Trisomy 21 screening with αlpha software and the Fetal Medicine Foundation algorithm

BACKGROUND

Screening for trisomy 21 provides pregnant women with accurate risk information. Different algorithms are used to screen for trisomy 21 in South Africa (SA). The Fetal Medicine Foundation (FMF) provides software to screen for trisomy 21 in the first trimester by ultrasound or a combination of ultrasound and biochemistry (combined screening), and requires regular and stringent quality control. With αlpha software, first trimester combined screening and screening with biochemistry alone in the first or second trimester are possible. The αlpha screening requires quality control of biochemical tests, but not of ultrasound measurements. Ideally, a screening test should have a high detection and a low screen positive rate. Despite the availability of these screening programmes, only a minority of infants with trisomy 21 are detected prenatally, raising questions about the effectiveness of screening.

OBJECTIVES

To determine the screen positive and detection rates of prenatal screening for trisomy 21 in the SA private healthcare system.

METHODS

Data from the three largest laboratories collected between 2010 and 2015 were linked with genetic tests to assess screen positive and detection rates. Biochemical screening alone with αlpha software (first or second trimester) and combined screening using either FMF or αlpha software were compared.

RESULTS

One-third of an estimated 675 000 pregnancies in private practice in the 6-year study period underwent screening. There were 687 cases of trisomy 21 in 225 021 pregnancies, with only 239 (35%) diagnosed prenatally. The screen positive rates were 11.8% for first trimester biochemistry, 7.6% for second trimester biochemistry, 7.3% for first trimester FMF software ultrasound alone, 3.7% for combined first trimester screening with FMF software, and 3.5% for combined first trimester screening with αlpha software. The detection rates for a 5% false positive rate were 63% for first trimester biochemistry, 69% for second trimester biochemistry, 95% for combined first trimester screening with FMF software and 80% for combined first trimester screening with αlpha software. Detection and confirmation rates were highest with FMF software.

CONCLUSION

Screening with FMF software has a similar screen positive rate and better detection rate than screening with αlpha software. The low prenatal detection rate of trisomy 21 is mainly due to a low prevalence of screening. More research is needed in the SA setting to explore why screening and confirmatory testing after high-risk results are not performed in many pregnancies.

Impact of fetal growth restriction on pregnancy outcome in women undergoing expectant management for preterm pre-eclampsia

OBJECTIVES

To assess whether coexisting fetal growth restriction (FGR) influences pregnancy latency among women with preterm pre-eclampsia undergoing expectant management. Secondary outcomes assessed were indication for delivery, mode of delivery and rate of serious adverse maternal and perinatal outcomes.

METHODS

We conducted a secondary analysis of the Pre-eclampsia Intervention (PIE) and the Pre-eclampsia Intervention 2 (PI2) trial data. These randomized controlled trials evaluated whether esomeprazole and metformin could prolong gestation of women diagnosed with pre-eclampsia between 26 and 32 weeks of gestation undergoing expectant management. Delivery indications were deteriorating maternal or fetal status, or reaching 34 weeks' gestation. FGR (defined by Delphi consensus) at the time of pre-eclampsia diagnosis was examined as a predictor of outcome. Only placebo data from PI2 were included, as the trial showed that metformin use was associated with prolonged gestation. All outcome data were collected prospectively from diagnosis of pre-eclampsia to 6 weeks after the expected due date.

RESULTS

Of the 202 women included, 92 (45.5%) had FGR at the time of pre-eclampsia diagnosis. Median pregnancy latency was 6.8 days in the FGR group and 15.3 days in the control group (difference 8.5 days; adjusted 0.49-fold change (95% CI, 0.33-0.74); P < 0.001). FGR pregnancies were less likely to reach 34 weeks' gestation (12.0% vs 30.9%; adjusted relative risk (aRR), 0.44 (95% CI, 0.23-0.83)) and more likely to be delivered for suspected fetal compromise (64.1% vs 36.4%; aRR, 1.84 (95% CI, 1.36-2.47)). More women with FGR underwent a prelabor emergency Cesarean section (66.3% vs 43.6%; aRR, 1.56 (95% CI, 1.20-2.03)) and were less likely to have a successful induction of labor (4.3% vs 14.5%; aRR, 0.32 (95% CI, 0.10-1.00)), compared to those without FGR. The rate of maternal complications did not differ significantly between the two groups. FGR was associated with a higher rate of infant death (14.1% vs 4.5%; aRR, 3.26 (95% CI, 1.08-9.81)) and need for intubation and mechanical ventilation (15.2% vs 5.5%; aRR, 2.97 (95% CI, 1.11-7.90)).

CONCLUSION

FGR is commonly present in women with early preterm pre-eclampsia and outcome is poorer. FGR is associated with shorter pregnancy latency, more emergency Cesarean deliveries, fewer successful inductions and increased rates of neonatal morbidity and mortality. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Persistent reversed end diastolic flow in the fetal middle cerebral artery: an ominous finding

Fetal persistent middle cerebral artery reversed end diastolic flow is a rare and ominous finding. Previous cases have been associated with intracranial hemorrhage, growth restriction, anaemia, and hepatic anomaly. Intrauterine demise or early neonatal death is a common outcome. We report the case of persistent middle cerebral artery reversed end diastolic flow in a well-grown fetus at 32 weeks' gestation resulting from acute, severe anaemia due to a large feto-maternal hemorrhage. An emergency cesarean section was performed and the neonate required advanced resuscitation and immediate blood transfusion. Postnatal magnetic resonance imaging confirmed a hemorrhagic parietal infarct and bilateral ischaemic changes in the basal ganglia. This provides further evidence that persistent middle cerebral artery reversed end diastolic flow in any fetus is an ominous finding warranting urgent diagnostic evaluation and/or delivery.