inclusion criteria. An elective cesarean section (CS) was performed in65 (9.9%) women. In the planned vaginal birth group N�593(90.1%), 488 (82.3%) women delivered both twins vaginally, 80(13.5%) had a CS during labor for both twins, in 25 (4.2%) a CS wasdone for the second twin. Perinatal mortality was 0 in the elective CSgroup, versus 1 (0.08%) in the planned vaginal birth group. Neonatalmorbidity was 116/658 pregnancies, or 16 children (16/130�12.3%)in the elective CS versus 100 (100/1316�7.6%) for the planned vagi-nal births (p�0.05).CONCLUSION: Our results do not support an elective caesarean sectionfor twin gestations � 32 weeks when twin A is presented in vertexposition.

161 Maternal sleep health and fetal outcomesSusan Walker1, Alison Fung2, Danielle Wilson3,Maree Barnes3, Mark Howard3, Helen Esdale4

1Mercy Hospital for Women, University Of Melbourne Department ofObstetrics and Gynaecology, Melbourne, Australia, 2Mercy Hospital forWomen, University of Melbourne, Dep’t of Obstetrics and Gyaecology,Melbourne, Australia, 3Austin Health, Institute of Breathing and Sleep,Melbourne, Australia, 4Mercy Hospital for Women, University of MelboureDepartment of Obstetrics and Gynaecology, Melbourne, AustraliaOBJECTIVE: There are little data on the fetal outcomes of polysom-mographoically confirmed obstructive sleep apnoea (OSA) in preg-nancy. Our hypothesis was that OSA may be associated with; (i) acutefetal compromise, as evidenced by fetal heart decelerations on contin-uous fetal cardiotocography during periods of maternal hypoxia, hy-percapnia and sympathetic activation. (ii) chronic fetal compromise,as evidenced by a fall in fetal growth trajectory on serial third trimesterultrasound examinations, and altered cord blood levels of fetal growthregulators.STUDY DESIGN: Preliminary questionnaires identified women as po-tential OSA cases and controls. The fetal growth trajectory across thethird trimester was determined by performing serial ultrasound ex-aminations, and a fall of �30% of the customised fetal weight centilefrom 32 weeks to birth was considered significant . At 37 weeks ges-tation, polysommography with synchronised fetal heart rate monitor-ing was performed, and cord blood collected at delivery.RESULTS: 36 women have completed the study, 10 of whom had con-firmed OSA. Acute Compromise: one case of an abnormal CTG oc-curred in a woman with OSA and a growth restricted fetus. There wereno other fetal heart rate abnormalities detected, despite moderateOSA associated with significant maternal oxygen desaturation.Chronic compromise: women with OSA were more likely to demon-strate an impaired growth trajectory during the third trimester thanwomen without OSA (33% vs 4%, p �0.05). In addition, insulingrowth factor-II (IGF-2) was significantly lower in the cord blood ofinfants whose mothers had OSA compared with BMI-matched con-trols (p�0.05).CONCLUSION: We have confirmed that OSA may be associated withacute and chronic fetal compromise. Given the established link be-tween obesity and stillbirth, it is intriguing to consider whether OSAmay be an important intermediary. That there is therapy for OSAavailable in the form of Continuous Positive Airway Pressure (CPAP),is particularly exciting, but further study with larger numbers isneeded to confirm these results.

162 The degree of obesity effect onlabor outcome following inductionShay Porat1, Cynthia Maxwell1, Mathew Sermer1, Dan Farine2

1Mount Sinai Hospital, Obstetrics and Gynecology, Toronto,ON, Canada, 2Mount Sinai Hospital, University of Toronto,Obstetrics and Gynecology, Toronto, ON, CanadaOBJECTIVE: The association between obesity and pregnancy relatedcomplications for both the mother and the fetus is well documented.The objective of this study was to investigate the impact of differentdegrees of obesity on the characteristics and outcome of labor induc-tion.STUDY DESIGN: The study population included all parturients who hadinduction of labor (IOL) of a term singleton pregnancy between 2003-2010 in a single tertiary center. Pregnancies with a diagnosed intra-uterine fetal demise, abnormal fetuses (malformations, IUGR) orprolonged SROM were excluded from analysis. The patients wereclustered according to WHO obesity classification. The associationbetween obesity and obstetrical outcomes of IOL was studied.RESULTS: The study population included 8183 patients. Clustering thepatients according to WHO obesity classes by BMI at the time ofdelivery (rather than by periconceptual BMI) showed the best corre-lation with a composite outcome of C/S, VBAC failure, repeated epi-dural, neonatal birthweight, 1 minute Apgar score and need for resus-citation. Univariate analysis is (summarized in table 1) demonstratedthat obesity is associated with lower height, smoking, GBS carriageand unfavorable cervix. Likewise, obesity was found to be a risk factorfor prostin/mechanical induction, need for scalp clip electrode, needfor repeat epidural anesthesia placement, prolonged 2nd stage, cesar-ean delivery, VBAC failure, higher neonatal birthweight, perineal lac-erations, lower 1 minute Apgar score and increased risk for neonatalresuscitation. A logistic regression analysis was performed for the out-come of cesarean delivery, and the following variables were found tobe significant independent predictors : nulliparity, dilatation on ad-mission, 2nd stage length, intra-partum fever, birthweight and deliv-ery BMI.CONCLUSION: Obesity was shown to be a significant contributor to un-desirable IOL outcomes. BMI at the time of delivery is a closer corre-late than periconceptual BMI to the studied outcomes, emphasizingthe importance of weight gain control during pregnancy.

Poster Session I Clinical Obstetrics, Medical-Surgical-Disease, Neonatology, Physiology-Endocrinology www.AJOG.org

S84 American Journal of Obstetrics & Gynecology Supplement to JANUARY 2012