Language Outcomes in Moderate-to-Late Preterm Infants at 2 Years of Corrected Age

Sung Hee Lee; Ju Hyun Jin; Shin Won Yoon

doi:10.5385/nm.25016

Neonatal Med > Volume 33(1); 2026 > Article

Lee, Jin, and Yoon: Language Outcomes in Moderate-to-Late Preterm Infants at 2 Years of Corrected Age

Original Article

Neonatal Medicine 2026;33(1):66-73.

Published online: May 31, 2026

DOI: https://doi.org/10.5385/nm.25016

Language Outcomes in Moderate-to-Late Preterm Infants at 2 Years of Corrected Age

Sung Hee Lee, MD

, Ju Hyun Jin, MD

, Shin Won Yoon, MD

Department of Pediatrics, National Health Insurance Service Ilsan Hospital, Goyang, Korea

Correspondence to: Shin Won Yoon, MD Department of Pediatrics, National Health Insurance Service Ilsan Hospital, 100 Ilsan-ro, Ilsandong-gu, Goyang 10444, Korea
Tel: +82-31-900-0259 Fax: +82-31-900-0343 E-mail: swyoon@nhimc.or.kr

Received December 20, 2025 Revised April 20, 2026 Accepted May 9, 2026

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

Moderate-to-late preterm (MLPT) infants born at 32 to 35 weeks of gestation are often considered to be at low risk for developmental delays. However, emerging evidence suggests vulnerabilities in language development. This study aimed to evaluate language outcomes in MLPT infants at a corrected age of approximately 2 years.

Methods

We retrospectively analyzed 82 preterm infants (29 early preterm infants aged <32 weeks; 53 MLPT) followed up at the National Health Insurance Service Ilsan Hospital Growth and Development Clinic. Language assessments included the Korean Developmental Screening Test (K-DST); Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III); and Sequenced Language Scale for Infants (SELSI).

Results

BSID-III assessments revealed a significant language delay (<–2 standard deviation) in 25.0% of early preterm infants and 10.4% of MLPT infants, with mild delays in 20.8% and 25.0%, respectively. SELSI showed significant language delay (<–2 SD) in 68.8% of early preterm and 56.0% of MLPT infants. No statistically significant differences were observed between early preterm and MLPT infants in the prevalence of severe language delay or the need for speech therapy, suggesting that MLPT infants remain at a comparable risk for language developmental difficulties. Overall, 26.4% of the infants with MLPT required speech therapy.

Conclusion

Infants with MLPT were at a considerable risk of language delay. Regular developmental surveillance, language assessment at 2 years of age, and timely intervention are essential for optimizing outcomes.

Keywords: Moderate-to-late preterm; Language development; Long-term follow-up; Sequenced Language Scale for Infants; Bayley Scales of Infant and Toddler Development, Third Edition

INTRODUCTION

The global incidence of preterm births has been increasing, partly because of advances in maternal age and the growing use of assisted reproductive technologies. Preterm infants are at an elevated risk of various developmental disorders, including delays in speech and language [1,2]. Language development is critical for communication and has broad implications for cognitive, academic, and social outcomes [3]. Therefore, early identification and intervention for language delays are essential.

The majority of preterm births (approximately 80%) are classified as moderate-to-late preterm (MLPT), defined as births between 32 and 36 weeks of gestational age (GA) [4]. Although MLPT infants have traditionally been considered to have relatively favorable developmental outcomes, accumulating evidence indicates that they are also at an increased risk of neurodevelopmental delays [4,5]. However, research on the long-term developmental outcomes of MLPT infants in Korea remains limited [6,7].

A previous study by our group has reported that Korean MLPT children at school age had a mean full-scale intelligence quotient (FSIQ) of 92.89±11.90, with 24.3% demonstrating borderline intellectual functioning (FSIQ 70–85) [8]. Another nationwide population-based study conducted by our team has determined that MLPT children were significantly more likely to have language disorders than term children (adjusted odds ratio, 1.48) [6].

Similarly, recent international studies have emphasized that MLPT infants, the largest subgroup of preterm births, should not be underestimated in terms of their risk for adverse neurodevelopmental outcomes [4,9]. A population-based study from Germany has demonstrated a persistent decline in language function among MLPT children from 20 months to 8 years of age compared with their term peers, and recommended language assessments around 2 years of corrected age to enable timely intervention [9].

Despite these findings, the long-term language outcomes of infants with MLPT in Korea remain underexplored. The present study aimed to evaluate language development at approximately 2 years of corrected age with a particular focus on infants with MLPT. A better understanding of these outcomes may inform clinical follow-ups and early intervention strategies for this vulnerable population.

MATERIALS AND METHODS

1. Study population

This retrospective study included 119 preterm infants who visited the Growth and Development Clinic at the National Health Insurance Service Ilsan Hospital between January 2020 and June 2023 for follow-up at a corrected age of 18 to 24 months. The clinic provides regular medical evaluations, developmental assessments, and counseling for preterm infants born at <36 weeks of gestation and high-risk full-term infants.

Infants born at ≥36 weeks of gestation (n=9) and those lost to follow-up (n=28) were excluded. The remaining participants were classified into two groups according to their GA: early preterm (<32 weeks GA) and MLPT (32–35 weeks GA) (Figure 1).

2. Study design

Maternal and neonatal data were obtained from electronic medical records. Maternal variables, including age, nationality, mode of delivery, obstetric complications (hypertension and gestational diabetes mellitus), and depressive symptoms, were assessed using a validated questionnaire. Neonatal variables included GA, birth weight, sex, plurality, Apgar scores, presence of respiratory distress syndrome (RDS) treated with surfactant, ventilator use and duration, patent ductus arteriosus (PDA) treatment, intraventricular hemorrhage ≥grade III, periventricular leukomalacia, and length of neonatal intensive care unit (NICU) stay.

Maternal depressive symptoms were evaluated using the Korean version of the Center for Epidemiologic Studies Depression Scale (CES-D), a standardized self-report questionnaire [10]. Mothers were categorized into three groups based on CES-D scores: (1) mild depressive symptoms (16–20), (2) moderate depressive symptoms (21–24), and (3) severe depressive symptoms (≥25).

Developmental assessments were conducted at approximately 2 years of corrected age using standardized instruments, such as the Korean Developmental Screening Test (K-DST), Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III), and Sequenced Language Scale for Infants (SELSI).

The K-DST evaluates six developmental domains: gross motor function, fine motor function, cognition, language, sociality, and self-help. Results are categorized into five levels: high (above +1 standard deviation [SD]), average (–1 to 1 SD), follow-up test required (–2 to –1 SD), further evaluation (<–2 SD), and others. Infants classified as ‘follow-up test required’ or ‘further evaluation’ were defined as the delayed group [11].

The BSID-III evaluates cognitive, language, motor, socioemotional, and adaptive behavioral domains. Scores were classified as normal (≥85: ≥–1 SD), mildly delayed (70–84: –2 to –1 SD), or significantly delayed (<70: <–2 SD) [12].

Language ability was assessed using SELSI, a standardized Korean assessment tool for infants and toddlers aged 4 to 35 months [13]. The SELSI evaluates receptive and expressive language, including pragmatics, semantics, phonology, and grammar. Scores below −2 SD were classified as significant language delay [14].

3. Statistical analysis

Statistical analyses were performed using jamovi version 2.6.44.0 (The jamovi project). Categorical variables are presented as numbers (%) and continuous variables as means±SDs or as medians (interquartile ranges). Group differences between early preterm and MLPT infants were analyzed using the chi-square test or Fisher’s exact test for categorical variables. Statistical significance was defined as P<0.05.

Multivariate logistic regression analysis was additionally performed among infants who underwent the Bayley assessment, adjusting for sex, small for gestational age (SGA) status, and NICU morbidity.

RESULTS

1. Characteristics of infants and mothers

A total of 82 preterm infants were included: 29 early preterm infants (mean GA, 29.8±1.3 weeks; mean birth weight, 1,336.2± 234.5 g) and 53 MLPT infants (mean GA, 33.7±0.9 weeks; mean birth weight, 1,984.9±367.1 g) (Table 1).

Neonatal morbidities, including low Apgar scores, RDS, use of invasive ventilators, duration of ventilator support, duration of NICU admission, and treatment of PDA were significantly more frequent in early preterm infants than in MLPT infants (P<0.05). No statistically significant differences were observed between the two groups in terms of severe maternal depressive symptoms (19% in the early preterm group vs. 14% in the MLPT group, P=0.721).

2. Language development outcomes

The K-DST was completed by 79.3% of early preterm infants and 66.0% of MLPT infants. Among infants who completed the K-DST, 8.7% of early preterm infants and 14.3% of MLPT infants scored below −2 SD in the language domain. When language delay was defined as a score below −1 SD, the prevalence was 30.4% and 31.4% in early preterm and MLPT infants, respectively.

The BSID-III was performed in 82.8% of early preterm infants and 90.6% of MLPT infants. Among infants who underwent the BSID-III, 25.0% of early preterm infants and 10.4% of MLPT infants scored ≤70 in the language domain, indicating significant language delay. Mild language delay (scores 70–84) was observed in 20.8% of early preterm and 25.0% of MLPT infants. Overall, 35.4% of the MLPT infants had language scores <85, indicating a risk of language delay. The proportion of infants requiring speech therapy was 34.5% among early preterm infants and 26.4% among MLPT infants.

SELSI was administered to 55.2% of early preterm and 47.2% of the MLPT infants at a mean age of 24 to 25 months. Among those tested, 68.8% of early preterm and 56.0% of MLPT infants scored below –2 SD, indicating significant language delay.

No statistically significant differences were observed between early preterm and MLPT infants in the prevalence of severe language delay or the need for speech therapy, suggesting that MLPT infants remain at a comparable risk for language developmental difficulties.

The MLPT group demonstrated better outcomes in the cognitive domain. In the cognitive domain, 20.8% of early preterm infants scored below –2 SD, compared with 2.1% of MLPT infants (P=0.014) (Table 2).

Multivariate logistic regression analysis, including sex, SGA status, and NICU morbidity, showed no significant association with language delay.

DISCUSSION

Investigating whether MLPT birth affects language development revealed that infants with MLPT at a corrected age of approximately 2 years are also at risk of language delays and often require speech and language therapy. Although MLPT infants have higher GAs and fewer neonatal complications than early preterm infants, their risk of language delay remains substantial. These results highlight the importance of continuous developmental surveillance and timely intervention in all preterm infants, including those with the MLPT.

Concerns regarding the long-term developmental outcomes of MLPT infants are growing [15-17]. Because MLPT infants typically experience more favorable short-term morbidities and shorter NICU stays than early preterm infants, long-term follow-up is often insufficient. Consequently, subtle but clinically meaningful developmental difficulties, particularly in language, may go unnoticed in early childhood.

Previous studies have reported similar results. An Australian longitudinal cohort study demonstrated that MLPT infants exhibited developmental delays compared with their term-born peers, with the most pronounced deficits observed in the language domain [4]. Similarly, the Bavarian Longitudinal Study has revealed that MLPT infants were at significantly higher risk for poorer language outcomes than term-born children [9]. Another recent study in Spain has reported a significant language developmental delay in the MLPT group compared with their full-term peers [17]. Meanwhile, studies on MLPT infants in Korea remain scarce. To the best of our knowledge, this is the first Korean study to comprehensively evaluate language performance in MLPT infants using both the SELSI and BSID-III, thereby providing valuable insights into their early language development.

In the K-DST language domain, no statistically significant differences in language delay were observed between early preterm and MLPT infants. Early preterm (8.7%) and MLPT (14.3%) infants scored below two SDs, with a slightly higher proportion in the MLPT group. When language delay was defined as a score below –1 SD, the prevalence was 30.4% in early preterm infants and 31.4% in MLPT infants. As the K-DST is a parent-reported questionnaire, these findings may reflect subjective parental perceptions rather than objective developmental differences [11]. In addition, the K-DST was administered to a higher proportion of early preterm infants (79.3%) than MLPT infants (66.0%), raising the possibility of selection bias, whereby MLPT infants who underwent the K-DST assessment may have been perceived to be at higher developmental risk. Both the BSID-III and SELSI, which are clinician-administered assessments, have demonstrated that early preterm and MLPT infants have an increased risk of language delays [12,13].

When examining other developmental domains of BSID-III, the MLPT group demonstrated better cognitive outcomes than the early preterm group. However, in the language domain, no significant differences were observed between the two groups, and both groups showed a high prevalence of language delay (mild language delay: 20.8% vs. 25.0%; significant language delay: 25.0% vs. 10.4%). Thus, language development may remain particularly vulnerable even in MLPT infants, supporting previous studies reporting pronounced developmental delays in the language domain [4,9]. Therefore, heightened awareness of the risk of language delay and timely initiation of speech and language interventions are crucial to support optimal developmental trajectories in this population.

The mechanisms underlying language delay in MLPT infants are likely multifactorial [18]. Although these infants usually avoid the severe complications observed in extremely preterm infants, subtle neurological immaturity, altered brain connectivity, and limited early language exposure may contribute to developmental vulnerability [19]. In addition, maternal psychological factors, including postpartum depression, can affect the quality of parent–infant interaction and consequently influence language development [20-24]. In the present study, maternal depressive symptoms were observed in 47.6% of mothers of early preterm infants and 41.2% of mothers in the MLPT group. Severe depressive symptoms (scores ≥25), which are more strongly associated with a Diagnostic and Statistical Manual of Mental Disorders-based diagnosis of major depressive disorder [24], were observed in 19.0% and 14.0% of the patients in the two groups, respectively. These findings indicate a high prevalence in both groups, with no statistically significant differences between them. Therefore, screening for maternal mental health should be considered an essential component of follow-up care to support optimal developmental outcomes in preterm infants.

As MLPT infants constitute the majority of preterm births, their developmental challenges have significant public health and socioeconomic implications [25]. The potential long-term consequences of language delay in this large population highlight the need for early detection and intervention strategies [26,27]. Language delay in early childhood can extend beyond communication difficulties, affecting later academic performance, social competence, and emotional well-being [6,8,28]. Therefore, recognizing and addressing language delay at an early stage is essential to promote optimal long-term developmental and educational outcomes [29-31].

This study has some limitations. First, it was conducted at a single center with a relatively small sample size, which may limit its generalizability. SELSI was performed in 16 (55.2%) early preterm infants and 25 (47.2%) MLPT infants. SELSI was preferentially administered to high-risk infants, which may have resulted in a relatively high proportion of language delays among the infants assessed (68.8% in early preterm infants and 56.0% in MLPT infants). However, when considering the entire cohort, the overall prevalence of language delay was 37.9% in early preterm infants and 26.4% in MLPT infants. In addition, objective clinician-administered BSID assessments were conducted in 90.6% of MLPT infants, of whom 35.4% scored <85. This finding is consistent with the observed need for language therapy in 26.4% of infants in this group. Second, owing to the small sample size, we were unable to analyze the risk factors for language delay in the MLPT group. Third, because the follow-up clinic at our institution enrolled only infants born at <36 weeks’ gestation, those born at 36 weeks’ gestation were not included in the present study, although they were classified as late preterm infants. Finally, because a full-term control group was not included, a direct comparison with term-born peers was not possible.

Nevertheless, this study has important clinical implications. To the best of our knowledge, this is the first Korean study to comprehensively assess language outcomes in MLPT infants using two standardized tools (SELSI and BSID-III). This dual-assessment approach provides objective evidence-based insights into language development, an area that has been relatively under-recognized in this population. Although a full-term control group was not included for comparison, the developmental performance of these preterm infants can still be interpreted relative to population norms because the BSID-III provides standardized normative data (mean±SD, 100±15), and SELSI results are reported as percentiles. A previous Korean study has demonstrated a significant correlation between the K-BSID-III language scale and SELSI scores, suggesting that the K-BSID-III is a useful tool for predicting language developmental delay, particularly in infants with mild or definite delay [32]. In the context of the limited data available in Korea, our findings add clinically meaningful evidence to support developmental surveillance and early intervention strategies for MLPT infants. Previous Korean studies have reported that 27.5% of infants born at ≥28 weeks of gestation showed language delay when assessed using the BSID-III [33]. Data from the Korean Neonatal Network (KNN) have indicated that 18% of very-low-birth-weight infants required language support by 3 years of age, although the KNN cohort included only infants born at <32 weeks, limiting long-term outcome data to very preterm infants [34]. In our study, speech therapy was administered to 26.4% of MLPT infants, highlighting that even MLPT infants remain at risk for language difficulties.

In conclusion, MLPT infants, who are often considered to be at a lower developmental risk, may experience language delays comparable to those of early preterm infants. These results underscore the importance of regular developmental surveillance, including formal language assessment at approximately 2 years of corrected age and early intervention to improve long-term neurodevelopmental outcomes in MLPT infants.

ARTICLE INFORMATION

Ethical statement

This study was approved by the Institutional Review Board of the National Health Insurance Service Ilsan Hospital (IRB No. NHIMC 2023-03-049), and the requirement for informed consent was waived.

Conflicts of interest

No potential conflict of interest relevant to this article was reported.

Author contributions

Conception or design: S.H.L., J.H.J., S.W.Y.

Acquisition, analysis, or interpretation of data: S.H.L., S.W.Y.

Drafting the work or revising: S.H.L., J.H.J., S.W.Y.

Final approval of the manuscript: All authors read and approved the final manuscript.

Funding

None

Acknowledgments

None

Figure 1.

The flow chart of the study population. Abbreviations: NHIS, National Health Insurance Service; GA, gestational age.

Table 1.

The Characteristics of Preterm Infants and Their Mothers

Characteristic	<32 weeks (n=29)	32–35 weeks (n=53)	P-value
Gestational age (wk)	29.8±1.3 (26.4–31.7)	33.7±0.9 (32.0–35.3)	<0.001^*
26–27	3	-
28–29	12	-
30–31	14	-
32–33	-	31
34–35	-	22
Birth weight (g)	1,336.2±234.5 (820–1,840)	1,984.9±367.1 (1,090–2,680)	<0.001^*
Male sex	19 (65.5)	27 (50.9)	0.204
SGA	2 (6.9)	5 (9.4)	1.000
Apgar
1 min	5 (4–5)	6 (5–7)	<0.001^*
5 min	7 (6–7)	8 (7–9)	<0.001^*
5 min <7	12 (41.4)	8 (15.1)	0.008^*
Twin	13 (44.8)	26 (49.1)	0.714
Cesarean section	24 (82.8)	47 (88.7)	0.507
RDS treated by surfactant	28 (96.6)	18 (34.0)	<0.001^*
Invasive ventilator	24 (82.8)	13 (24.5)	<0.001^*
Duration of invasive ventilator (d)	5 (2–7)	1 (1–2)	<0.001^*
Duration of NICU admission (d)	63 (57–66)	23 (15–39)	<0.001^*
IVH (≥ grade III) or PVL	1 (3.4)	0	0.354
PDA treatments	6 (20.7)	1 (1.9)	0.007^*
Maternal age at birth (yr)	33.8±4.5	34.8±3.9	0.340
Maternal hypertension or DM	2 (6.9)	6 (11.3)	0.706
Non-Korean mother	3 (10.3)	4 (7.5)	0.694
Maternal education (≥college)	14 (48.3)	24 (45.3)	0.795
Maternal depression scale
16–20 (mild depressed)	5 (23.8)	8 (16.0)	0.507
21–24 (moderate depressed)	1 (4.8)	6 (12.0)	0.665
≥25 (severe depressed)	4 (19.0)	7 (14.0)	0.721
Depression	10 (47.6)	21 (41.2)	0.616

Values are expressed as mean±standard deviation (range), number (%), or median (interquartile range).

^* P<0.05.

Abbreviations: SGA, small for gestational age; RDS, respiratory distress syndrome; NICU, neonatal intensive care unit; IVH, intraventricular hemorrhage; PVL, periventricular leukomalacia; PDA, patent ductus arteriosus; DM, diabetes mellitus.

Table 2.

Language Assessment Outcomes in Preterm Infants at 2 Years of Corrected Age

Variable	<32 weeks (n=29)	32–35 weeks (n=53)	P-value
K-DST response	23 (79.3)	35 (66.0)	0.207
Age at test (mo)	19.5±1.7	19.5±1.8	0.987
Language
–2 SD to –1 SD	5/23 (21.7)	6/35 (17.1)	0.738
–2 SD	2/23 (8.7)	5/35 (14.3)	0.692
Cognitive
–2 SD to –1 SD	0/23 (0.0)	3/35 (8.6)	0.270
–2 SD	4/23 (17.4)	2/35 (5.7)	0.202
Gross motor
–2 SD to –1 SD	4/23 (17.4)	3/35 (8.6)	0.418
–2 SD	1/23 (4.3)	1/35 (2.9)	1.000
Fine motor
–2 SD to –1 SD	6/23 (26.1)	9/35 (25.7)	0.975
–2 SD	1/23 (4.3)	1/35 (2.9)	1.000
BSID-III	24 (82.8)	48 (90.6)	0.314
Age at test (mo)	19 (18–22)	19 (18–20)	0.502
Language
Mean	90.0±25.4	91.1±16.8	0.854
–2 SD to –1 SD (70–84)	5/24 (20.8)	12/48 (25.0)	0.695
–2 SD (<70)	6/24 (25.0)	5/48 (10.4)	0.163
Cognitive
Mean	85.2±18.7	96.3±17.8	0.135
–2 SD to –1 SD (70–84)	4/24 (16.7)	8/48 (16.7)	1.000
–2 SD (<70)	5/24 (20.8)	1/48 (2.1)	0.014^*
Motor
Mean	96.5±16.2	102.5±15.6	0.017^*
–2 SD to –1 SD (70–84)	4/24 (16.7)	7/48 (14.6)	1.000
–2 SD (<70)	1/24 (4.2)	1/48 (2.1)	1.000
SELSI	16 (55.2)	25 (47.2)	0.488
Age at test (mo)	23.5 (22–27)	25 (24–26)	0.435
<–2 SD	11/16 (68.8)	14/25 (56.0)	0.505
Speech therapy	10/29 (34.5)	14/53 (26.4)	0.443

Values are expressed as number (%), mean±standard deviation, or median (interquartile range).

^* P<0.05.

Abbreviations: K-DST, Korean Developmental Screening Test; SD, standard deviation; BSID-III, Bayley Scales of Infant and Toddler Development, Third Edition; SELSI, Sequenced Language Scale for Infants.

REFERENCES

1. Lee YK, Lee HJ. Prevalence of developmental language delay among toddlers born as preterm. Commun Sci Disord 2016;21:60–8.

2. Perez-Pereira M. Prevalence of language delay among healthy preterm children, language outcomes and predictive factors. Children (Basel) 2021;8:282.

3. Wolke D, Samara M, Bracewell M, Marlow N, EPICure Study Group. Specific language difficulties and school achievement in children born at 25 weeks of gestation or less. J Pediatr 2008;152:256–62.

4. Cheong JL, Doyle LW, Burnett AC, Lee KJ, Walsh JM, Potter CR, et al. Association between moderate and late preterm birth and neurodevelopment and social-emotional development at age 2 years. JAMA Pediatr 2017;171:e164805.

5. Shin SM. Should we regularly evaluate the neurodevelopmental status of moderate and late preterm infants? Clin Exp Pediatr 2020;63:217–8.

6. Jin JH, Lee SH, Youk TM, Yoon SW. Long-term outcomes of preterm infants in the first 6 years of life: a nationwide population-based study in Korea. Eur J Pediatr 2023;182:641–50.

7. Nam YS, Heo JS, Byeon JH, Lee EH. Neurodevelopmental outcomes of moderate-to-late preterm infants. Neonatal Med 2020;27:159–66.

8. Jin JH, Yoon SW, Song J, Kim SW, Chung HJ. Long-term cognitive, executive, and behavioral outcomes of moderate and late preterm at school age. Clin Exp Pediatr 2020;63:219–25.

9. Putnick DL, Bornstein MH, Eryigit-Madzwamuse S, Wolke D. Long-term stability of language performance in very preterm, moderate-late preterm, and term children. J Pediatr 2017;181:74–9.e3.

10. Cho MJ, Kim KH. Use of the center for epidemiologic studies depression (CES-D) scale in Korea. J Nerv Ment Dis 1998;186:304–10.

11. Kim D, Choe YJ, Durrani BAZ, Kim E, Byeon J, Eun BL, et al. Korean Developmental Screening Test for Infants and Children (K-DST): development, applications, and implications for future early childhood development interventions. Clin Exp Pediatr 2023;66:288–93.

12. Albers CA, Grieve AJ. Test Review: Bayley, N. (2006). Bayley Scales of Infant and Toddler Development– Third Edition. San Antonio, TX: Harcourt Assessment. J Psychoeduc Assess 2007;25:180–90.

13. Kim YT, Kim KH, Yoon HR, Kim WS. Sequenced language scale for infants (SELSI). Special Education Publication Co.; 2003.

14. Lee YK, Lee HJ. Development of intentional communicative behavior in Korean toddlers 12 to 30 months. Commun Sci Disord 2016;21:553–66.

15. Song IG. Neurodevelopmental outcomes of preterm infants. Clin Exp Pediatr 2023;66:281–7.

16. Mitha A, Chen R, Razaz N, Johansson S, Stephansson O, Altman M, et al. Neurological development in children born moderately or late preterm: national cohort study. BMJ 2024;384:e075630.

17. Palomero-Sierra B, Sanchez-Gomez V, Magan-Maganto M, Bejarano-Martin A, Ruiz-Ayucar I, de Vena-Diez VB, et al. Early social communication and language development in moderate-to-late preterm infants: a longitudinal study. Front Psychol 2025;16:1556416.

18. Ionio C, Riboni E, Confalonieri E, Dallatomasina C, Mascheroni E, Bonanomi A, et al. Paths of cognitive and language development in healthy preterm infants. Infant Behav Dev 2016;44:199–207.

19. Vohr BR. Neurodevelopmental outcomes of extremely preterm infants. Clin Perinatol 2014;41:241–55.

20. Rogers A, Obst S, Teague SJ, Rossen L, Spry EA, Macdonald JA, et al. Association between maternal perinatal depression and anxiety and child and adolescent development: a meta-analysis. JAMA Pediatr 2020;174:1082–92.

21. Liu Y, Kaaya S, Chai J, McCoy DC, Surkan PJ, Black MM, et al. Maternal depressive symptoms and early childhood cognitive development: a meta-analysis. Psychol Med 2017;47:680–9.

22. Yamada M, Tanaka K, Arakawa M, Miyake Y. Perinatal maternal depressive symptoms and risk of behavioral problems at five years. Pediatr Res 2022;92:315–21.

23. Kleine I, Vamvakas G, Lautarescu A, Falconer S, Chew A, Counsell S, et al. Postnatal maternal depressive symptoms and behavioural outcomes in term-born and preterm-born toddlers: a longitudinal UK community cohort study. BMJ Open 2022;12:e058540.

24. Haringsma R, Engels GI, Beekman AT, Spinhoven P. The criterion validity of the Center for Epidemiological Studies Depression Scale (CES-D) in a sample of self-referred elders with depressive symptomatology. Int J Geriatr Psychiatry 2004;19:558–63.

25. Jin JH, Lee SA, Yoon SW. Medical utilization and costs in preterm infants in the first 6 years of life after discharge from neonatal intensive care unit: a nationwide population-based study in Korea. J Korean Med Sci 2022;37:e93.

26. Zambrana IM, Vollrath ME, Sengpiel V, Jacobsson B, Ystrom E. Preterm delivery and risk for early language delays: a sibling-control cohort study. Int J Epidemiol 2016;45:151–9.

27. Ivanashvili T. Prematurity and language developmental outcomes in preschool age. Mod Med Manag 2021;2:33–45.

28. Francois C, Rodriguez-Fornells A, Cerda-Company X, Agut T, Bosch L. Impact of late to moderate preterm birth on minimal pair word-learning. Child Dev 2025;96:203–16.

29. Adams KA, Marchman VA, Loi EC, Ashland MD, Fernald A, Feldman HM, et al. Caregiver talk and medical risk as predictors of language outcomes in full term and preterm toddlers. Child Dev 2018;89:1674–90.

30. Loeffler MT, Daikeler J, Wagner L, Natalucci G, Daum MM. Early expressive and receptive language development in preterm vs full-term children: a meta-analysis. Pediatrics 2025;156:e2024070477.

31. Agyeman-Duah J, Kennedy S, O'Brien F, Natalucci G. Interventions to improve neurodevelopmental outcomes of children born moderate to late preterm: a systematic review protocol. Gates Open Res 2021;5:78.

32. Doh JH, Kim SA, Oh K, Kim Y, Park N, Park S, et al. The predictive value of language scales: Bayley Scales of Infant and Toddler Development Third Edition in correlation with Korean sequenced language scale for infant. Ann Rehabil Med 2020;44:378–85.

33. Ahn SH, Kim SA. Assessment of preterm infants using the Bayley-III Scales in Korea. Ann Rehabil Med 2017;41:843–50.

34. Jeon GW, Lee JH, Oh M, Chang YS. Serial long-term growth and neurodevelopment of very-low-birth-weight infants: 2022 update on the Korean Neonatal Network. J Korean Med Sci 2022;37:e263.