Poorer survival in prenatally diagnosed trisomy 18 infants compared with postnatally diagnosed cases: a single-center...

Trisomy 18 is a common autosomal trisomy that is associated with high perinatal and infant mortality rates. With the widespread use of prenatal screening, many cases have been identified. In contrast, when the diagnosis occurs in the late prenatal period, that is, beyond the gestational limit for termination, or postnatally, careful planning for delivery and neonatal care is required. Emerging evidence suggests that intensive neonatal care can prolong survival and that the prenatal diagnosis may influence subsequent treatment choices. However, few studies have directly compared survival according to the timing of the diagnosis while accounting for treatment policy. Therefore, we compared survival between prenatally and postnatally diagnosed infants with trisomy 18, and examined whether diagnostic timing was associated with the selection of intensive care.

A retrospective study was conducted on 35 cases of trisomy 18 identified at our center between 2005 and 2024, including 25 prenatally diagnosed cases and 10 postnatally diagnosed liveborn infants. Among the prenatally diagnosed cases, 15 resulted in live births. Survival outcomes were compared between prenatally diagnosed liveborn infants (n = 15) and postnatally diagnosed liveborn infants (n = 10), and perinatal characteristics were evaluated.

Among all liveborn infants, the Kaplan-Meier estimated 12-month survival rates were 8% (95% CI [0.5%-30.6%]) in the prenatal group and 40% (95% CI [12.3%-67.0%]) in the postnatal group, with poorer survival in the prenatal group (log-rank p = 0.02). Among liveborn infants, an intensive care policy was selected significantly less frequently in the prenatal group than in the postnatal group (33.3% [5/15] vs. 90.0% [9/10], p = 0.01). In an exploratory subgroup analysis of infants who received intensive care, the Kaplan-Meier estimated 12-month survival rates were 20% (95% CI [0.8%-58.2%]) in the prenatal group and 44% (95% CI [13.6%-71.9%]) in the postnatal group. The confidence intervals were wide, and no statistically significant difference in survival was observed between the two groups (log-rank p = 0.30).

Overall survival was poorer among infants with trisomy 18 diagnosed prenatally than among those diagnosed postnatally, and this difference may be partly associated with differences in treatment policies. These findings suggest that treatment policies following prenatal diagnosis may be associated with survival duration in trisomy 18.