TABLE I FF MF MM PTD 37 wks (%) 55.4 54.5 57.8* .......................................................................................................................................................................................... PTD 32 wks (%) 16.0 14.5 17.7* .......................................................................................................................................................................................... PTD 28 wks (%) 6.6 5.8 7.5* .......................................................................................................................................................................................... LBW (%) 47.5* 42.1 41.3 .......................................................................................................................................................................................... VLBW (%) 11.4 9.4 11.8* .......................................................................................................................................................................................... 0002-9378/$ – see front matter • doi:10.1016/j.ajog.2009.10.126 112 The impact of prior gestational age at preterm delivery on the effectiveness of 17 alpha-hydroxyprogesterone caproate (17OHPC) in clinical practice Victor Hugo Gonzalez Quintero 1 , Lesley de la Torre 1 , Niki Istwan 2 , Debbie Rhea 2 , Carmen Maria Tudela 1 , Enrique Vazquez-Vera 1 , Gary Stanziano 2 1 University of Miami, Maternal Fetal Medicine, Miami, Florida, 2 Alere Women’s & Children’s Health, Clinical Research, Atlanta, Georgia OBJECTIVE: To examine if 17OHPC effectiveness is dependent on the earliest gestational age (GA) at prior spontaneous preterm birth (SPTB) when administered in the clinical setting. STUDY DESIGN: Identiﬁed from a database of women enrolled for out- patient perinatal services were women with current singleton gesta- tion and 1 prior SPTB between 20-36.9 weeks. Excluded were women reporting usage of progestational agents other than 17OHPC. Data were divided into 3 groups according to the earliest GA of a prior SPTB (20-27.9, 28-33.9, and 34-36.9 weeks). We compared GA at delivery of the current pregnancy and incidence of recurrent SPTB between women enrolled into the outpatient 17OHPC administra- tion program (weekly injections of 250mg 17OHPC) and women re- ceiving other outpatient surveillance services without 17OHPC. RESULTS: A total of 4238 women were identiﬁed. 2978 (70.3%) re- ceived weekly prophylactic 17OHPC injections in the current preg- nancy. Rates of recurrent SPTB are presented in ﬁgure: earliest SPTB = 20-27.9w, p=0.025, OR 0.693 (0.503, 0.956), (59% power for ob- served difference); 28-33.9w, p0.001, OR 0.618 (0.484, 0.790), (96% power); 34-36.9w, p0.001, OR 0.652 (0.535, 0.794), (98% power). CONCLUSION: 17OHPC given to prevent recurrent SPTB is effective regardless of GA at earliest SPTB. 0002-9378/$ – see front matter • doi:10.1016/j.ajog.2009.10.127 113 IVF versus spontaneous twins: a comparison of perinatal outcomes at Georgetown University Hospital Dennis Amini 1 , Helain Landy 2 , Yesmean Wahdan 3 , John Pezzullo 2 , Joseph Collea 4 1 Georgetown University/Washington Hospital Center, Obstetrics and Gynecology, Bethesda, Maryland, 2 Georgetown University, Washington, District of Columbia, 3 Georgetown University, District of Columbia, 4 Georgetown University Hospital, Obstetrics and Gynecology, Washington, District of Columbia OBJECTIVE: Singleton pregnancies conceived through IVF/ICSI have been shown to have increased adverse perinatal outcomes. European and Canadian studies have compared IVF/ICSI with spontaneously conceived twin pregnancies; unlike their singleton counterparts, twin gestations had similar outcomes. We studied these two patient groups at Georgetown University Hospital (GUH) in Washington DC, and compared their outcomes. STUDY DESIGN: We reviewed prenatal and hospital records of dichori- onic twin pregnancies delivered at GUH from 2006-2009; pregnancies with selective or spontaneous embryo reduction were excluded from analysis. 257 IVF/ICSI twin pregnancies and 190 spontaneously con- ceived twin pregnancies were analyzed. Maternal information in- cluded age, race, smoking history, BMI, BMI category, gravidity, ges- tational age at delivery, mode of delivery, cesarean incision type (if applicable), and the development of: preeclampsia, gestational diabe- tes, intrauterine growth restriction, inter-twin discordance, preterm premature rupture of membranes, chorioamnionitis, and abruption. Neonatal data included gender, fetal death, admission to Neonatal Intensive Care, 5 minute APGAR, birth weight, and congenital mal- formations. RESULTS: Mean age of mothers of IVF/ICSI conceived twins (37.4 +/- 5.3 years) was signiﬁcantly older than mothers of natural twins (32.3 +/- 5.2 years) (p0.001). Racial comparisons were different (81% Caucasian /8% African American) for women with IVF/ICSI conceived twins compared to those with women with spontaneous twins (59% Caucasian/ 32% African American). A comparison of all other maternal/pregnancy characteristics, delivery outcomes, and neonatal ﬁndings failed to show statistically signiﬁcant differences. CONCLUSION: Our ﬁndings show that perinatal outcomes for twins conceived by IVF/ICSI were not signiﬁcantly different from twins conceived spontaneously. 0002-9378/$ – see front matter • doi:10.1016/j.ajog.2009.10.128 114 Changes in azithromycin pharmacokinetics during pregnancy: relevance for dosage selection Mitra Habibi 1 , Gloria Sarto 2 , James Fischer 1 , Sarah Kilpatrick 1 , Ruth Tuomala 3 , Janice Shier 4 , Keith Rodvold 1 , Lori Wollet 2 , Patricia Fischer 1 , Karen McCarthy 3 , Zan Daley 5 1 University of Illinois at Chicago, Chicago, Illinois, 2 University of Wisconsin-Madison, Madison, Wisconsin, 3 Harvard University, Boston, Massachusetts, 4 University of Tennessee-Memphis, Tennessee, 5 University of Michigan, Ann Arbor, Michigan OBJECTIVE: Dosage regimens for azithromycin use in pregnancy de- rive from studies in nonpregnant women and men. To conﬁrm the suitability of these doses for pregnant women, this study compared azithromycin plasma concentration and pharmacokinetic (PK) pro- ﬁles in pregnant and nonpregnant women. STUDY DESIGN: Plasma samples, 5 per patient, and clinical data were prospectively collected in pregnant, 12-40 weeks gestational age (GA), and nonpregnant women of child bearing potential receiving oral azithromycin for treatment of an infection. PK data from 12 healthy women in whom extensive plasma sampling occurred were also in- cluded. Plasma samples were analyzed for azithromycin by a validated assay. Population PK parameters were determined by nonlinear mixed effects modeling. Inﬂuence of demographic and clinical vari- ables was evaluated by stepwise addition of covariates into the ﬁnal population model. www.AJOG.org Clinical Obstetrics, Neonatology, Physiology-Endocrinology Poster Session I Supplement to DECEMBER 2009 American Journal of Obstetrics & Gynecology S57