Advanced maternal age and risk of antepartum and intrapartum stillbirth Hamisu M. Salihu 1–3 , Roneé E. Wilson 1 , Amina P. Alio 4 and Russell S. Kirby 5 1 Department of Epidemiology and Biostatistics, and 2 Department of Obstetrics and Gynecology, University of South Florida, Tampa, Florida and, 3 Department of Family and Preventive Medicine, Emory University School of Medicine, Atlanta, Georgia and 4 Department of Community and Family Health, University of South Florida, Tampa, Florida, and 5 Department of Maternal and Child Health, University of Alabama at Birmingham, Birmingham, Alabama, USA Abstract Aim: We sought to assess the risk of antepartum and intrapartum stillbirth subtypes among women of advanced age. Methods: This is a retrospective cohort study using the Missouri maternally linked data containing births from 1978 to 1997. We examined the impact of maternal age on total, antepartum and intrapartum stillbirth across five maternal age group quintiles (20–24, 25–29, 30–34, 35–39 and 40) using mothers aged 20–24 years as the referent category. By means of the Cox proportional hazards regression models we obtained adjusted hazards ratios that quantified the magnitude of association between maternal age and the stillbirth subtypes. Results: The rates of antepartum and intrapartum stillbirth were greatest for older mothers (9.3/1000 and 1.2/1000 respectively) and lowest for gravidas aged 25–29 years (3.6/1000 and 0.8/1000 respectively). After adjusting for potentially confounding characteristics, older mothers still remained at greatest risk for antepar- tum and intrapartum stillbirth (adjusted hazards ratio = 3.6, 95% confidence interval = 2.9–4.4; and adjusted hazards ratio = 2.7, 95% confidence interval = 2.0–3.6 for antepartum and intrapartum stillbirth respectively). The risks for the two subtypes of stillbirth also increased with ascending maternal age in a dose-dependent pattern. Conclusions: As the demographic distribution of pregnant women persistently shifts to the right, care- providers will be increasingly confronted with elevated risks for adverse fetal outcomes among older mothers. Our results confirm this phenomenon and add new findings in relation to the elevated risk for intrapartum stillbirth among mothers advanced for age. Key words: advanced maternal age, antepartum, intrapartum, stillbirth. Introduction Childbearing among older mothers is on the rise. In the United States alone, the birth rate among gravidas aged 35 to 44 increased by 3–4% in a single year. 1 As women continue to delay childbearing, the heightened risk of fetal morbidity and mortality among this age group and beyond becomes more apparent. Previous research indicates mature gravidas are at increased risk of various adverse birth outcomes ranging from low birth weight to very low birth weight, preterm to very preterm, small size for gestational age and fetal mortal- ity or stillbirth. 2 Although a link between advanced maternal age and stillbirth has previously been documented, 3–5 little information is available on the timing of in utero fetal death. Reddy et al. conducted an analysis of more than 5 million singleton deliveries and determined that the peak risk period for stillbirth Received: September 11 2007. Accepted: December 28 2007. Reprint request to: Dr Hamisu Salihu, COPH, 13201 Bruce B. Downs Blvd., MDC 56, Tampa, FL 33612-3805, USA. Email: hamisu.salihu@gmail.com doi:10.1111/j.1447-0756.2008.00855.x J. Obstet. Gynaecol. Res. Vol. 34, No. 5: 843–850, October 2008 © 2008 The Authors 843 Journal compilation © 2008 Japan Society of Obstetrics and Gynecology