Abortion for fetal indications: Timing of prenatal diagnosis and abortion for structural and genetic abnormalities

To compare diagnoses in patients undergoing abortion for fetal indications at 15-0/7 to 21-6/7 vs. ≥22-0/7 weeks' gestation.

This retrospective cohort study included women undergoing abortion at ≥15-0/7 weeks' gestation for fetal indications from 2012 to 2018 at our institution. We compared indications (genetic vs. structural only) between groups by gestational age (15-0/7 to 21-6/7 vs. ≥22-0/7 weeks). We performed statistical analysis using Fisher's exact and Mann-Whitney U tests.

The 158 women identified included 97 (61.4%) at 15-0/7 to 21-6/7 and 61 (38.6%) at ≥22-0/7 weeks' gestation. Women at an earlier gestational age more commonly had an initial diagnosis of a genetic disorder (41 [42.3%)] vs.10 [16.4%], respectively, p < .001). In 69 cases with initial or subsequent diagnosis of a genetic disorder, there were differences in the types of genetic abnormalities, with common chromosomal abnormalities (including Trisomies 13, 18, and 21) the most frequent diagnosis in those who underwent abortion at 15-0/7 to 21-6/7 weeks and microarray abnormalities more common at ≥22-0/7 weeks (22 [44.9%] vs. 4 [18.2%]) and 7 [14.9%] vs. 11 [50.0%], respectively, p = .01). Routine ultrasonography for fetal anomaly surveillance occurred one week earlier in women undergoing abortion for structural anomalies at 15-0/7 to 21-6/7weeks (median 19-2/7 weeks [interquartile range (IQR) 19 0/7 to 19-5/7 weeks]) compared to ≥22-0/7 weeks (median 20-2/7 weeks [IQR 19 6/7 to 20 4/7 weeks]), p < .001.

Abortions for genetic indications are performed earlier in gestation compared to those performed for structural abnormalities. Timing of fetal anatomy ultrasound examination correlated with gestational age at abortion for structural abnormalities.

Many states impose gestational-age based abortion bans, with 20-weeks post-fertilization the most common. However, we may not identify fetal abnormalities until close to 22 weeks gestation (20-weeks post-fertilization). Optimizing timing of prenatal diagnosis might mitigate the impact of gestational-age based abortion bans.