DOI 10.1515/jpm-2013-0256      J. Perinat. Med. 2014; 42(4): 449–455

Hyun-Joo Ko and Jong Kwan Jun*

Clinical factors associated with failed trials of labor in late preterm and term twin pregnancies Abstract Objective: To evaluate the perinatal outcomes and clinical factors of unsuccessful trials of labor (TOLs) in late preterm and term twin pregnancies. Methods: We enrolled 896 consecutive twin pregnancies delivered between 1999 and 2012 in a single center, which met the following inclusion criteria: a vertex first twin, live twins, and attempted TOLs after 34 weeks. Obstetric characteristics and perinatal outcomes were compared between vaginal delivery and cesarean delivery groups. Results: Successful TOLs were carried out in 81% (726/896). Failed TOLs occurred in 15% (37/247) of late preterm twins and 20% (133/649) of term twins. Comparisons of neonatal outcomes between the groups showed no significant differences in NICU admission, ventilator use, and composite morbidity. On univariable analysis, nulliparity, preeclampsia, induced labor, excessive weight gain, and intertwin weight discordance of  > 30% showed significant associations with failed TOLs. Multivariable analyses revealed nulliparity (adjusted odds ratio 9.89, 95% confidence interval 4.64–21.1) and preeclampsia (adjusted odds ratio 2.17, 95% confidence interval 1.30– 3.63) as significantly associated with failed TOLs. Conclusion: In late preterm and term twins, trials of labor can be performed successfully without a significant increase in adverse neonatal outcomes. Nulliparity and preeclampsia are clinical factors associated with failed TOLs in twin pregnancies. Keywords: Cesarean section; delivery; multiple pregnancy; neonatal outcome; perinatal outcome; trial of labor; twin pregnancy; twins. *Corresponding author: Jong Kwan Jun, MD, PhD, Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul National University Hospital, 101, Daehak-ro, Jongno-gu, Seoul 110-744, Korea, Tel.: +82-2-2072-3744, Fax: +82-2-762-3599, E-mail: [email protected] Hyun-Joo Ko: Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea

Introduction The rate of twin births has steadily increased in accordance with the increase in assisted reproductive technologies and more advanced childbearing age of women [6, 11, 21]. Although twin births account for approximately 3% of newborn births in many countries, it comprises 17% of preterm births, which have higher rates of perinatal morbidity and mortality [6, 11, 20, 21]. Twin pregnancy has its own unique characteristics of fetal growth based on the nature of plurality and its own risk affected by chorionicity, such as twin-to-twin transfusion syndrome or malformation from twinning. Moreover, there are concerns over increased risk during labor and delivery [15, 32]. Therefore, a number of studies have been performed to establish antenatal and intrapartum management strategies in order to improve maternal and perinatal outcomes in twin pregnancies [16, 19]. In planning the mode of delivery in twin pregnancies, a trial of labor (TOL) can be challenging in modern obstetrics due to the possible complications during labor and in the delivery of the second twin, as well as inexperience of obstetricians resulting in disqualification of breech extraction [4]. Although a planned cesarean section is considered protective against unpredictable adverse events during labor, it is not yet proven, with current evidence that planned cesarean delivery is indeed beneficial for obstetric outcomes. Currently, The American Congress of Obstetricians and Gynecologists and the French College of Gynaecologists and Obstetricians opine that there is a lack of sufficient evidence to permit recommendations on a specific route of delivery over the other [3, 29]. In terms of perinatal outcomes, several studies have shown that planned cesarean delivery did not improve adverse outcomes and no differences between vaginal birth and planned cesarean delivery were observed [7, 10, 15, 22]. A recent study using decision analysis did not support a policy of mandatory cesarean delivery of twins at or after 34 weeks of gestation [30]. Clinical decisions regarding the mode of delivery, until now, have been made primarily based on fetal presentation. Precedent observational studies and meta-analysis revealed that vaginal delivery could be attempted in twin pregnancies with vertex-vertex

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450      Ko and Jun, Failed trials of labor in late preterm and term twin pregnancies presentation [17, 24]. However, the optimal mode of delivery in cases of non-vertex second twins remains controversial due to concerns over the compromised safety of the second twin [5, 10]. Nevertheless, the vaginal route remains an option for delivery of twin pregnancies with a vertex presentation of the first twin irrespective of the presentation of the second twin, as several studies have shown no clear benefit from planned cesarean deliveries in terms of neonatal outcomes [14, 22, 28, 30]. Until forthcoming results from a large international multicenter randomized clinical trial entitled “Twin Birth Study” support a specific mode of delivery, data drawn from detailed in-hospital studies of vaginal trials containing relevant clinical variables can be potentially informative. At present, there are only a few studies evaluating factors contributing to the failure of TOLs that led to emergent cesarean sections. One large prospective study demonstrated that multiparity and spontaneous conception predicted vaginal birth [7]. Another study reported that the risk of cesarean delivery was associated with birth weight discordance and prolonged inter-delivery interval deliveries [5, 31, 33]. Other authors have reported an association with failed TOLs, nonvertex presentation of second twins, maternal complications, and not intertwin birth weight discordance [25]. Information discerning high-risk situations for TOLs may allow more detailed strategies, thereby, reducing risk and providing an informed choice on the mode of delivery. Therefore, the objective of this study was to evaluate the perinatal outcomes in TOLs and ascertain the clinical factors associated with unsuccessful TOLs in late preterm and term twin pregnancies.

Materials and methods We performed a review of all consecutive twin pregnancies delivered after 24 weeks’ gestation from January 1999 through December 2012 at a tertiary academic teaching hospital. Approval to conduct this study was obtained from the institutional review board of our hospital. All outcome data of twin pregnancies were retrieved from the electronic medical records of our hospital. In our institution, physicians primarily recorded all data regarding medical history, sonographic examinations, and pregnancy outcomes, as well as creating a composite data of labor and delivery. In addition, dedicated nurses collected detailed information regarding all demographic data, medical and obstetrical history, pregnancy complications, and social history, and recorded them in the electronic medical records of our hospital at each admission. Out of 1925 twin pregnancies, we enrolled 896 twin pregnancies that met the following inclusion criteria: a vertex first twin, live twins, and attempted TOL after 34 weeks of gestation. We excluded twin pregnancies in which single fetal demise occurred and those affected by twin-to-twin transfusion syndrome. These twins were divided into two groups according to the mode of delivery, vaginal delivery (VD) vs. cesarean delivery (CD).

We examined maternal characteristics and pregnancy outcomes as follows: age at delivery, parity, pre-pregnancy body mass index (BMI), BMI at delivery, mode of conception including in vitro fertilization (IVF), maternal medical diseases, preeclampsia, gestational diabetes, and the type of labor onset such as induction by prostaglandin or oxytocin or spontaneous onset, and delivery indications. Preeclampsia and gestational diabetes were diagnosed using standard criteria [1, 2]. BMI (kg/m2) was calculated using the height and weight prior to pregnancy and at delivery respectively. BMIs were classified according to World Health Organization criteria (overweight and obese  > 25.0 kg/m2) and excessive weight gain during pregnancy was based on the 2009 Institute of Medicine (IOM) guidelines, taking into account pre-pregnancy BMI [9, 13]. As the IOM did not make recommendations for underweight women (BMI 

Clinical factors associated with failed trials of labor in late preterm and term twin pregnancies.

To evaluate the perinatal outcomes and clinical factors of unsuccessful trials of labor (TOLs) in late preterm and term twin pregnancies...
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