Temporal trends in ankyloglossia and frenotomy in British Columbia, Canada, 2004-2013: a population-based study
===============================================================================================================

* K.S. Joseph
* Brooke Kinniburgh
* Amy Metcalfe
* Neda Razaz
* Yasser Sabr
* Sarka Lisonkova

## Abstract

**Background:** Routine surveillance of congenital anomalies has shown recent increases in ankyloglossia (tongue-tie) in British Columbia, Canada. We examined the temporal trends in ankyloglossia and its surgical treatment (frenotomy).

**Methods:** We conducted a population-based cohort study involving all live births in British Columbia from Apr. 1, 2004, to Mar. 31, 2014, with data obtained from the province's Perinatal Data Registry. Spatiotemporal trends in ankyloglossia and frenotomy, and associations with maternal and infant characteristics, were quantified using logistic regression analysis.

**Results:** There were 459 445 live births and 3022 cases of ankyloglossia between 2004 and 2013. The population incidence of ankyloglossia increased by 70% (rate ratio 1.70, 95% confidence interval [CI] 1.44-2.01), from 5.0 per 1000 live births in 2004 to 8.4 per 1000 in 2013. During the same period, the population rate of frenotomy increased by 89% (95% CI 52%-134%), from 2.8 per 1000 live births in 2004 to 5.3 per 1000 in 2013. The 2 regional health authorities with the lowest population rates of frenotomy (1.5 and 1.8 per 1000 live births) had the lowest rates of ankyloglossia and the lowest rates of frenotomy among cases with ankyloglossia, whereas the 2 regional health authorities with the highest population rates of frenotomy (5.2 and 5.3 per 1000 live births) had high rates of ankyloglossia and the highest rates of frenotomy among cases of ankyloglossia. Nulliparity, multiple birth, male infant sex, birth weight and year were independently associated with ankyloglossia.

**Interpretation:** Large temporal increases and substantial spatial variations in ankyloglossia and frenotomy rates were observed that may indicate a diagnostic suspicion bias and increasing use of a potentially unnecessary surgical procedure among infants.

Public health surveillance of congenital anomalies has a long tradition based in part on the lessons learned following experience with thalidomide and phocomelia,1,2 and diethylstilbestrol and vaginal adenocarcinoma.3 Outbreaks of congenital rubella syndrome have also served to reinforce the case for routine surveillance of congenital anomalies.4 In Canada, there has been an increased focus on such surveillance over the previous decade, with the Public Health Agency of Canada providing regular reports on neural tube and congenital heart defects, Down syndrome, orofacial clefts, limb deficiency defects and gastroschisis.5

Recent surveillance activities carried out as part of routine monitoring of population perinatal health in the province of British Columbia, Canada,6 led to the identification of a temporal increase in ankyloglossia (tongue-tie). The condition, characterized by an unusually short, thick or tight band of tissue (lingual frenulum) that limits the range of movement of the tongue, may interfere with feeding and speech. The unexpected increase in ankyloglossia in the province was initially categorized as an incidental finding and dismissed as being of no clinical or public health importance. However, clinicians and hospital staff attributed the rise to increased ascertainment owing to the Baby-Friendly Hospital Initiative of the World Health Organization (WHO) and UNICEF and to support for breastfeeding.7 Increased focus on breastfeeding initiation before hospital discharge may have led to heightened diagnostic suspicion of ankyloglossia and a potential increase in surgical correction of the condition (frenotomy). We carried out a population-based study to examine the temporal trends and epidemiologic correlates in ankyloglossia.

## Methods

We conducted a population-based cohort study involving all live births in British Columbia, Canada, using data obtained from the province's Perinatal Data Registry. This database contains detailed information on all mothers and babies in the province that is collated by trained medical record abstractors using standardized forms and coding rules. Data quality is continually assessed by means of logic and consistency checks, and information in the database has been validated8,9 and used extensively for health planning and research.10 

We restricted the study period to fiscal years from Apr. 1, 2004, to Mar. 31, 2014 (hereafter referred to as years 2004 to 2013), when diagnoses and procedures among mothers and babies were consistently coded with the enhanced Canadian version of the 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10-CA) and the Canadian Classification of Health Interventions (CCI), respectively.

Appropriate diagnostic and procedure codes were used to identify cases of ankyloglossia (ICD-10-CA code Q381) and tongue release (CCI code [1.FJ.72](http://1.FJ.72) for lingual frenectomy/frenotomy/frenulectomy or glossotomy for tongue-tie). We first examined rates of ankyloglossia by year, maternal characteristics (parity, body mass index [BMI] and plurality) and infant characteristics (sex, birth weight and gestational age). Rates of ankyloglossia were also quantified by length of hospital stay. The frequency of ankyloglossia and frenotomy was examined as a function of the rate of breast milk feeding and by regional health authority. The frequency of frenotomy among cases of ankyloglossia was examined by year to ascertain whether surgery was being increasingly used to treat the condition, and by regional health authority to ascertain potential spatial variation in surgery rates.

The precision of rate estimates was quantified using exact binomial 95% confidence intervals (CIs), and the significance of temporal trends in rates was evaluated using a χ2 test for linear trend in proportions. Associations between year, maternal characteristics and infant characteristics, and ankyloglossia were quantified using proportion type rate ratios with 95% CIs. Logistic regression was used to obtain adjusted odds ratios expressing the association between year, maternal characteristics and infant characteristics, and ankyloglossia. Because the frequency of ankyloglossia was low, odds ratios obtained from logistic models were interpreted as rate ratios. All analyses were carried out using SAS version 9.3 (SAS Institute Inc.). 

The study was approved by the Research Ethics Board of the University of British Columbia.

## Results

There were 459 445 live births and 3022 cases of ankyloglossia in the province during the study period, for a birth prevalence of 6.6 cases per 1000 live births (95% CI 6.3-6.8). The rate of ankyloglossia increased from 5.0 (95% CI 4.3-5.7) per 1000 live births in 2004 to 6.4 (95% CI 5.7-7.2) per 1000 in 2008, and to 8.4 (95% CI 7.6-9.3) per 1000 in 2013 (*p* for linear trend < 0.001; Figure 1A). Rates of ankyloglossia varied significantly between the 5 regional health authorities; the lowest and highest rates were 3.8 per 1000 and 8.2 per 1000 live births, respectively (odds ratio for highest v. lowest 2.15, 95% CI 1.92-2.40).

![Figure 1](http://www.cmajopen.ca/https://www.cmajopen.ca/content/cmajo/4/1/E33/F1.medium.gif)

[Figure 1](http://www.cmajopen.ca/content/4/1/E33/F1)

Figure 1 
Rates of ankyloglossia and frenotomy by year (A) and by proportion of infants who were breast milk fed (B), and temporal trends in frenotomy among ankyloglossia cases (C).

The frequency of ankylogossia decreased with maternal age; infants of women aged 40 years or more were 0.81 (95% CI 0.66-1.00) times as likely to have ankyloglossia as infants of mothers aged 20-24 years (Table 1). The declining trend in ankyloglossia with increasing maternal age was not statistically significant (*p* for linear trend 0.20). Infants of nulliparous women and women with a BMI of 30 or greater had relatively high rates of ankyloglossia; the *p* value for the linear trend in ankyloglossia rates with increasing BMI was 0.06. Male infant sex was associated with a higher rate of ankyloglossia (rate ratio 1.72, 95% CI 1.60-1.85), whereas preterm infants had relatively lower rates compared with term and post-term infants (*p* for linear trend < 0.001). Birth weight was also associated with ankyloglossia: compared with infants with a birth weight of 3000-3499 g, those weighing less than 3000 g had relatively low rates and infants with birth weights of 4000 g or more had relatively high rates. There was a significant linear trend in ankyloglossia rates with increasing birth weight (*p* < 0.001).

View this table:
[Table 1:](http://www.cmajopen.ca/content/4/1/E33/T1)

Table 1:   Frequency of ankyloglossia by maternal and infant characteristics among all live births, British Columbia, Canada, 2004-2013

Table 2 shows the association between the length of hospital stay for the infant during the birth admission and rates of ankyloglossia. Rates of ankyloglossia increased steadily from 3.6 per 1000 live births among infants discharged within 24 hours after birth to 9.3 per 1000 among infants discharged 96-167 hours after birth. Infants whose hospital stay was 168 hours or longer had an ankyloglossia rate of 4.7 per 1000 live births.

View this table:
[Table 2:](http://www.cmajopen.ca/content/4/1/E33/T2)

Table 2:   Frequency of ankyloglossia by length of infant's hospital stay among all live births, British Columbia, Canada, 2004-2013

Table 3 presents the results of the logistic regression analyses carried out among term infants. Significant determinants of ankyloglossia included nulliparity (v. multiparity; adjusted rate ratio [aRR] 1.47, 95% CI 1.36-1.59), BMI of 30 or greater (v. BMI 18-24; aRR 1.14, 95% CI 1.00-1.30), multiple birth (v. singleton; aRR 0.68, 95% CI 0.63-0.74), male infant sex (v. female; aRR1.74, 95% CI 1.61-1.89), and birth weight of 4000-4499 g and of 4500 g or more (v. 3000-3499 g; aRR 1.26, 95% CI 1.12-1.42, and aRR 1.39, 95% CI 1.11-1.76, respectively). Adjusted rates of ankyloglossia were also significantly higher in the years 2008 to 2013 compared with 2004 (aRR 1.70, 95% CI 1.43-2.02).

View this table:
[Table 3:](http://www.cmajopen.ca/content/4/1/E33/T3)

Table 3:   Logistic regression analysis showing association between maternal and infant determinants and ankyloglossia among term and post-term (37-43 wk) live births, British Columbia, Canada, 2004-2013

There were 1765 frenotomy procedures carried out in the study population, for a frenotomy rate of 3.8 (95% CI 3.7-4.0) per 1000 live births. The rate of frenotomy increased by 89% (95% CI 52%-134%), from 2.8 per 1000 live births in 2004 to 5.3 per 1000 live births in 2013. The association between maternal and infant characteristics and frenotomy among term infants (Table 4) was similar in direction and magnitude to the association between maternal and infant characteristics and ankyloglossia (Table 3).

View this table:
[Table 4:](http://www.cmajopen.ca/content/4/1/E33/T4)

Table 4:   Logistic regression analysis showing association between maternal and infant determinants and frenotomy among term and post-term (37-43 wk) live births, British Columbia, Canada, 2004-2013

The temporal increase in frenotomy rates paralleled the temporal increase in ankyloglossia rates (Figure 1A), and annual rates of ankyloglossia and frenotomy were closely correlated (correlation coefficient 0.98, *p* < 0.001). Rates of frenotomy varied between the different health authorities, with the lowest and highest rates being 1.8 per 1000 live births and 5.3 per 1000 (odds ratio for highest v. lowest 2.99, 95% CI 2.49-3.58). Both ankyloglossia and frenotomy rates increased as rates of breast milk feeding increased from 93% to 95% (Figure 1B); annual rates of ankyloglossia and frenotomy were closely correlated with breast milk feeding (correlation coefficient 0.93, *p* < 0.001 for ankyloglossia; correlation coefficient 0.92, *p* < 0.001 for frenotomy).

The rate of frenotomy among ankyloglossia cases was 58.0%; this rate increased nonsignificantly and in a nonlinear fashion from 57.1% in 2004 to 63.5% in 2013 (11% increase, 95% CI 3% decrease to 28% increase; Figure 1C). The 2 regional health authorities with the lowest population rates of frenotomy (1.5 and 1.8 per 1000 live births) had the lowest rates of ankyloglossia (3.8 and 4.6 per 1000 live births) and the lowest rates of frenotomy among cases of ankyloglossia (33.3% and 43.3%). The 2 health authorities with the highest population rates of frenotomy (5.2 and 5.3 per 1000 live births) had high rates of ankyloglossia (7.3 and 8.2 per 1000 live births) and the highest rates of frenotomy among cases of ankyloglossia (63.6% and 72.1%).

## Interpretation

Our study showed that rates of ankyloglossia and frenotomy in British Columbia increased significantly from 2004 to 2013. Nulliparity, obesity, male infant sex and macrosomia were positively associated with ankyloglossia, whereas preterm birth, and twin and higher-order plurality were protective factors. There was a monotonic increase in ankyloglossia rates associated with increasing duration of hospital stay from less than 24 hours to 96-167 hours. Maternal and infant characteristics associated with frenotomy were similar to those associated with ankyloglossia, and there was a two- to threefold variation in regional ankyloglossia and frenotomy rates.

The rate of ankyloglossia in our study (6.6 per 1000 live births) is substantially lower than estimates from previous studies that have typically reported birth prevalence rates of 4% to 10% (range 0.02%-11%).11-16 This underestimation is not surprising, because the anomaly is usually asymptomatic and there is no consensus on the definition and diagnostic criteria for ankyloglossia. Diagnosis of ankyloglossia and other minor congenital anomalies during routine hospital admissions for childbirth is typically sporadic and symptom prompted (i.e., it is especially likely when problems arise with infant feeding). With the recent increased emphasis on breastfeeding initiation before hospital discharge because of the Baby Friendly Hospital Initiative, it is not surprising that ankyloglossia is being diagnosed with increasing frequency.

Our study showed that maternal nulliparity and obesity and infant male sex and macrosomia were positively associated with ankyloglossia, whereas preterm births and births of twins or triplets were negatively associated with ankyloglossia. However, the true association between these factors and ankyloglossia may have been somewhat distorted in our study because of the symptom-prompted nature of the diagnosis. The strength of the association between the risk/protective factors in our study was likely influenced by associations between the above-mentioned factors and breastfeeding difficulties.

There has been a long-standing controversy over the optimal management of infants with ankyloglossia and breastfeeding problems, and this is reflected in contemporary national and international guidelines. The Canadian Paediatric Society's 2011 and 2014 position statements on ankyloglossia state that frenotomy cannot be recommended based on the available evidence.17,18 The Dutch and Japanese pediatric societies19-21 also do not endorse frenotomy, whereas recommendations from the United Kingdom's National Institute for Health and Care Excellence mention both conservative management and early surgical division for cases of ankyloglossia associated with breastfeeding problems.22 UNICEF's Baby Friendly Initiative23 and the American Academy of Pediatrics24 recommend early frenotomy for symptomatic ankyloglossia and describe it as a simple, safe and efficacious procedure. This lack of consensus on the treatment of ankyloglossia arises because of the quality of the evidence on the efficacy of frenotomy. Although several randomized trials have assessed the efficacy of frenotomy for ankyloglossia-associated breastfeeding difficulties,25-29 they were all relatively small studies, with methodologic problems related to inclusion criteria, lack of blinding and subjectively defined outcomes.

The observed increase in the diagnosis of ankyloglossia appears to be a consequence of increased surveillance secondary to the focus on breastfeeding initiation and the Baby Friendly Hospital Initiative. Population rates of frenotomy in British Columbia exhibited a substantial spatial variation by regional health authority, as did rates of frenotomy among cases of ankyloglossia. This is concerning insofar as it reflects arbitrariness with regard to the diagnosis of ankyloglossia and in the use of a potentially unnecessary surgical procedure among newborns. The controversy with regard to the use of frenotomy has been framed as a conflict between lactation nurses, breastfeeding support groups and mothers who have experienced difficulties in breastfeeding versus pediatricians who are focused on the evidence for the efficacy of frenotomy.30 The latter position is also informed by a culture that has increasingly rejected minor surgical intervention (e.g., tonsillectomy, ear tubes) for babies and children with the understanding that most conditions improve spontaneously.

### Strengths and limitations

The strengths of our study included its population-based provenance, the large study size and detailed information on maternal and infant characteristics, diagnoses and procedures. Study limitations included the sporadic and symptom-prompted nature of the diagnosis of ankyloglossia, which likely distorted the birth prevalence. The bias also likely distorted the association between risk/protective factors and ankyloglossia, albeit to a lesser extent. Some transcription errors and missing values with regard to maternal and infant characteristics were also likely, because such deficiencies are inevitable in large population-based databases. Rates of ankyloglossia and frenotomy were estimated among those with missing information and such subjects were included in the regression analysis as a separate category. Other limitations included a lack of detail in our data source regarding the type of anesthesia used for frenotomy and the cost of the procedure. We included frenotomies carried out only in the first few days after birth, since our information was restricted to the birth admission.

### Conclusion

Our study showed a temporal increase in the rate of ankyloglossia and a corresponding increase in the frequency of frenotomy in British Columbia. The wide spatial variation evident in population rates of frenotomy suggests arbitrary differences in practice patterns with regard to such surgery for newborns. Better diagnostic criteria for ankyloglossia, clear indications for frenotomy, improved communication and more detailed clinical practice guidelines are necessary for ensuring that infants with breastfeeding problems due to ankyloglossia are treated appropriately. Surgical treatment for ankyloglossia should be available when indicated, and unnecessary surgery in infancy avoided.

### Supplemental information

For reviewer comments and the original submission of this manuscript, please see [www.cmajopen.ca/content/4/1/E33/suppl/DC1](http://www.cmajopen.ca/content/4/1/E33/suppl/DC1)

## Acknowledgements

K.S. Joseph is supported by the Child and Family Research Institute and by a chair in maternal, fetal and infant health services research from the Canadian Institutes of Health Research (grant no. APR-126338).

## Footnotes

*   Competing interests: None declared.

*   Contributors: K.S. Joseph conceptualized and designed the study and analyzed the data. Brooke Kinniburgh, Amy Metcalfe, Neda Razaz, Yasser Sabr and Sarka Lisonkova contributed to the data analyses. K.S. Joseph drafted the manuscript, and all of the authors revised it critically, gave final approval of the version to be published and agreed to act as guarantors of the work.

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