Cleft Meta-Analyses

A set of studies that combine results across decades of research to better understand speech, language, and reading development in children with nonsyndromic cleft palate with or without cleft lip

Purpose

Nonsyndromic cleft palate, with or without cleft lip (often shortened to NSCP/L), is a common birth difference where the roof of the mouth does not fully close during early development. Because the palate plays a critical role in building oral air pressure and shaping speech sounds, children with NSCP/L are at increased risk for delays in speech sound development. Speech skills are foundational for learning language (words, grammar, conversation) and later reading.

Over the last several decades, many researchers have studied speech, language, and reading development in children with NSCP/L. However, findings have often been inconsistent—with some studies reporting clear delays and others suggesting that children “catch up” over time. Our goal was to resolve these inconsistencies by using meta-analysis, a research method that combines results across many studies to estimate overall patterns of development.

What is a meta-analysis?

A meta-analysis is a research method that combines and summarizes results from multiple studies that ask similar questions. Rather than relying on a single study, meta-analysis allows researchers to:

Estimate the average difference between groups across many samples
Improve confidence in results by increasing sample size
Examine why results might differ across studies

We followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) framework to ensure a transparent and rigorous review process.

How we did it

Finding the studies

We conducted comprehensive literature searches across multiple databases and hand-reviewed reference lists. Across the full project, we screened thousands of records and identified 31 eligible studies that compared children with NSCP/L to children without clefts. To be included, studies had to:

Include children with nonsyndromic cleft palate with or without cleft lip
Include a non-cleft comparison group
Measure speech, language, and/or reading skills
Include children from birth through early school age

Studies that met criteria were included in one or more of our meta-analyses depending on the skills reported.

PRISMA flow chart of study search and inclusion

*Note.* This search flowchart represents the search strategy for Lancaster and colleagues (Lancaster et al., 2020), which is considered the primary paper and search. We updated the search for our reading (Lancaster et al., 2021) and correlational (Lien et al., 2024) papers. However, the flow of the search strategy remained the same.

What skills did we examine?

For group comparisons, we calculated standardized effect sizes (Hedges’ g) to estimate differences between children with and without NSCP/L for the following areas:

Independent Speech
The range of speech sounds a child can produce, regardless of accuracy (e.g., consonant inventories from speech samples).
Speech Accuracy
How closely a child’s speech matches adult targets (e.g., percent consonants correct from single-word or connected speech tasks).
Speech Errors
The presence of speech sound errors, including cleft-related patterns and developmental errors.
Expressive Language
Language used to communicate ideas (e.g., vocabulary size, sentence length, standardized expressive language tests, parent report, language samples).
Receptive Language
Language used to understand spoken messages (e.g., receptive vocabulary, following directions, comprehension measures).
General Reading
Broad reading skills such as word reading, reading fluency, and comprehension.
Pre-Reading
Skills required to learn to read such as print awareness, phonological awareness (rhyming, blending, segmentation), and nonword repetition.

Relationships between speech and language

In a subset of studies, we also examined how early speech skills and language skills are related within children with NSCP/L by meta-analyzing correlations between:

Consonant inventory and vocabulary size
Consonant inventory and mean length of utterance (MLU)

These analyses allowed us to ask whether children who have stronger speech sound skills also tend to have stronger language skills.

What factors might explain differences?

We coded several moderators, or factors that could influence results across studies, including:

Child characteristics (e.g., age, cleft type)
Assessment characteristics (e.g., speech sampled from single words vs. conversation; standardized tests vs. parent report)
Study characteristics (e.g., publication year, country)

What we learned

Delays in speech

Across studies, young children with NSCP/L showed large and persistent delays in speech development compared to children without clefts (Lancaster et al., 2020). On average, children with NSCP/L had:

smaller consonant inventories
lower speech accuracy
more speech sound errors

Speech differences were evident from toddlerhood through early school age.

Delays in language

Children with NSCP/L also demonstrated moderate delays in expressive and receptive language (Lancaster et al., 2020). Expressive language differences tended to decrease with age, especially when language was measured using standardized tests. However, receptive language differences remained more consistent over time.

Delays in reading

School-age children with NSCP/L showed subtle but meaningful weaknesses in reading compared to peers (Lancaster et al., 2021), particularly in:

pre-reading skills, such as phonological awareness
word decoding skills

These findings suggest that early speech and language differences may place some children with NSCP/L at risk for later reading difficulties.

Summary of meta-analytic findings across speech, language, and reading

*Note.* Analyses are listed on the Y-axis. Effect sizes are plotted on the X-axis.

A meaningful link between speech and language

We found a moderate-to-strong relationship between early speech sound development and expressive language, especially vocabulary (Lien et al., 2024). Children with larger consonant inventories tended to have larger vocabularies. This suggests that early speech skills may serve as an important marker of language risk in children with NSCP/L.

Why this work matters

Together, these meta-analyses show that children with NSCP/L are at increased risk across speech, language, and reading development, even when average scores fall within the “normal” range on standardized tests. Monitoring multiple areas of communication—and especially early speech development—may support earlier identification of children who could benefit from targeted intervention.

Access our data

All project materials and extracted data are openly available through our LDbase project

https://ldbase.org/projects/e040e2b7-fcaf-4f15-a51c-906e304ae7ce

Team & support

These meta-analyses were made possible by a large and collaborative team:

Dr. Hope S. Lancaster — Project leadership, study design, data analysis, writing, visualization, and open science practices
Dr. Kari M. Lien — Study review, data extraction, and manuscript development
Ms. Paige Ellis and Ms. Jordan Haas — Literature review and data extraction

We also gratefully acknowledge consultation and feedback from:

Dr. Nancy Scherer (cleft and speech development)
Dr. Jason Chow (meta-analysis methods)
Dr. Ann Kaiser (language development)

Posters and downloads

Meta-Analysis of Early Speech and Language in Children with Nonsyndromic Cleft Palate with or without Cleft Lip
Lancaster, Lien, Chow, Frey, Scherer, & Kaiser - Conference poster April 2018 Download the poster (PDF)

Word Decoding in Children with Nonsyndromic Cleft Lip and/or Palate: Meta-Analysis
Haas, Lancaster, Lien, Ellis, & Scherer - Conference poster November 2019
Download the poster (PDF)

The Relationship Between Speech and Expressive Language in Children with Cleft Lip/Palate: A Meta-Analysis
Ellis, Lien, Lancaster, Haas, & Scherer - Conference poster November 2019
Download the poster (PDF)

Relationship Between Speech and Language Skills in Young Children with Nonsyndromic Cleft Palate with or without Cleft Lip
Ellis, Lien, Lancaster, & Scherer - Research talk November Download the poster (PDF)

References

2024

IJSLP

A meta-analysis of the relationship between speech and language development in children with nonsyndromic cleft palate with or without cleft lip

Kari M. Lien, Paige Ellis, Nancy J. Scherer, and 1 more author

International Journal of Speech-Language Pathology, Nov 2024

Abs DOI

Objective: Children with nonsyndromic cleft palate with or without cleft lip are at risk of speech production and language delays. In typical development, a strong relationship exists between speech and expressive language development. However, the understanding of this relationship in children with nonsyndromic cleft palate with or without cleft lip is incomplete. The objective of this study was to determine the average correlation between consonant inventory and two expressive language skills in children with NSCP ± L. Design: The study used a random effects meta-analyses design. Articles were included by searching PubMed, APA PsycINFO, and ERIC. Main Outcome Measures: Correlations between consonant inventory and (1) expressive vocabulary and (2) mean length of utterance. Result: Based on eight studies representing 187 children with nonsyndromic cleft palate with or without cleft lip, consonant inventory was positively correlated with expressive vocabulary size (k = 8, z = 0.74, SE = .16, p < .001, [0.424, 1.052]). Using data from four studies, representing 83 children with nonsyndromic cleft palate with or without cleft lip, consonant inventory had a positive nonsignificant correlation with mean length of utterance (k = 4, z = 0.513, SE = 0.293, p = .081, [−0.063, 1.088]). Conclusion: Results support a connection between consonant inventory and expressive vocabulary size in children with nonsyndromic cleft palate with or without cleft lip across four languages. Small consonant inventories are often associated with expressive language delays.

2021

CPCJ

Reading Development in Children With Nonsyndromic Cleft Palate With or Without Cleft Lip: Meta-analysis and Systematic Review

Hope Sparks Lancaster, Kari M. Lien, Jordan Haas, and 2 more authors

Cleft Palate Craniofacial Journal, Nov 2021

Abs DOI

We conducted a meta-analysis and systematic review of literature comparing pre-reading and general reading in school-age children with nonsyndromic cleft palate with or without cleft lip (NSCP/L) to their peers without NSCP/L. Our literature search identified 1238 possible records. After screening we identified 11 samples for inclusion for systematic review and eight for meta-analysis. We compared 292 children with NSCP/L to 311 peers for 23 pre-reading effect sizes and 17 general reading effect sizes (EFg). We conducted a random-effects metaregression using robust variance estimation. On average school-age children with NSCP/L scored lower on pre-reading (EFg = −0.36) and general reading measures (EFg = −0.38) compared to their peers. We conducted post-hoc analyses on phonological awareness and word decoding effect sizes; children with NSCP/L performed lower on phonological awareness (EFg = −0.22) and word decoding (EFg = −0.39) compared to their peers. There was weak evidence that hearing status and/or speech-language functioning might moderate reading development. There was limited evidence that age or socioeconomic status moderated reading development. However, samples did not consistently report several characteristics that were coded for this project. Our findings suggest that school-age children with NSCP/L have persistent reading problems. Further research is needed to explore reading development in children with NSCP/L, as well as the relationships among hearing, speech, language, and reading development.

2020

JSLHR

Early speech and language development in children with nonsyndromic cleft lip and/or palate: A meta-analysis

Hope Sparks Lancaster, Kari M. Lien, Jason C. Chow, and 3 more authors

Journal of Speech, Language, and Hearing Research, Nov 2020

Abs DOI

The aim of the study was to conduct a meta-analysis of research examining the early speech and language functioning of young children, birth to age 8;11 (years;months), with nonsyndromic cleft lip and/or palate (NSCL/P) compared to their peers without NSCL/P. We conducted a random-effects metaregression using 241 effect sizes from 31 studies comparing 955 young children with NSCL/P to 938 typically developing peers on measures of speech and language functioning. Moderators were sample characteristics (i.e., age, cleft type, publication year, and study location) and measurement characteristics (i.e., speech sample material, language modality and domain, and assessment type). Young children with NSCL/P scored significantly lower on measures of speech and language compared to children without NSCL/P. Children with NSCL/P had smaller consonant inventories (standardized mean difference effect size [ESg] = −1.24), less accurate articulation (ESg = −1.13), and more speech errors (ESg = 0.93) than their peers. Additionally, children with NSCL/P had poorer expressive (ESg = −0.57) and receptive (ESg = −0.59) language skills than their peers. Age and assessment type moderated effect sizes for expressive language. As children with NSCL/P aged, their expressive language performance became more similar to their peers. Expressive language effect sizes from parent reports and observational language measures (estimated effect size = −0.74) were significantly lower than those from standardized norm-referenced tests (estimated effect size = −0.45). These findings suggest that young children with NSCL/P experience delays relative to their peers across multiple speech and language constructs. Differences between children with NSCL/P and their typically developing peers appear to decrease with age.