THE RELATIONSHIP OF INITIAL EMBRYO CROWN-RUMP LENGTH TO PREGNANCY OUTCOME AND ABORTUS KARYOTYPE BASED ON NEW GROWTH-CURVES FOR THE 2-31 MM EMBRYO

The objective of this study was to determine if measurement of initial crown - rump length (CRL) is helpful in predicting low birth weight, newborn length, spontaneous abortions, or abortus karyotype. We measur ed CRL prospectively in 837 consecutive singleton pregnancies at the t ime a heart rate was first detectable with transvaginal ultrasonograph y and compared these measurements to normal values for the 10th throug h 90th centiles determined from 227 transvaginal ultrasound measuremen ts in in-vitro fertilization and gamete intra-Fallopian transfer pregn ancies with known ovulation dates. The relationship of initial CRL to birth weight and length and to abortion and abortus karyotype was anal ysed after all pregnancies had delivered. Initial CRL measured after t he 28th post-ovulation day was predictive of subsequent abortion, but not of low birth weight or length. The abortion rate was 3.3% [95% con fidence interval (CI) 1.5%, 5.1%] when initial CRL greater than or equ al to 50th centile, compared to 19.4% (95% CI 15.4%, 23.4%) when <50th centile. Initial CRL, was <50th centile in 13 out of 14 trisomic and in eight out of 10 other karyotypically abnormal aborti. These results indicate that initial CRL measured after the 28th post-ovulation day may help to identify pregnancies at increased risk of abortion due to abnormal karyotypes.