Keywords
periconception - high-dose folic acid - cleft lip - cleft palate
Introduction
Orofacial cleft is a common congenital anomaly of the craniofacial region—the incidence
being between 1 in 300 live births to 1 in 1,000. A child born with a cleft has to
undergo several surgical procedures over a period of time for correction of the deformities
and in addition to this, there are other hospital visits required for associated issues.
This situation is financially and emotionally draining resulting in significant reduction
in the quality of life of the patients and their family members.[1]
[2] Therefore, prevention of clefts is of utmost importance as a public health issue.
The cascade of processes leading to development of normal lip and palate are intricate,
and prone to disruption at various stages resulting in specific deformities. Orofacial
cleft includes cleft of the lip with or without palate and cleft palate alone. These
two entities have differences in embryonic origin and differences in the recurrence
rates.
The etiology of clefts is linked to genetic and environmental factors. Of the environmental
factors, one which can be easily manipulated is the folic acid link.
A study of susceptibility genes for cleft lip and palate has attempted to correlate
specific gene variants with specific environmental risk factors.[3] Thus, some genetic variants are associated with a background risk which is manifested
when exposed to a particular environmental factor. The genes found to be associated
with folic acid in this way are MTHFR and RFC1.[4]
[5]
[6]
[7]
The recommended dose of folic acid in females of childbearing age for prevention of
neural tube defects is 400 micrograms daily before conception to week 12 of pregnancy.
In those with high risk of neural tube defects, the dose is 5 mg (British National
Formulary). Low doses of folic acid have been shown to prevent neural tube defects
(NTD) and high doses the recurrence of NTD.[8] There is no such evidence based folic acid dose prescribed for oral cleft occurrence
or recurrence. Recurrence which is the occurrence of clefts in members of affected
families is higher by 40 times that of the general population.
There have been several studies reporting the effects of multivitamins containing
folic acid on clefts. Wilcox et al[9] reported reduced risk of isolated cleft lip with or without cleft palate by a third
with folic acid (400 micrograms) supplementation during early pregnancy, but no protection
against cleft palate alone. In a case–control study to determine the association between
nonsyndromic clefts and folic acid, Little et al have concluded that higher intake
of folate does not appear to prevent clefts[10] while a study in Netherlands demonstrated that periconceptional maternal folic acid
supplement was beneficial to reduce the risk for CLP.[11] A Cochrane's review on periconceptional folic acid on a regular dosage[12] showed no evidence of any preventive effects on cleft palate. A recent meta-analysis
by Jahanbin et al[13] have shown that periconceptional multivitamin containing folic acid has a protective
effect on oral clefts.
A cohort-controlled study by Czeizel et al[14] of multivitamin intervention, no significant effect was found for low dose of folic
acid on prevention of oral clefts. But high dose of folic acid (6 mg) was found to
prevent some orofacial clefts.[15] Most studies—case–control and observational—have reported on doses of folic acid
less than 1mg and many have not reported the dose of folic acid used in their studies.
There is a dilemma regarding whether low dose or high dose of folic acid is required
in prevention of orofacial clefts.
A systematic review and meta-analysis by Johnson and Little[16] has shown no strong evidence regarding association between folic acid and oral clefts.
The dosage of folic acid in the various studies ranged from 0.5 to 10 mg and no dose
dependent difference was found in their analysis. But they have concluded that multivitamins
in early pregnancy may have a protective effect on clefts, especially CL ± CP.
We postulate that a high dose of folic acid in the periconceptional period is required
to reduce the occurrence and recurrence of isolated nonsyndromic cleft.
Methods
Protocol was registered on the PROSPERO register of systematic reviews (CRD 42018090927).
PRISMA-P guidelines for the conduct of systematic review and meta-analysis protocol
were followed.
Search Strategy
The following electronic databases were searched:
-
Cochrane, Medline, EMBASE, LILACS BIREME (Latin American and Caribbean Health Science
Information database).
-
Ongoing trials: World Health Organization International Clinical Trials Registry Platform,
U.S. National Institutes of Health Ongoing Trials Register.
-
The metaRegister of Controlled Trials.
-
The US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov.
-
The Australian New Zealand Clinical Trials Registry.
-
The World Health Organization International Clinical Trials Registry Platform.
-
The EU Clinical Trials Register.
There were no restrictions in the search with regards to language, study setting,
or date of publication.
Study Selection
Studies were selected based on the following criteria: human studies assessing the
effectiveness of administration of high-dose folic acid in prevention of nonsyndromic
cleft lip with or without cleft palate (CL ± CP) and cleft palate (CP) were included.
Studies that did not meet the inclusion criteria, review articles, case reports, editorials,
and letters were excluded.
The population of interest was females of reproductive age group who were at high-risk
of having a child with nonsyndromic CL ± CP or isolated CP.
A three stage review process was followed. During the initial stage the titles were
reviewed by two reviewers and the articles not relevant to the review were excluded.
In the second stage, the abstracts of the selected articles were reviewed against
the inclusion criteria ([Fig. 1]: PRISMA-P flow diagram). The final stage consisted of detailed review of the full
texts selected by both reviewers. Discrepancies that arose were dealt with by discussion.
Fig. 1 Study selection PRISMA-P flow diagram.
Data Extraction
We designed data extraction forms to record authorship, year of publication, and details
of study based on inclusion criteria. Two review authors extracted data independently.
The following details were recorded when available.
-
Trial methods: method of randomization, allocation, sample size, blinding methods,
and losses at follow-up.
-
Participants: country of origin, year of study, setting, sample size, inclusion, and
exclusion criteria.
-
Intervention: dosage of folic acid supplemented and duration of supplementation.
-
Control: no supplementation or low-dose folic acid supplementation.
-
Outcomes: Occurrence or recurrence of CL ±CP or isolated CP.
In instances where there is more than one study from the same population by the same
team of researchers, the more recent and relevant study has been included.
Dealing with Missing Data
In trials with missing data, we contacted the principal investigator by electronic
mail.
Data Synthesis
Assessment of Risk of Bias
The assessment of the risks of bias was done using Cochrane's tool for assessing risk
of bias as described in section 8.5 of the Cochrane Handbook for Systematic Reviews
of Interventions. Two reviewers independently performed the assessment and any disagreements
were resolved through discussion with the third reviewer.
Assessment of risk of bias performed for the RCT is as follows.
Sequence Generation
Generation of the randomization sequence was done using permuted blocks of random
size—low risk of bias.
Allocation
Allocation concealment present—low risk of bias.
Blinding
Double blinding done—subjects, investigators, and researchers were blinded to randomization
assignment—low risk of bias.
Incomplete Outcomes Data
Attrition and exclusions and the reasons for these have been reported. The changes
in the recruitment such as reducing the length of participation and including isolated
cleft palate early in the study and not later have all been mentioned in the publication—low
risk of bias.
Selective Outcome Reporting
A study protocol has been published. The inclusion criteria in the protocol mentioned
all cases of nonsyndromic cleft lip with or without cleft palate, both unilateral
and bilateral, excluding cases with recognized syndromes and cleft palate only. In
the overall analysis of outcome results these are included. But results after exclusion
are also provided—low risk of bias.
Other Bias
As a clear study protocol has been published and all variations from the protocol
and study period are stated in the article no other bias was detected.
Results
The study selection PRISMA-P flow diagram is given in [Fig. 1]. The search yielded 401 articles, out of which four studies were selected based
on the inclusion criteria—a single RCT,[17] two prospective case–control trials,[18]
[19] and a single case–control surveillance—Hungarian Case–Control Surveillance of Congenital
Abnormalities[15]
[20] on effect of periconceptional high-dose folic acid on prevention of isolated nonsyndromic
clefts. The three case–control studies were on the prevention of recurrence of clefts,
while the HCCSCA was on congenital abnormalities in general, and with clefts, was
regarding occurrence rather than recurrence of clefts.
CL with or without CP was used as an inclusion criterion for two of the studies, but
in effect only one study (Tolarova and Harris) has reported only on CL ± CP. All others
have included isolated CP also in the analysis. [Table 1] shows analysis of the results of the three case–control studies.
Table 1
Study characteristics of case–control trials
|
Studies
|
Wehby (2013)
|
Tolarova and Harris (1995)
|
Briggs (1976; continuation of peer study)
|
|
Abbreviations: CL, cleft palate; CP, cleft lip.
|
|
Type of study
|
Randomized double blind control trial
|
Nonrandomized prospective case–control
|
Prospective case–control study
|
|
Year
|
2004–2009
|
1976–1992
|
1958–1976
|
|
Study location
|
Six craniofacial clinics in Brazil
|
Department of Medical Genetics of the Czechoslovak Academy of Sciences, Prague
|
Saint Barnabas Medical Center, Livingston, New Jersey
|
|
Type of cleft
|
Isolated oral cleft recurrence (CL ± CP and CP)
|
Recurrence of oral cleft (CL ± CP)
|
Recurrence of oral cleft (CL ± CP and CP)
|
|
Number of patients in study population
|
1,257
|
221 pregnancies at risk of child with cleft
|
228 pregnant mother at risk of child with cleft
|
|
Dose of folic acid in study population
|
4 mg
|
10 mg
|
5 mg
|
|
Number of controls
|
1,251
|
1,901 pregnant women at risk of child with cleft
|
417 pregnant mother at risk of child with cleft
|
|
Dose of folic acid in controls
|
0.4 mg
|
Nil
|
Nil
|
|
Time of administration
|
Before planned conception and continued up to first trimester
|
2 months before planned conception and continued up to 3 months
|
Before planned conception and continued up to 5th month of pregnancy
|
|
Cleft cases in study population
|
3 cases
CL = 1
CP = 1
CL + CP = 1
|
3 out of 214 informative pregnancies
|
7 cases
CL + CP = 3
CP = 3
|
|
Cleft cases in controls
|
3 cases of CL + CP
|
77 out of 1,901 Informative pregnancies
|
20 cases
CL + CP = 15
CP = 5
|
|
Method of statistical analysis used
|
Fischer's exact test and Student t-test
|
Chi-square and Fischer's exact test
|
Not mentioned
|
|
Recurrence risks
|
Oral cleft recurrence was 2.9% in 0.4 mg group and 0.8% in 4 mg group (CP excluded)
|
65% decrease in cleft recurrence found in supplemental group
|
Incidence rate in study group for both CL ± CP and CP was lower than the control group
(3.1% vs. 4.8%)
|
|
Adverse effects
|
Nil
|
Nil
|
Nil
|
|
Additional comments
|
Oral cleft recurrence was 2.9% in 0.4 mg group and 1.6% in 4 mg group when both CL
± CP and CP included.
Recurrence rate was similar between the two groups
|
Best efficacy of supplementation was found in the subset with unilateral cleft (3.51%
vs. 0.6%), a decrease by 82.6%.
No difference in the subgroup of female probands with bilateral cleft
|
Incidence of 1.9% in the treated group for CL + CP (1.9% vs. 5.5%).
Incidence of 6% in the treated group for CP (6% vs. 3.5%)
|
Czeizel et al had conducted two interventional studies earlier and the low dose of
folic acid in the multivitamin supplemented was reported to be ineffective in preventing
clefts. The HCCSCA ([Fig. 2]) like the other two studies was on several congenital anomalies of which cleft was
one. Use of high-dose folic acid is reported to bring about some reduction in both
CL ±CP and CP.
Fig. 2 Hungarian Study flow chart.
We came across a study protocol of a community based randomized clinical trial on
effect of high-dose folic acid on prevention of congenital malformations in Italy
and Netherlands.[21] Contacting the principal investigator by electronic mail revealed that the analysis
of the trial is still ongoing.
Discussion
The double blinded randomized control trial (RCT) by Wehby et al[17] on the effect of periconceptional folic acid on prevention of recurrence of isolated
cleft was conducted during the period 2004 to 2009. This involved 2,508 females and
the dose of folic acid given to the study population was 4 mg while the controls received
the usual dose present in a multivitamin which is 0.4 mg. The outcome was based on
234 live births. The recurrence rates for oral clefts were found to be similar between
the two groups (2.9% in the 0.4 mg and 2.5% in the 4 mg group) when cases of cleft
lip with or without cleft palate as well as isolated cleft palate in the study groups
were included. This shows a wide difference from the historic recurrence rate postfolic
acid fortification (6.3%; p = 0.0009 when both folic acid groups are combined). But isolated cleft palate was
not in the inclusion criteria of the study and excluding this, the recurrence rate
is 1.6%. Apart from this, one of the cases was diagnosed as Van-der-Woude's syndrome
(VWS), and hence excluded, as this is the most common syndromic form of oral cleft
with a 50% recurrence risk. The recurrence rate was significantly low in 4 mg group
when cleft lip with palate alone was considered (0.8%), while this was 2.9% in the
0.4 mg group.
The researchers have concluded that the small sample limits their ability to arrive
at a formal statistical inference to compare the effect of high- and low-dose folic
acid on cleft recurrence.
No compromise in fetal growth was observed in any of the groups.
The Hungarian Case–Control Surveillance of Congenital Abnormalities from 1980 to 1996
regarding high-dose folic acid in the periconceptional period was a study on various
congenital anomalies. Clefts was not the outcome of primary interest, it was only
one of the outcomes being evaluated and included isolated cleft lip with or without
cleft palate.
The cases were obtained from the Hungarian Congenital Abnormality Registry (HCAR)
and consisted of 22,843 malformed offspring and control group from the National Birth
Registry consisting of 38,151 cases.
The dose of folic acid was not recorded in 50% of the pregnant women. But in the validation
study based on 600 pregnant women, the dose of folic acid used was found to be 3 mg
in 22.5%, 6 mg in 68.6%, and 9 mg in 8.9%. There were 1,374 cases of CL ± CP and 601cases
of CP.
Though the multivitamin with low dose (0.8 mg) of folic acid in the intervention trials[14] by Czeizel et al did not show reduction in orofacial clefts, the high dose in the
HCCSCA demonstrated some preventive effect on clefts especially cleft palate.
The nonrandomized case–control study by Tolarova and Harris was specifically on recurrence
of nonsyndromic isolated CL ±CP. 221 pregnancies in females at risk of CL ±CP were
the study population. They were given multivitamin with 10 mg folic acid from at least
2 months before conception to 3 months after. The control group consisted of 1,901
females at risk of CL ±CP with no supplementation. The incidence was 1.4 and 4.05%
in the supplemented and control groups respectively, indicating a risk reduction of
65.4%. Best results were found with unilateral cleft (3.5 vs. 0.61%), a decrease by
82.6%.
No difference was found in female probands with bilateral cleft.
Publication by Briggs[19] is a continuation of the Peer et al[22] study, as a prospective case–control study on effect of 5 mg of folic acid during
the periconceptional period on recurrence of oral clefts.
The incidence in the pregnancy after having had a child with isolated cleft and subsequent
pregnancies are available separately. The study group consisted of 228 women with
previous cleft children who were supplemented with vitamins and the control group
417 women with previous clefts who were not supplemented. Of the 228, 161 had children
with CL ± CP and the recurrence was 3 (1.9%). There were 67 with cleft palate alone
and the recurrence was 4 (6%), a total recurrence rate of 3.1%. The incidence in the
control group was 5.5%, 3.5%, and 4.8% for CL ±CP, CP alone, and total respectively.
The figures show an impressive effect when the deformities are taken separately in
that there is a significant reduction in CL ± CP in the supplemented group. The recurrence
rate for CP alone is considerably high. There is an overall reduction in recurrence
of 1.7% when compared with the unsupplemented group.
The dose of folic acid in the high dose studies varied widely. The inclusion criteria,
study target as in CL ± CP and isolated CP, method of supplementing folic acid—alone
or in combination with other vitamins, and variations in control group management
as in no folic acid or low-dose folic acid are some of the heterogeneities when comparing
the four studies. Due to the various heterogeneities in the studies a meta-analysis
is not justifiable.
Of the four studies available to date, the most recent one itself is almost 10 years
and the other three more than 25 years, demonstrating the paucity of such studies
in current times.
The studies were conducted in Europe, United States, and South America. There are
none from Asian or African countries. Since the incidence of cleft is maximum in Asian
countries, absence of studies from this continent is a significant drawback.
Conclusions
There are several gaps in the evidence regarding the efficacy of high-dose folic acid
in prevention of oral clefts. From the data obtained from the available studies (Level
1b evidence for the RCT and Level 3b evidence for the case–control studies based on
Oxford Centre for Evidence-based Medicine Levels of Evidence), there does seem to
be a strong association between high-dose folic acid administration and prevention
of isolated CL ±CP. With regard to isolated CP, the link appears to be very weak.
The fact that these two entities are etiologically different could be the reason for
the difference in behavior.
None of the studies have reported any adverse side effects from supplementation of
high-dose folic acid during the periconceptional period.
Considering the high-cost related to management of cleft cases and psychological and
social burden associated, it might be justifiable to supplement high-dose folic acid
during periconceptional period to high risk females to prevent recurrence of clefts.
Multicenter randomized controlled trials in different continents with large number
of cases and controls assessing the efficacy of specifically high-dose folic acid
rather than multivitamins containing folic acid in prevention of occurrence and recurrence
of orofacial clefts are required. The dose of folic acid for the recurrence prevention
studies need to be standardized to 5 mg as done for neural tube defects. It might
be prudent to conduct numerous trials in Asian countries like India as numbers are
easily achievable due to the very high incidence rates of cleft in this continent.
The studies should be done separately on CL ±CP and isolated CP as there is a significant
difference in behavior in response to folic acid supplementation from studies so far.
Protocol Registered with PROSPERO
(International prospective register of systematic reviews). Registration number: CRD42018090927.
