K. Avgidou

Multicenter study of first-trimester screening for trisomy 21 in 75 821 pregnancies: results and estimation of the potential impact of individual risk-orientated two-stage first-trimester screening

To evaluate the performance of first‐trimester screening for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) and maternal serum free β‐human chorionic gonadotropin (β‐hCG) and pregnancy‐associated plasma protein‐A (PAPP‐A). In addition, the potential impact of a new individual risk‐orientated two‐stage approach to first‐trimester screening was examined.

First‐trimester biochemical markers of aneuploidy and the prediction of small‐for‐gestational age fetuses

To examine the clinical utility of the first‐trimester biochemical markers of aneuploidy in their ability to predict subsequent delivery of a small‐for‐gestational age (SGA) infant.

Cystic Hygromas, Nuchal Edema, and Nuchal Translucency at 11-14 Weeks of Gestation

OBJECTIVE: To estimate the incidence of septations in fetuses with increased nuchal translucency (NT) thickness, and to investigate the relationship between the length and thickness of the translucency and whether the length or septations provide useful information concerning the fetal karyotype in addition to that provided by the NT thickness alone. METHODS: We examined 386 fetuses with NT thickness equal to or above the 95th percentile for crown-rump length (CRL). A transverse suboccipitobregmatic section of the fetal head was taken to determine whether the sonolucency was septated, and a midsagittal longitudinal section was used to measure NT thickness, CRL, the longitudinal distance between the occiput and the lower end of the sonolucency toward the fetal sacrum (NT length) and the length between the occiput and the sacral tip (spinal length). Logistic regression analysis was used to investigate the effect on abnormal karyotype of CRL, NT thickness, and percentage of NT length to spinal length. RESULTS: Septations within the translucency were observed in all fetuses. The fetal karyotype was abnormal in 83 (21.5%) pregnancies, and multiple regression showed that the only significant independent predictor of abnormal karyotype was fetal NT thickness. CONCLUSION: Septations within the translucency can be seen in all fetuses, and therefore this feature cannot be used to distinguish between increased NT and cystic hygromas. The length of the translucency is related to its thickness and does not give useful information concerning the fetal karyotype in addition to that provided by the NT thickness alone. LEVEL OF EVIDENCE: II-2

Dilemmas in the management of twins discordant for anencephaly diagnosed at 11 + 0 to 13 + 6 weeks of gestation

To help develop an evidence‐based approach to the best management of twin pregnancies discordant for anencephaly.

OC24: First‐trimester intrauterine growth restriction in fetuses with chromosomal abnormalities

Objective: To examine the growth deficit in the first trimester in fetuses with chromosomal abnormalities. Methods: We performed a retrospective study examining crown–rump length (CRL) in all live fetuses examined between 11 and 13 + 6 weeks of gestation that were subsequently found to be affected with chromosomal abnormalities and who fulfilled the following entry criteria: (i) known last menstrual period (LMP); (ii) regular menstrual cycle between 26 and 30 days; (ii) no oral contraceptive use or pregnancy for three menstrual cycles prior to the LMP. The median CRL for gestational age was calculated for each fetus, and the actual CRL was subtracted from this. This deviation (delta value) was expressed in days of gestation. The median growth deficit (and interquartile range, IQR) for each of the chromosomal abnormalities was then calculated. Results: There were 2020 chromosomally abnormal fetuses included in the study. The median growth deficit was greatest for fetuses affected with triploidy (n = 79, median growth deficit 8 (IQR 4 to 11) days) and trisomy 18 (n = 399, deficit 6 (3 to 8) days). The deficit was less for those with trisomy 13 (n = 165, deficit 2 (0 to 6) days), while there was no significant growth deficit in fetuses with trisomy 21 (n = 1141, deficit 0 (−3 to 2) days), Turner syndrome (n = 179, deficit 2 (−1 to 5) days) or sex chromosome abnormalities (n = 57, deficit −1 (−2 to 1) days). Discussion: Fetuses with triploidy, trisomy 18 and trisomy 13 exhibit early intrauterine growth restriction in the first trimester. No significant growth restriction is seen in fetuses affected with trisomy 21, Turner syndrome or other sex chromosome abnormalities.

OC3.04: Short‐term outcome of trichorionic triplet pregnancies at 10–14 weeks: embryo reduction compared to expectant management

followed by spina bifida (17%), ventriculomegaly (13%), hydrocephaly (11%), agenesis of corpus callosum (7%), Dandy–Walker malformation (7%), micro-/macrocephaly (5%), anencephaly (3%) and holoprosencephaly (2%). A total of 31% of pregnancies were terminated, and 5% ended in late spontaneous abortion or intrauterine death. A total of 64% of pregnancies (126/198) resulted in live birth. 8 children died postnatally, 118 are alive. Long-term followup (6 months to 9 years) was available in 77 infants. Psychomotor development was normal or slightly disabled for 56% of children, mostly with mild or isolated lesions. Conclusions: The study covers a large study group and describes a long follow-up period. The prognosis for surviving children depends on their specific anomaly. Overcoming the limitations of scant and controversial data leads to a better counselling of the parents about the likely outcome.

OC38.03: One stop clinic for assessment of risk (OSCAR) for trisomy 21 in singleton pregnancies at 11 to 13 + 6 weeks of gestation

Objective: To evaluate the performance of first-trimester screening for trisomy 21 using maternal age, fetal nuchal translucency (NT) and maternal serum free s-hCG and PAPP-A at 11 to 13 + 6 weeks. Methods: All women attending between 11 to 13 + 6 weeks of gestation were offered screening for trisomy 21. Assessment of NT was performed by appropriately trained sonographers (Fetal Medicine Foundation Certificate of competence), and maternal serum s-hCG and PAPP-A was measured using the Kryptor analyser. Patients were counselled with regards to their combined estimated risk and the available options for the management of the pregnancy. Data on pregnancy outcome were obtained from the cytogenetics laboratory, and by letters and telephone calls to the patients, their general practitioners or the maternity units in which they delivered. Detection rates and false positive rates were calculated for use of maternal age, maternal age and NT, and maternal age, fetal NT and maternal biochemistry. Results: Screening for trisomy 21 was carried out in 31 904 singleton pregnancies and pregnancy outcome was obtained in 30 564 (95.8%) cases. There were 330 pregnancies affected with a chromosomal abnormality, including 196 cases of trisomy 21. Of these, in 185 cases the diagnosis was made prenatally (178 in the screen positive and seven in the screen negative pregnancies) and 11 where the diagnosis was made postnatally in live births (five in the screen positive pregnancies, in which the parents chose to avoid invasive testing, and six in the screen negative pregnancies). The estimated risk for trisomy 21 was 1 in 300 or greater in 7.5% of the normal pregnancies, in 93.4% of those with trisomy 21 and in 88.8% of those with other chromosomal defects. Conclusion: Currently, the most effective method of screening for trisomy 21 is by a combination of maternal age, fetal NT and maternal serum free s-hCG and PAPP-A at 11 to 13 + 6 weeks.

P03.06: First‐trimester sonographic features of trisomy 13

Background: The rapid aneuploidy detection with quantitative fluorescent polymerase chain reaction (QF-PCR) allows reliable prenatal diagnosis of trisomies 21, 18 and 13. Discussion raised, if single QF-PCR could be an alternative to traditional cytogenetic karyotyping for certain referral categories. Objective: To evaluate an indication-based classification for the risk of missing clinical relevant chromosomal disorders by QF-PCR. Methods: From October 1999 to November 2003, 4682 of 14 123 patients referred for amniocentesis decided to have QF-PCR as a rapid adjunct to conventional cytogenetic evaluation. Patients were classified for the risk of missing chromosomal abnormalities by QF-PCR according to anamnestic risk and ultrasound prior to amniocentesis. The results of the two defined categories were compared concerning clinically significance of cytogenetic results. Results: QF-PCR and traditional karyotyping had concordant results in 4617 of 4682 (98.6%) cases. Thirty-six of 110 (32.2%) clinically significant chromosomal abnormalities were missed by QF-PCR. Patients not at risk for missing chromosomal abnormalities with QF-PCR had a residual risk of 1/166 (0.6%) for chromosomal distortions of clinical significance. Conclusion: Classification not specifically identifies patients at risk for structural abnormalities. Clinical relevance of the not-detected anomalies essentially justifies traditional karyotyping regardless of risk-classification.