Ultrasound detection and perinatal outcome of fetal trisomies 21, 18 and 13 in the absence of a routine fetal anomaly scan or biochemical screening

Abstract

In obstetric practice without routine biochemical or sonographic screening tests the detection of findings suggestive of aneuploidy is low for trisomy 21, but is high for trisomies 18 and 13. These findings provide information for counseling about the antenatal, intrapartum, and neonatal course of these trisomies.

Prenatal diagnosis of chromosomal abnormalities in a resource‐poor setting

“…This discrepancy may be due to incomplete ascertainment or to the choice of soft markers (the routine focus on facial profile and position of the hands may reduce the incidence of apparently isolated other markers). The detected abnormalities were as reported elsewhere [12][13][14]16,24] but, in contrast to other studies [19,22,23], trisomy 21 was the most commonly detected in our study, possibly because of our routine detailed assessment of the neck, facial profile, and crux of the heart [13,18].…”

“…The minimal contribution of first-trimester screening to the present study was due to late presentation rather than low sensitivity [15]. Our results are therefore to be chiefly compared with those of reports on second-trimester ultrasound screening and clinical features leading to late referrals [19][20][21][22][23].…”

“…We noted, as have others [14,18,19,21,22,24], that normal features or isolated soft markers were uncommon on ultrasound when karyotypic abnormalities were severe. A recent review [8] corroborates the limited contribution of isolated soft markers in our study but is in contradiction with reports of a more than 20% incidence in trisomy 21 detected with soft markers [12,14,16].…”

“…The sensitivity of ultrasound-based risk adjustment was higher in this study than in population-based studies [4,8,19], low-risk cohort studies [20,21], or studies relying on clinical suspicion before referral [22], and the difference was expected from the disparities in study design, patient selection, and modes of ascertainment. Screening sensitivity was much higher by ultrasound than by maternal age alone in our study, which concurred with population-based findings [4,8,19].…”

“…The indications for ultrasound assessment were the following: a high obstetric risk necessitating prenatal care at the hospital (2 scans, in weeks 11-14 and 18-24); genetic counseling because of age (N 36 years at conception) or because of a fetal risk of abnormality (1 or 2 scans, in weeks 11-14 and/or [16][17][18][19][20][21][22][23][24]; or an emergency referral because of an abnormal clinical course or abnormal findings on a basic scan offered before the 24th week at the primary care level.…”