SYDNEY, AUSTRALIA – Embryonic growth discordance at 7.0-9.6 weeks’ gestation is predictive of spontaneous single fetal loss in the first trimester, regardless of chorionicity, a retrospective study has found.
Researchers examined the association between crown rump length (CRL) discordance in 1,356 twin pregnancies, measured by ultrasound at 7.0-9.6 weeks, and spontaneous single fetal demise diagnosed at the 11- to 14-week scan, and presented the data at the International Society of Ultrasound in Obstetrics and Gynecology world congress,.
Data from the STORK (Southwest Thames Obstetric Research Collaborative) cohort showed CRL discordance was associated with a significant increase in single fetal loss at 11-14 weeks (odds ratio, 1.2).
The study found a predictive accuracy of CRL discordance at 7.0-9.6 weeks of area under the curve (AUC) equals 0.93, and the degree of discordance was significantly associated with the likelihood of early fetal loss.
At least one twin having a CRL below the fifth centile also was significantly associated with single fetal loss (OR, 2.21). However, there was no relationship between single fetal loss and maternal age or chorionicity.
At the same time, another retrospective cohort study of 1,733 dichorionic twin pregnancies presented in the same session concluded that CRL discordance at 11-14 weeks was associated with, but was not a strong predictor of, adverse outcomes such as fetal loss or preterm birth.
Dr. Francesco D’Antonio, a researcher for the first study, said evidence was building that CRL discordance at the 11- to 14-week mark was not a useful indicator of pregnancy outcomes.
"This is a big issue, because most of the doctors believe that actually this is useful, and they counsel the patient about a possible occurrence of adverse outcomes," said Dr. D’Antonio of the fetal medicine unit at St George’s, University of London.
"If you see there is a discrepancy in the first trimester, don’t tell the patient that the baby is going to die, or something bad is going to happen, because the predictivity is poor," Dr. D’Antonio said in an interview.
Dr. D’Antonio said the association between CRL discordance at 7.0-9.6 weeks and fetal loss by 11-14 weeks likely reflected the fact that a not-insignificant proportion of singleton pregnancies started as multiple pregnancies, but one fetus was lost before the 11- to 14-week scan.
"We didn’t pick these up in the past because we used to scan patients at 11 weeks, so when the IVF specialists started to scan patients at 4-5-6 weeks, this phenomenon became evident," he said.
The study observed 111 cases (8.2%) of single fetal loss at 11-14 weeks.
No conflicts of interest were declared.