noncephalic only (n = 28) | |||||
| Composite outcome | 107 (75.4) | 19 (67.9) | .408 | .072 | 0.32 (0.09–1.11) |
| Death | 8 (5.6) | 2 (7.1) | .756 | .744 | 0.74 (0.12–4.63) |
| Respiratory distress syndrome | 98 (69) | 17 (60.7) | .391 | .041 | 0.27 (0.08–0.95) |
| Intraventricular hemorrhage | 12 (8.5) | 8 (28.6) | .003 | .025 | 4.88 (1.22–19.23) |
| Intraventricular hemorrhage grade 3-4 | 3 (2.1) | 5 (17.9) | < .001 | .055 | 6.58 (0.96–45.45) |
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