• Early pregnancy;
  • growth restriction;
  • miscarriage;
  • ultrasound

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.