extensive evaluation, it may not be possible to determinea cause of fetal death. Such unexplained lossesare common, especially in third trimester stillbirth.There have been numerous attempts to catalogcauses of fetal death, typically greater than 20 weeksof gestation, using classification systems. None havebeen universally accepted, and all have advantagesand disadvantages. Further confusion arises from theuse of different definitions of fetal death amongsystems and the inclusion of neonatal deaths in somebut not all classification schemes. Popular classificationsschemes include the Aberdeen clinicopathologicclassification8 and the Wigglesworth classification9scheme that is probably most commonly used today.Recently, Gardosi and colleagues developed a newsystem that substantially decreased the proportion ofunexplained stillbirths compared with traditional classificationschemes.10 However, this system ascribed avery large proportion (43%) of deaths to fetal growthrestriction, which may be an association rather than acause of fetal death (see below). There is ongoingdialogue among investigators throughout the world toagree on a uniform system to facilitate comparison offetal death rates and research into causes and preventionof fetal death.It is important to distinguish between conditionsthat clearly and unequivocally cause fetal death andthose that are associated with the condition. Theselatter conditions are present in many cases of livebirths and do not always cause the unavoidable deathof the fetus. This distinction is not merely academic; ithas important implications for clinical practice andcounseling of couples with fetal death.RISK FACTORS AND CAUSESMaternal ConditionsDemographicsConsistent demographic factors for fetal death includerace, low socioeconomic status, inadequateprenatal care, less education, and advanced maternalage.11,12 African-American women have rates of fetaldeath that are more than twice the rate for whitemothers. In part, this may be due to secondary riskfactors such as socioeconomic status and a lack ofprenatal care. However, African Americans havehigher fetal death rates than whites even amongwomen receiving prenatal care.13 This may be due tohigher rates of medical and obstetric complications inAfrican Americans.13 It is unclear whether improveduse of obstetric care would reduce the fetal death ratein African-American women, but it seems likely.Maternal AgeFretts and colleagues demonstrated that increasingmaternal age after 35 years is associated with anincreased risk for fetal death.14 These findings havebeen confirmed in numerous studies, and the association

persists when adjusting for potential confoundingvariables such as genetic problems, birth defects,medical problems, and maternal weight. A largeinpatient-based study in the United States estimatedthe odds ratio for stillbirth to be 1.28 (95% confidenceinterval [CI], 1.24 –1.32) in women aged 35–39 yearsand 1.72 (95% CI, 1.6 –1.81) in women aged 40 yearsor older compared with 20–34-year-old women.15ObesityThe rate of fetal death also is increased in obesewomen. Numerous studies have shown a consistentdoubling in the risk for fetal death in cases of maternalobesity (body mass index of 30 or more).16 Increasedbody mass index increases the risk for several conditionsknown to increase the risk of stillbirth, such asdiabetes, hypertensive disorders including preeclampsia,socioeconomic status, and smoking. Nonetheless,obesity remains associated with fetal deathafter controlling for these confounders. The associationbetween obesity and fetal death is of particularconcern given the dramatic and persistent increase inthe rate of maternal obesity.Medical DisordersSeveral maternal medical disorders are associated withan increased risk for fetal death. It is debatable as towhether these conditions are causal or risk factorsbecause most affected women deliver liveborn infants.Perinatal outcome is influenced by obstetric managementand decreased morbidity, and mortality frommaternal diseases such as diabetes and hypertension areresponsible for much of the improvement in fetal deathrates over the past half century. It is estimated thatmaternal diseases play a role in 10% of fetal deaths.Despite improved care, women with diabetesmellitus (type 1 and 2) have a 2.5-fold increase in therisk for fetal death.17 Conversely, true gestationaldiabetes (type 2 diabetes may be first recognizedduring pregnancy) is not associated with an increasedrisk for fetal death. In part, fetal death in diabeticwomen is due to increased fetal anomalies and co