Little is known about the epidemiologic features of syndactyly (SD) in Chinese newborns.
Methods
Using 2007–2019 data from the Chinese Birth Defects Monitoring Network, we conducted a prevalence analysis on overall, isolated and associated syndactyly according to birth year, maternal age, maternal residence, geographic region and infant sex, with special interests in time trends, perinatal outcomes and clinical phenotypes.
Results
A total of 13,611 SD cases were identified among 24,157,719 births in the study period, yielding the prevalence of 5.63, 4.66 and 0.97 per 10,000 for overall, isolated, and associated SD, respectively. The prevalence of each type of SD exhibited an upward trend over the period. The prevalence of overall SD varied significantly by maternal residence (urban vs. rural, 6.69/10,000 vs. 4.35/10,000), maternal age (< 20 years, 5.43/10,000; 20–24 years, 5.03/10,000; 25–29 year, 5.65/10,000; 30–34 years, 6.07/10,000; ≥ 35 years, 5.76/10,000), geographic region (central, 5.07/10,000; east, 6.75/10,000; west, 5.12/10,000), and infant sex (male vs. female, 6.28/10,000 vs. 4.86/10,000). Newborns with associated SD were more likely to be born prematurely (29.2% vs. 10.6%) or with low birthweight (30.5% vs.9.8%) than those with isolated SD. The bilaterally, and unilaterally affected cases accounted for 18.4% and 76.7%, respectively. The feet were more frequently involved (64.3%) in those bilaterally affected cases, while right side preference (right vs left: 53.8% vs 46.2%) and upper limbs preference (hand vs foot: 50.8% vs 48.0%) were found in unilateral cases.
Conclusions
The prevalence of syndactyly in China is on the rise and notably higher than that in other Asian and European countries, highlighting the importance of investigating the etiology, epidemiology, and clinical implications of this condition in the Chinese population.
Hinweise
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Introduction
Syndactyly (SD) is one common limb malformation characterized by soft tissue and/or osseous fusion of adjacent digits in either the upper or lower extremities, resulting from the embryological failure of phalanges to separate during limbs development [1]. Clinically, SD may affect one or more limbs, being a familial or sporadic, a symmetrical or asymmetrical condition. This malformation can be further categorized into ten subtypes depending on its genotype–phenotype features [2]. In epidemiological studies, SD cases are usually classified into non-syndromic (isolated) or syndromic forms (associated) [3]. The prevalence of syndactyly ranges from 0.90 to 7.40 per 10,000 live births, varying by sex, geographic region, and ethnic groups [4‐7].
The information on prevalence, phenotypes and outcome of SD is of great significance both from epidemiological and clinical perspectives. Although syndactyly has a strong genetic component, a growing body of evidence suggests that socioeconomic and environmental factors play a role in the occurrence of SD [8]. China’s economy, environment, maternal and child health have changed greatly in recent two decades [9]. Several studies using provincial or local hospital-based surveillance data have shown wide variability in SD prevalence in China [10, 11], whereas epidemiological studies based on national data are rare. To gain new insights into the epidemiology of syndactyly, we performed a prevalence study on syndactyly in Chinese newborns, with special interests in time trends and the involved limbs, using data from the Chinese Birth Defects Monitoring Network (CBDMN) from 2007 to 2019.
Anzeige
Materials and methods
Study subjects
The CBDMN is a nationwide hospital-based birth defects surveillance program established in 1986. It covers a total of 780 member hospitals in 31 provinces, municipalities, or autonomous regions. The program monitors approximately 10% of the annual births in China [12]. It collects information on perinatal infants with or without anogenital anomalies (live or still births aged 28 weeks of gestation or more) born in member hospitals. The process of data collection, case identification, and quality control have been described elsewhere [12]. Diagnosis of SD was usually made by obstetricians or pediatricians at member hospitals by physical examination and radiography. All anomalies in the CBDMN database were coded by trained professionals according to the International Classification of Disease version 10 (ICD10). The current study distinguished isolated SD cases with only Q70 code from associated SD cases with Q70 and other codes for extra anomalies.
The prevalence rate was defined as the number of SD cases per 10,000 births. We compared the differences in prevalence based on birth year, maternal residence, maternal age, geographic region, and infant sex. The classification of residential areas as urban or rural depended on the mother’s last residence for at least one year. Maternal age was categorized into five age groups: < 20 years, 20–24 years, 25–29 years, 30–34 years and ≥ 35 years. Geographic regions were divided into the eastern, western, and central according to geographic location and economic level [13]. We compared the differences in percentages between isolated and associated cases based on gestational age, birth weight, perinatal outcome, nationality, singleton, parity, family history, laterality, and symmetry of syndactyly cases.
Statistical analysis
The prevalence rates and their 95% confidence intervals (95% CI) were estimated based on Poisson distribution. Multivariate Poisson regression analysis was used to calculate the adjusted prevalence rate ratios (aPRR) and their 95% CIs. When computing the aPRR by one of these factors (birth year, maternal residence, maternal age, geographic region, and infant sex), we controlled the effects of the others. Time trends in prevalence over the study period were analyzed using the Joinpoint regression program (version 4.9.0.1, Statistical Research and Applications Branch, National Cancer Institute, Bethesda, MD, USA) [14]. The changes of prevalence for overall, isolated and associated were presented as the average annual percentage change (APC). Chi-square test was used to examine differences in percentages between isolated and associated cases based on characteristics, perinatal outcomes and the involved limbs. Data analysis was performed using R version 4.0.2 (the Comprehensive R Archive Network: http://cran.r-project.org). The significance level for α was set at 0.05.
Results
Table 1 shows the SD prevalence rates stratified by birth year, maternal residence, maternal age, geographic region, and infant sex. In the period of 2007–2019, a total of 13,611 syndactyly cases were identified among 24,157,719 newborns, giving the prevalence of 5.63 (95%CI: 5.54–5.73), 4.66 (95%CI:4.58–4.75) and 0.97 (95%CI:0.93–1.01) per 10,000 births for the overall, isolated, and associated syndactyly, respectively. Multivariate Poisson regression analysis confirmed the significant variations in prevalence by urban–rural areas, maternal age, geographic region, and infant sex. Moreover, both isolated and associated prevalence presented similar sociodemographic patterns (Table 1). Urban prevalence rates were significantly higher than rural rates (urban vs rural: overall, 6.69/10,000 vs 4.35/10,000; isolated, 5.64/10,000 vs 3.49/10,000; associated, 1.06/10,000 vs 0.86/10,000). A U-shaped pattern was found for maternal age-specific prevalence rates of overall, isolated, and associated SD, with higher rates in the maternal age group of 30–34 years and lower rates in the group of 20–24 years for overall and isolated while higher rates in the ≥ 35 years age group and lower rates in the 20–24 years group for associated SD. All the prevalence of overall, isolated, and associated SDs presented significant geographic variations. The highest rates were usually found in the eastern region, followed by the rates in the western or central regions. Considerable male predominance in prevalence was observed for syndactyly (male vs female: overall, 6.28/10,000 vs 4.86/10,000; isolated, 5.21/10,000 vs 4.05/10,000; associated,1.08/10,000 vs 0.81/10,000).
Table 1
Prevalence rates of syndactyly stratified by birth year, maternal residence, maternal age, geographic region, and infant sex (per 10,000 births) a, c
Characteristics
Number of births
Overall SD
Isolated SD
Associated SD
Cases (n)
Prevalence (95%CI)
aPRR(95%CI)
Cases (n)
Prevalence (95%CI)
aPRR(95%CI)
Cases (n)
Prevalence (95%CI)
aPRR(95%CI)
Birth year
2007
1,258,298
533
4.24(3.88–4.61)
1.00(reference)
442
3.51(3.19–3.86)
1.00(reference)
91
0.72(0.58–0.89)
1.00(reference)
2008
1,314,091
591
4.50(4.14–4.88)
1.08(0.90–1.28)
486
3.70(3.38–4.04)
1.14(0.94–1.38)
105
0.80(0.65–0.97)
0.80(0.52–1.22)
2009
1,401,331
647
4.62(4.27–4.99)
1.15(0.97–1.36)
522
3.73(3.41–4.06)
1.17(0.96–1.41)
125
0.89(0.74–1.06)
1.08(0.73–1.60)
2010
1,531,143
723
4.72(4.38–5.08)
1.11(0.94–1.31)
587
3.83(3.53–4.16)
1.09(0.90–1.32)
136
0.89(0.75–1.05)
1.19(0.82–1.74)
2011
1,681,096
835
4.97(4.64–5.32)
1.18(1.01–1.39)
668
3.97(3.68–4.29)
1.20(1.00–1.44)
167
0.99(0.85–1.16)
1.11(0.76–1.62)
2012
2,005,526
886
4.42(4.13–4.72)
1.02(0.86–1.19)
749
3.73(3.47–4.01)
1.08(0.91–1.29)
137
0.68(0.57–0.81)
0.73(0.49–1.09)
2013
1,893,560
963
5.09(4.77–5.42)
1.20(1.02–1.40)
807
4.26(3.97–4.57)
1.22(1.03–1.46)
156
0.82(0.70–0.96)
1.08(0.75–1.56)
2014
2,198,802
1137
5.17(4.87–5.48)
1.18(1.02–1.38)
938
4.27(4.00–4.55)
1.20(1.02–1.43)
199
0.91(0.78–1.04)
1.09(0.77–1.56)
2015
1,883,843
1070
5.68(5.34–6.03)
1.39(1.19–1.62)
875
4.64(4.34–4.96)
1.45(1.22–1.72)
195
1.04(0.89–1.19)
1.12(0.78–1.62)
2016
2,432,979
1416
5.82(5.52–6.13)
1.33(1.15–1.54)
1143
4.70(4.43–4.98)
1.35(1.15–1.59)
273
1.12(0.99–1.26)
1.25(0.88–1.75)
2017
2,315,621
1565
6.76(6.43–7.10)
1.57(1.36–1.82)
1316
5.68(5.38–6.00)
1.69(1.43–1.98)
249
1.08(0.95–1.22)
1.11(0.77–1.58)
2018
2,097,800
1595
7.60(7.23–7.99)
1.77(1.52–2.05)
1350
6.44(6.10–6.79)
1.88(1.60–2.21)
245
1.17(1.03–1.32)
1.29(0.90–1.84)
2019
2,143,629
1641
7.66(7.29–8.03)
1.78(1.54–2.06)
1380
6.44(6.10–6.79)
1.87(1.59–2.20)
261
1.22(1.07–1.37)
1.39(0.98–1.97)
Total
24,157,719
13,062
5.63(5.54–5.73)
—
11,263
4.66(4.58–4.75)
—
2339
0.97(0.93–1.01)
—
Maternal residence
Urban
13,184,029
8823
6.69(6.55–6.83)
1.48(1.43–1.54)
7432
5.64(5.51–5.77)
1.55(1.49–1.62)
1391
1.06(1.00–1.11)
1.18(1.09–1.29)
Rural
10,973,690
4779
4.35(4.23–4.48)
1.00(reference)
3831
3.49(3.38–3.60)
1.00(reference)
948
0.86(0.81–0.92)
1.00(reference)
Maternal age
< 20
503,201
273
5.43(4.80–6.11)
0.68(0.25–1.83)
218
4.33(3.78–4.95)
0.65(0.21–2.03)
55
1.09(0.82–1.42)
0.79(0.11–5.76)
20–24
5,015,671
2521
5.03(4.83–5.23)
0.88(0.70–1.10)
2068
4.12(3.95–4.30)
0.95(0.74–1.21)
453
0.90(0.82–0.99)
0.58(0.32–1.04)
25–29
10,074,580
5690
5.65(5.50–5.80)
1.00(reference)
4770
4.73(4.60–4.87)
1.00(reference)
920
0.91(0.86–0.97)
1.00(reference)
30–34
5,864,829
3562
6.07(5.88–6.28)
1.02(0.82–1.27)
2978
5.08(4.90–5.26)
1.06(0.83–1.35)
584
1.00(0.92–1.08)
0.84(0.49–1.43)
≥ 35
2,699,438
1556
5.76(5.48–6.06)
1.17(0.87–1.57)
1229
4.55(4.30–4.81)
1.21(0.87–1.68)
327
1.21(1.08–1.35)
0.99(0.48–2.01)
Geographic region
Central
8,966,230
4543
5.07(4.92–5.22)
1.00(reference)
3797
4.23(4.10–4.37)
1.00(reference)
746
0.83(0.77–0.89)
1.00(reference)
East
7,820,462
5282
6.75(6.57–6.94)
1.29(1.24–1.34)
4362
5.58(5.41–5.75)
1.27(1.21–1.32)
920
1.18(1.10–1.25)
1.40(1.27–1.54)
West
7,371,027
3777
5.12(4.96–5.29)
0.99(0.95–1.03)
3104
4.21(4.06–4.36)
0.98(0.93–1.02)
673
0.91(0.85–0.98)
1.08(0.97–1.20)
Infant sexb
Male
12,774,073
8028
6.28(6.15–6.42)
1.29(1.25–1.34)
6650
5.21(5.08–5.33)
1.29(1.24–1.34)
1378
1.08(1.02–1.14)
1.33(1.22–1.44)
Female
11,378,966
5535
4.86(4.74–4.99)
1.00(reference)
4609
4.05(3.93–4.17)
1.00(reference)
926
0.81(0.76–0.87)
1.00(reference)
a 9 cases with unknown gender were excluded
b 39 cases and 4680 perinatal infants with unspecified gender were excluded
c In addition to the variables listed above, we included an interaction term between year and maternal age group in the model to control for potential confounding from temporal variations related to maternal age
Anzeige
The annual prevalence rates of syndactyly were on the rise from 2007 through 2019 (Table 1 and Fig. 1), increasing from 4.24/10,000 to 7.66/10,000, from 3.51/10,000 to 6.44/10,000, and from 0.72/10,000 to 1.22/10,000 for the overall, isolated, and associated syndactyly, respectively. The overall prevalence rate was on a stabilization upward trend with an APC of 2.4% for the 2007–2014 period, followed by a significant increase during the period from 2014–2019, by 9.2%. The prevalence of isolated cases kept almost the same rising trend as overall cases, with an APC of 2.4% from 2007 to 2014 and an APC of 9.7% from 2014 to 2019. The prevalence rate of associated SD was slightly on an upward trend with an APC of 3.9% from 2007 to 2019.
×
Table 2 shows the basic characteristics and perinatal outcomes of SD cases in the current study. Preterm births accounted for 13.8% of overall SD cases, and more associated SDs were born prematurely than isolated cases (29.2% vs. 10.6%). Totally, 13.4% of SD cases were born with low birth weight (LBW). The LBW rate of associated SD (30.5%) was significantly higher than that of isolated SD (9.8%). Perinatal mortality of SD cases was 4.1%, and infants with associated SD were at a higher risk of perinatal death (16.4%) compared with those affected by isolated SD (1.4%). Both the stillbirth rate (intrauterine death, spontaneous abortion, and termination of pregnancy due to antenatally diagnosed birth defects) and early neonatal mortality rate of associated SD (12.2% and 4.4%) were 10 more times higher than those of isolated cases (1.0% and 0.4%). Among the cases, 92.7% were Han Chinese, and the rest were ethnic minorities. Majority of SD cases were singletons (95.8%), and the rest were twins or multiple-births (4.2%). About two-thirds of the affected children were born to primiparas women. More infants with associated SD (35.7%) were born to multiparous women compared with isolated SD (34.9%). Notably, only 2.8% of affected infants had a family history, and 97.2% were sporadic cases.
Table 2
Characteristics and perinatal outcomes of syndactyly cases in Chinese newborns
Characteristics
Overall
(N = 13,611)
Isolated
(N = 11,268)
Associated
(N = 2343)
Gestational age(weeks) b
< 37
1880 (13.8%)
1196 (10.6%)
684 (29.2%)
37-
11,631 (85.5%)
9989 (88.6%)
1642 (70.1%)
≥ 42
100 (0.7%)
83 (0.7%)
17 (0.7%)
Birth weight(g) b
< 1500
300 (2.2%)
129 (1.1%)
171 (7.3%)
1500-
1522 (11.2%)
978 (8.7%)
544 (23.2%)
2500-
10,948 (80.4%)
9435 (83.7%)
1513 (64.6%)
≥ 4000
841 (6.2%)
726 (6.4%)
115 (4.9%)
Perinatal outcomea, b
Stillbirths
403 (3.0%)
117 (1.0%)
286 (12.2%)
Neonate death within 7 days
143 (1.1%)
40 (0.4%)
103 (4.4%)
Live within perinatal period
13,061 (96.0%)
11,110 (98.6%)
1951 (83.3%)
Nationalityb
Han
12,620 (92.7%)
10,483 (93.0%)
2137 (91.2%)
Minorities
991 (7.3%)
785 (7.0%)
206 (8.8%)
Singletonb
Yes
13,036 (95.8%)
10,822 (96.0%)
2214 (94.5%)
No
575 (4.2%)
446 (4.0%)
129 (5.5%)
Parityb
1
8843 (65.0%)
7337 (65.1%)
1506 (64.3%)
≥ 2
4768 (35.0%)
3931 (34.9%)
837 (35.7%)
Family historyb
Yes
377 (2.8%)
319 (2.8%)
58 (2.5%)
No
13,234 (97.2%)
10,949 (97.2%)
2285 (97.5%)
a 4 cases with unknown perinatal outcome were excluded
b Differed significantly between isolated and associated
We further analyzed the laterality and limb involvements of SD cases. As shown in Table 3, the bilaterally, and unilaterally affected cases accounted for 18.4% and 76.7%, respectively. In those bilaterally affected cases, the feet were more frequently involved (64.3%), and lower limbs involvements were more common in associated SD compared with isolated cases (30.1% vs 17.4%). In unilateral cases, right side preference (right vs left: 53.8% vs 46.2%) and upper limbs preference (hand vs foot: 50.8% vs 48.0%) were found, with more feet involvements in unilateral isolated cases (51.0%) but more hands involvements (62.0%) in unilateral associated SD.
Table 3
Laterality and symmetry in Chinese syndactyly
Characteristicsb
Overall
(N = 13,611)
Isolated
(N = 11,268)
Associated
(N = 2343)
Bilateral (n = 2500) c
2502 (18.4%)
1924 (17.1%)
578 (24.7%)
Hand
893 (35.7%)
663 (34.5%)
230 (39.8%)
Foot
1100 (44.0%)
926 (48.1%)
174 (30.1%)
Hand and foot a
509 (20.3%)
335 (17.4%)
174 (30.1%)
Unilateral (n = 10,434) d
10,434 (76.7%)
8931 (79.3%)
1503 (64.1%)
Lefte
4819 (46.2%)
4074 (45.6%)
745 (49.6%)
Hand
2458 (51.0%)
2006 (49.2%)
452 (60.7%)
Foot
2295 (47.6%)
2015 (49.5%)
280 (37.6%)
Hand and foot
66 (1.4%)
53 (1.3%)
13 (1.7%)
Righte
5615 (53.8%)
4857 (54.4%)
758 (50.4%)
Hand
2838 (50.5%)
2384 (49.1%)
454 (59.9%)
Foot
2710 (48.3%)
2422 (49.9%)
288 (38.0%)
Hand and foot
67 (1.2%)
51 (1.1%)
16 (2.1%)
Laterality unspecified (n = 677) f
675 (5.0%)
413 (3.7%)
262 (11.2%)
Hand
555 (82.2%)
330 (79.9%)
225 (85.9%)
Foot
52 (7.7%)
39 (9.4%)
13 (5.0%)
Hand and foot
19 (2.8%)
7 (1.7%)
12 (4.6%)
Limb unspecified
49 (7.3%)
37 (9.0%)
12 (4.6%)
a Included 7 types: left hand + right foot, left foot + right hand, left hand + right hand + left foot, left hand + right hand + right foot, left hand + left foot + right foot, right hand + left foot + right foot, left hand + right hand + left foot + right foot
b Differed significantly between isolated and associated when divided by bilateral, unilateral and laterality unspecified
c Differed significantly between isolated and associated when divided by hand, foot, hand and foot in bilateral group
d Differed significantly between isolated and associated when divided by left, right in unilateral group
e Differed significantly between isolated and associated when divided by hand, foot, hand and foot in left group and right group
f Differed significantly between isolated and associated when divided by hand, foot, hand and foot, limb unspecified in laterality unspecified group
As shown in Table 4, a total of 2343 cases (17.2%) were accompanied by additional chromosomal or structural malformations. The most common congenital anomalies seen in associated SD cases by system included musculoskeletal system anomalies (69.9%) and circulatory system malformations (13.6%). Specifically, polydactyly was the most common additional deformity, accounted for 27.6% of total coexisting anomalies mentioned above, followed by reduction defects of upper limb (22.5%). SD cases rarely occurred with anomalies of respiratory system (0.6%), urinary system (1.9%) and chromosomal abnormalities (2.0%).
Table 4
Abnormalities associated with syndactyly
System/ Abnormalities
ICD-10 code
N
Percent
Nervous system
Q00-Q07
116
4.95
Anencephaly
Q00
11
0.47
Encephalocele
Q01
11
0.47
Microcephaly
Q02
3
0.13
Hydrocephalus
Q03
56
2.39
Other malformations of brain
Q04
29
1.24
Spina bifida
Q05
14
0.60
Other malformations of nervous system
Q07
1
0.04
Eye, ear, face and neck
Q10-Q18
175
7.47
Congenital malformations of eyelid, lacrimal apparatus, and orbit
Q10
4
0.17
Anophthalmos, microphthalmos, and macrophthalmos
Q11
5
0.21
Congenital lens malformations
Q12
1
0.04
Congenital malformations of anterior segment of eye
Q13
1
0.04
Other congenital malformations of eye
Q15
7
0.30
Congenital malformations of ear causing impairment of hearing
Q16
14
0.60
Malformations of ear
Q17
131
5.59
Malformations of face and neck
Q18
16
0.68
Circulatory system
Q20-Q28
318
13.57
Malformations of cardiac chambers and connections
Q20
11
0.47
Malformations of cardiac septa
Q21
223
9.52
Congenital malformations of pulmonary and tricuspid valves
Q22
18
0.77
Congenital malformations of aortic and mitral valves
Q23
4
0.17
Other congenital malformations of heart
Q24
30
1.28
Congenital malformations of great arteries
Q25
126
5.38
Congenital malformations of great veins
Q26
15
0.64
Other congenital malformations of peripheral vascular system
Q27
14
0.60
Respiratory system
Q30-Q34
15
0.64
Congenital malformations of nose
Q30
10
0.43
Congenital malformations of larynx
Q31
2
0.09
Congenital malformations of lung
Q33
3
0.13
Cleft lip and cleft palate
Q35-Q37
199
8.49
Cleft palate
Q35
63
2.69
Cleft lip
Q36
47
2.01
Cleft palate with cleft lip
Q37
89
3.80
Digestive system
Q38-Q45
101
4.31
Other congenital malformations of tongue, mouth and pharynx
Q38
6
0.26
Congenital malformations of esophagus
Q39
15
0.64
Other congenital malformations of upper alimentary tract
Q40
2
0.09
Congenital absence, atresia and stenosis of small intestine
Q41
3
0.13
Congenital absence, atresia and stenosis of large intestine
Q42
66
2.82
Other congenital malformations of intestine
Q43
6
0.26
Congenital malformations of gallbladder, bile ducts, and liver
Q44
3
0.13
Other congenital malformations of digestive system
Q45
2
0.09
Genital organs
Q50-Q56
140
5.98
Other congenital malformations of female genitalia
Q52
5
0.21
Undescended testicle
Q53
37
1.58
Hypospadias
Q54
52
2.22
Other congenital malformations of male genital organs
Q55
24
1.02
Indeterminate sex and pseudohermaphroditism
Q56
27
1.15
Urinary system
Q60-Q64
45
1.92
Renal agenesis and other reduction defects of kidney
Q60
11
0.47
Cystic kidney disease
Q61
5
0.21
Malformations of renal pelvis and ureter
Q62
17
0.73
Other malformations of kidney
Q63
8
0.34
Other congenital malformations of urinary system
Q64
6
0.26
Musculoskeletal system
Q65-Q79
1638
69.91
Congenital deformities of feet
Q66
204
8.71
Congenital musculoskeletal deformities of head, face, spine, and chest
Q67
9
0.38
Other congenital musculoskeletal deformities
Q68
27
1.15
Polydactyly
Q69
646
27.57
Reduction defects of upper limb
Q71
527
22.49
Reduction defects of lower limb
Q72
324
13.83
Reduction defects of unspecified limb
Q73
40
1.71
Other congenital malformations of limb(s)
Q74
57
2.43
Other congenital malformations of skull and face bones
Q75
18
0.77
Other congenital malformations of spine and bony thorax
Q76
16
0.68
Osteochondrodysplasia with defects of growth of tubular bones and spine
Q77
2
0.09
Other malformations of musculoskeletal system
Q79
42
1.79
Chromosomal abnormalities
Q90-Q99
46
1.96
Down’s syndrome
Q90
33
1.41
Edward‘s syndrome, unspecified
Q91.3
6
0.26
Triploidy and polyploidy
Q92.7
1
0.04
Balanced rearrangements and structural markers, not elsewhere classified
Q95
1
0.04
Other chromosome abnormalities, not elsewhere classified
Q99
5
0.21
Other malformations
Q80-Q89
70
2.99
Congenital ichthyosis
Q80
1
0.04
Other congenital malformations of skin
Q82
12
0.51
Congenital malformations of breast
Q83
2
0.09
Other congenital malformations of integument
Q84
16
0.68
Other specified congenital malformation syndromes affecting multiple systems
Q87
16
0.68
Other congenital malformations, not elsewhere classified
Q89
23
0.98
Other malformations, not coded in Q00-Q99
—
52
2.22
Discussion
This study analyzed data from a large sample of syndactyly (SD) cases in contemporary Chinese population and found that the overall prevalence of SD was 5. 63 per 10,000 live births. This prevalence was lower than those reported in New York State (7.40 per 10,000 live births) [7], Chile (7/10,000) [15], and Hawaii Japanese (6.13/10,000) [16], but higher than those reported in northern Netherlands (4.7/10,000) [17], Italy (0.7/10,000) [18], other European countries (4.86 per 10,000 live births, from 1980 to 2012) [6], and some Asian countries such as Korean (3.09/10,000) [19], and Thai (2.1/10,000) [5]. Notably, the overall SD prevalence in this study was nearly comparable to the rates in Jiangsu and Zhejiang provinces of China that adopted same surveillance approaches and inclusion criteria of SD as CBDMN [10, 11]. The study also found that 17.2% of SD cases were associated with additional major anomalies, which is consistent with previous investigations [20]. Variations in SD prevalence across studies might be due to differences in population, data sources, inclusion criteria, study design, and research duration. High SD prevalence has been noted in Caucasian populations [1, 21]. The findings indicate that the Chinese population is also at a high risk of SD, supporting racial differences in SD prevalence.
Studies conducted in various regions or countries such as New York State [7], Chile [15], Spain [22], Ukraine [22], Korea [19], and several provinces in China [10, 11] have noted an increase in the prevalence of syndactyly over the last two decades. However, some European countries like the United Kingdom, Italy, and Belgium have shown a slight decline in SD prevalence [22]. The underlying causes for such changes in SD prevalence are unclear. Genetic variants such as mutations in HOXD13, FBLN1, LMBR1, FGFR2, BHLHA9, GLI3, and chromosomal aberrations can contribute to the development of SD [23, 24]. Recent studies indicate a positive association between maternal exposure to smoking, medication, and ambient air pollutants and offspring SD [25‐28]. Animal models suggest that the normal development of digits depends on precise regulation and interactions between multiple genetic pathways such as the SHH, WNT signaling pathway [29]. The SD prevalence data obtained in this study is relatively reliable, as the CBDMN system is stable and undergoes strict multi-level quality control annually. The increasing prevalence of SD in China and other places may be attributed to gene mutations related to environmental exposure or disruptions in genetic pathways in limb development.
Male excess in SD prevalence for isolated and associated SD suggested that male embryos might be more susceptible to SD [30], which is consistent with previous epidemiological studies and case reports [1, 7, 30]. The reason for distorted sex ratio in SD cases remains unknown. Significant urban–rural, geographic differences were also identified in SD prevalence. Women living in urban area or eastern region seemed to be at higher risk of giving birth to children with SD, although they generally had a better socio-economic status and perinatal health care [12, 31]. However, urban area, and eastern region in China are more polluted than the rural area, central and western regions [32]. These findings indicate a role of maternal environmental exposures in the causal pathway of offspring syndactyly. It is very important to carry out etiological studies and interventions targeting syndactyly in these areas.
Previous studies have noted a link between maternal age and syndactyly. Pregnant women over 40 years of age were found to be more likely to have infants with syndactyly compared to younger women [33]. This study identified a higher SD prevalence in the maternal age group of 30–34 years and the highest prevalence of associated SD in the advanced maternal age (AMA) group. One explanation is that AMA can increase the risk of chromosomal anomalies and accompanying syndactyly [34]. However, multivariate Poisson regression models showed that the association between maternal age and syndactyly became insignificant after adjusting for year and other factors, suggesting temporal variations in maternal age-specific prevalence of syndactyly. Another explanation could be the older paternal age, that is generally associated with AMA, can increase gene mutations in sperm, thus increase the risk of some offspring skeletal malformations like Apert syndrome caused by FGFR2 mutations [35]. Most SD cases could be caused by de novo genetic variants as only a small percentage of cases had a family history. These findings indicate that parental age could affect SD prevalence [36, 37], and further investigations are warranted to elucidate the causes and mechanisms.
Anzeige
Our study also found that infants affected by syndactyly had poor pregnancy outcomes, particularly those affected by associated SD. Significantly higher preterm birth rate and low birth weight rate were observed for affected infants as compared with the general birth population [38, 39]. More than 20% of infants with associated SD were born prematurely or weighing < 2500 g. These figures were considerable higher than those reported in high-income countries [40]. The high perinatal mortality of our study may be partly due to those termination of pregnancies included in our analysis, but grouped as stillbirths. Nevertheless, the higher rate of early neonate death (4.4% for associated SD, 0.4% for isolated SD) compared with general Chinese newborns [13], suggests an urgent improvement in perinatal care and efficient interventions.
Syndactyly is phenotypically complex. In consistent with most published reports, right side preference and upper limb preference were confirmed in both isolated and associated syndactyly [4, 41, 42]. However, upper limbs and lower limbs were equally involved in several studies [30]. Both hands and feet involvements were rare in the current study (4.9%), lower than the percentage of 8% reported in a study [30]. Comparable to other studies, more than three-quarters of SDs occurred on one side of limbs, and the bilateral limb involvements were less than 20% [20, 42, 43]. Notably, more associated SD involved bilateral limbs and feet than isolated cases. The phenotypic heterogeneities between different SD malformations suggest the need for further genotype–phenotype studies.
Syndactyly can be accompanied by a variety of congenital abnormalities. Consistent with previous studies, anomalies of the musculoskeletal and circulatory systems were frequently associated with syndactyly [19]. Polydactyly was the most common malformation co-occurring with SD cases, indicating that polydactyly and SD may share some common genetic bases [23, 44]. Other major malformations such as oral clefts, eye, ear, and craniofacial abnormalities were also commonly associated with SD cases. Only 2.0% of associated cases were accompanied by chromosomal disorders, which could be underestimated because most pregnant women refused further examination once SD was confirmed due to its treatability. It is clear that SD cases with major malformations usually have a higher risk of adverse perinatal outcomes. The spectrum of congenital disorders co-occurring with SD needs to be further investigated as it may serve as an important predictor of prognosis.
Strengths and limitations
The main advantage of this study is the large sample-size, high-quality CBDMN data with wide geographical coverage and consistent case ascertainments, providing reliable estimates of SD prevalence in China. In addition, long-term surveillance data allows for an accurate characterization of syndactyly's secular trends and epidemiological features. One limitation is that hospital-based sample may introduce referral bias, although the effect is likely minimal given the high hospital delivery rate and neonate birth population in CBDMN member hospitals [45]. Other limitations include the short surveillance period and the inability to classify isolated syndactyly into subtypes due to coding system limitations. Overall, this study includes the largest sample of SD cases and accurately profiles syndactyly's epidemiological and clinical features in Chinese population over the past two decades.
Anzeige
Conclusions
In conclusion, the prevalence of syndactyly in China appears to be higher than that reported in other Asian countries and most European countries. The prevalence of syndactyly varies by maternal residence, maternal age, geographic region, and infant sex. The rising trend in prevalence, coupled with the poor perinatal outcomes among affected infants and the phenotypic variability, highlights the necessity of further etiological, epidemiological, and clinical studies on syndactyly in the contemporary Chinese population.
Acknowledgements
The authors thank the obstetricians, pediatricians, pathologists, and other participants involved in the CBDMN. The content of this article is solely the responsibility of the authors and do not represent the official view of the National Center for Birth Defects Monitoring.
Disclosure statement
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.
Declarations
Ethics approval and consent to participate
The current study analysed de-identified secondary data from the CBDMN. The CBDMN program was approved by the Ethics Committee of West China Second University Hospital, Sichuan University. Also, the Ethics Committee of West China Second University Hospital, Sichuan University waived the need for informed consent since the study was based on anonymised routine project monitoring data with no identifiable information on mothers. All procedures were performed in accordance with relevant guidelines.
Anzeige
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Trastuzumab deruxtecan scheint auch jenseits von Lungenkrebs gut gegen solide Tumoren mit HER2-Mutationen zu wirken. Dafür sprechen die Daten einer offenen Pan-Tumor-Studie.
Frauen mit lokalem oder metastasiertem Brustkrebs, die Statine einnehmen, haben eine niedrigere krebsspezifische Mortalität als Patientinnen, die dies nicht tun, legen neue Daten aus den USA nahe.
Welche Antibiotika darf man bei unkomplizierter Zystitis verwenden und wovon sollte man die Finger lassen? Welche pflanzlichen Präparate können helfen? Was taugt der zugelassene Impfstoff? Antworten vom Koordinator der frisch überarbeiteten S3-Leitlinie, Prof. Florian Wagenlehner.
Das Risiko, nach einem Gestationsdiabetes einen Typ-2-Diabetes zu entwickeln, hängt nicht nur von der Zahl, sondern auch von der Reihenfolge der betroffenen Schwangerschaften ab.
Update Gynäkologie
Bestellen Sie unseren Fach-Newsletter und bleiben Sie gut informiert – ganz bequem per eMail.