Objective: We aimed to compare the perinatal outcomes in late preterm spontaneous and indicated birth neonates. Methods: We studied 289 late preterm births, classified as either aspontaneous late preterm birth (sLPTB) group (preterm labor with intact membranes and preterm premature rupture of membranes) or an indicated late preterm birth (iLPTB) group (hypertensive disorder in pregnancy, placental causes, and maternal diseases), according to the delivery indication. We then compared the maternal and neonatal characteristics and perinatal outcomes, including the Apgar score, admission to the neonatal intensive care unit (NICU) or special care nursery (SCN), duration of NICU stay, and the rate of composite morbidity (antibiotic use, hypoglycemia, hypocalcemia, hyperbilirubinemia requiring phototherapy, respiratory support, and respiratory distress syndrome). Results: A total of 198 neonates were in the sLPTB group and 91 were in the iLPTB group. In spite of greater gestational age at the time of delivery in the iLPTB group, the mean birth weight was lower than that in the sLPTB group. Additionally, the iLPTB group showed lower Apgar scores, and higher rates of NICU or SCN admission, respiratory support, and hypoglycemia, but there was no difference in the rate of composite morbidity between the two groups. Conclusion: iLPTB neonates had lower birth weights despite greater gestational age than those in the sLPTB group, but there was no difference in the rate of composite morbidity between the two groups.
Late preterm births are defined as births at a gestational age between 34 weeks and 36 weeks, 6 days, and comprise nearly 74% of all preterm deliveries and approximately 8% of total deliveries [
This was a retrospective study of singleton late preterm births between January 2011 and December 2014 from our third-party referral center. We identified patients and collected clinical information from electronic medical records. We included late preterm births that were delivered between a gestational age of 340/7 and 366/7. We excluded multiple pregnancies, major structural anomalies (especially congenital heart anomalies), chromosomal anomalies, and stillbirths.
The spontaneous late preterm birth (sLPTB) group included preterm labor with intact membranes (PTL) and preterm premature rupture of membranes (PPROM); the indicated late preterm birth (iLPTB) group included hypertensive disorders such as gestational hypertension, preeclampsia and superimposed preeclampsia, placental causes (placental abruption, placental previa), fetal causes (intrauterine growth restriction, oligohydramnios, fetal distress), and maternal medical diseases, including cardiopulmonary or rheumatic diseases. We classified our study subjects into spontaneous and indicated preterm birth groups according to the direct reason for preterm delivery. A combination of PTL and PPROM cases were categorized by preceding events. We assessed maternal and neonatal characteristics including age, parity, gestational age at delivery, mode of delivery, birth weight, and gender. Additionally, we reviewed the Apgar score at 1 and 5 minutes after each birth, admission to the neonatal intensive care unit (NICU) or special care nursery (SCN), duration of NICU stay, and the rate of composite morbidity. Composite morbidity is defined as having more than one of the following: antibiotic use, hypoglycemia, hypocalcemia, hyperbilirubinemia requiring phototherapy, respiratory support, and respiratory distress syndrome (RDS). Criteria for NICU or SCN admission were as follows: gestational ageless than 35 weeks, birth weight less than 2.3 kg, or need for close observation by a neonatologist. The indications for antibiotic use were as follows: cases of PPROM, maternal fever, or suspicion of perinatal acquired infection. After confirmation of a negative culture test, antibiotics were stopped. Hypoglycemia was defined as plasma glucose less than 40 mg/dL, and hypocalcemia as an ionized calcium concentration of less than 4 mg/dL. Respiratory support was defined as the use of a mechanical ventilator or continuous positive airway pressure (CPAP). RDS was defined as the presence of diagnostic radiographic chest findings, plus one or more clinical signs of respiratory distress, including respiratory grunting, retracting, and increased oxygen requirement (fraction of inspired oxygen greater than 0.4), or the administration of exogenous pulmonary surfactant.
We then compared maternal and neonatal characteristics and perinatal outcomes in the two groups. This study used Pearson’s chi-squared (χ2) test for categorical variables and Student’s t-test for continuous variables. Statistical analysis was performed using SPSS software, version 19.0 (SPSS Inc., Chicago, IL, USA). This study was approved by the institutional review board (IRB) of Kyungpook National University Hospital and Kyungpook National University School of Medicine, South Korea (IRB No. 2016-04- 005).
Among 509 singleton preterm births during the study period, 65.6% (334 of 509) were late preterm births. We excluded 43 cases with major fetal anomalies, which could affect perinatal outcomes, and two stillbirths. Finally, we included 289 singleton late preterm births.
Among the 289 neonates in this study, 198 (68.5%) were in the spontaneous preterm birth group, and 91 (31.5%) were in the indicated group. Indications for late preterm births are shown in
There were several differences in maternal and neonatal baseline characteristics (
The perinatal outcomes in both groups are shown in
Spontaneous (n = 198) | Indicated (n = 91) | P value | |
---|---|---|---|
Maternal characteristics | |||
Age (year)* | 31.97 ± 4.40 | 33.48 ± 4.03 | 0.006 |
GAD (week)* | 35.2 ± 0.8 | 35.6 ± 0.8 | <0.001 |
GAD (weeks) | |||
34 weeks | 71 (35.9) | 16 (17.6) | <0.001 |
35 weeks | 76 (38.4) | 27 (29.7) | |
36 weeks | 51 (25.8) | 48 (52.7) | |
Nulliparity (%) | 109 (55.1) | 50 (54.9) | 0.987 |
Diabetes (%) | 19 (9.6) | 10 (11.0) | 0.714 |
Delivery mode | |||
Spontaneous vaginal delivery (%) | 102 (51.5) | 10 (11.0) | <0.001 |
Vacuum delivery (%) | 10 (5.1) | 0 (0) | |
Cesarean section (%) | 86 (43.4) | 81 (89.0) | |
Neonatal characteristics | |||
Birth weight (kg)* | 2.46 ± 0.35 | 2.26 ± 0.47 | <0.001 |
Male (%) | 116 (58.6) | 43 (47.3) | 0.072 |
GAD: gestational age at delivery; *mean ± standard deviation.
difference in NICU admission rates for neonates who reached 36 complete weeks of gestation (41.2% vs. 75.0%, p < 0.001). However, there was no statistically significant difference in the duration of NICU stay (11 days vs. 12 days, p = 0.271).
Spontaneous (n = 198) | Indicated (N = 91) | P value | |
---|---|---|---|
Perinatal morbidity | |||
Apgar score below 4 at 1 min (%) | 4 (2.0) | 9 (10.0) | 0.003 |
Apgar score below 7 at 5 min (%) | 3 (1.5) | 6 (6.7) | 0.020 |
Admission to NICU or SCN (%) | 139 (70.0) | 74 (81.3) | 0.046 |
34 weeks | 67 (94.4) | 15 (93.8) | 0.924 |
35 weeks | 51 (67.1) | 23 (85.2) | 0.073 |
36 weeks | 21 (41.2) | 36 (75.0) | <0.001 |
Duration of NICU stay (day)* | 11 (2-56) | 12 (2-366) | 0.271 |
Composite morbidity | 104 (52.5) | 55 (60.4) | 0.209 |
Antibiotics (%) | 75 (37.9) | 28 (30.8) | 0.241 |
Hypoglycemia | 3 (1.5) | 9 (9.9) | 0.001 |
Hypocalcemia | 7 (3.5) | 2 (2.2) | 0.543 |
Phototherapy (%) | 73 (36.9) | 28 (30.8) | 0.312 |
Respiratory support (%) | 20 (10.1) | 17 (18.7) | 0.043 |
Ventilator | 14 (7.1) | 13 (14.3) | |
Nasal CPAP | 6 (3.0) | 4 (4.4) | |
Respiratory distress syndrome | 12 (6.1) | 10 (11.0) | 0.142 |
Perinatal mortality | |||
Neonatal death (%) | 0 (0.0) | 0 (0.0) | - |
NICU: neonatal intensive care unit; SCN: special care nursery; CPAP: continuous positive airway pressure.
Lastly, there was no difference in the rate of composite morbidity between the two groups (52.5% vs. 60.4%, p = 0.209). However, the rate of hypoglycemia was higher in the iLPTB group (1.5% vs. 9.9%, p < 0.001), with no significant difference in the rate of gestational diabetes mellitus (GDM). Even though there was no difference in the rate of RDS between the groups, the rate of respiratory support was higher in the iLPTB group (10.1% vs. 18.7%, p = 0.043).
Similar to the results of previous studies, we found that sLPTB accounted for about 70% of all late preterm births and iLPTB for the remaining 30% in our study group [
Kase et al. reported that medically-indicated preterm birthshada significantly higher rate of small for gestational age (SGA) infants compared to the spontaneous preterm birth group in chronic hypertensive women, but there was no difference in perinatal outcomes between the two groups [
There was no difference in the rate of RDS between the two groups, but the rate of respiratory support was significantly higher in the iLPTB group, and was also associated with a higher rate of cesarean section in our study. A large population-based study from Nova Scotia showed that late preterm infants born by cesarean section without labor have an increased risk of adverse perinatal outcomes, such as need for resuscitation, total parenteral nutrition, transient tachypnea, hypoglycemia, necrotizing enterocolitis, and RDS or apneic spells [
Metabolic morbidities, such as neonatal hypoglycemia, hypocalcemia, or hyperbilirubinemia requiring phototherapy, are more common in late preterm births compared to full term births [
There are several limitations in our study. We could not evaluate important composite morbidities, such as bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), intraventricular hemorrhage (IVH), and mortality rate, due to uncertainty of these diagnoses and the small study sample size. In addition, we evaluated the rate of antibiotic use rather than the rate of sepsis, because clinical symptoms, such as tachypnea or respiratory difficulty, induced the administration of antibiotics before culture test results.
In conclusion, there was no difference in composite morbidity between the spontaneous and indicated groups. However, indication for delivery in late preterm birth might influence several perinatal outcomes (NICU admission, hypoglycemia, and respiratory support); therefore, obstetrical providers should individualize the management of late preterm deliveries.
Chun, D., Yoo, E.H., Lee, J.Y., Kim, H.M., Kim, M.J., Seong, W.J. and Cha, H.-H. (2016) Comparison of Perinatal Outcomes in Late Preterm Spontaneous and Indicated Preterm Birth Neonates. Open Journal of Obstetrics and Gynecology, 6, 661-668. http://dx.doi.org/10.4236/ojog.2016.612083