OBJECTIVES: To examine whether viable early pregnancies that subsequently end in miscarriage exhibit evidence of first-trimester growth restriction. DESIGN: Prospective cohort study. SETTING: Early pregnancy unit (EPU) of a teaching hospital. POPULATION: Women attending EPU between 5 and 10 weeks of gestation. METHODS: Women with spontaneously conceived intrauterine, viable singleton pregnancies with certain last menstrual period and regular cycles were included. The deviation between the observed and expected crown-rump length (CRL) for gestation was calculated and expressed as a z score. Pregnancies were followed up until the 11-14 week scan, and the deviation between those that remained viable and miscarried subsequently was calculated. MAIN OUTCOME MEASURES: Viability at 11-14 week scan. RESULTS: Over 6 months, 316 women met the inclusion criteria. Twenty-four (7.4%) women were excluded. Of the remaining 292, the pregnancy remained viable in 251 (86%) and 41 (14%) suffered a miscarriage. At the first transvaginal ultrasound, the z score of the mean measured CRL for pregnancies that remained viable was -0.82, SD 1.46, while in pregnancies that subsequently miscarried the z score was -2.42 and the CRL was significantly smaller, SD 1.31 (P < 0.0001). In the latter group, the initial CRL was below the expected mean for gestational age in all women, while in 61% (25/41), the CRL was at least 2 SDs below the expected mean. CONCLUSIONS: CRL was significantly smaller in pregnancies that subsequently ended in miscarriage. This suggests that early first-trimester growth restriction is associated with subsequent intrauterine death.