Background

Congenital hydrocephalus (CH) is a group of neurological disorders caused by various reasons that all result in imbalance between the production and absorption of cerebrospinal fluid (CSF) [1]. The main characteristics are the accumulation of CSF in the cranial cavity and ventricular dilatation [2]. Besides a strong genetic background, prematurity, infection, and intracranial structural malformations such as neural tube defects (NTDs) and aqueduct stenosis can give rise to CH [3,4,5,6]. CH resulting from brain anomalies always have poor prognosis, particularly high neonatal fatality rate and impaired mental development. Although surgical interventions are widely used to improve the health of the affected children, life-long treatment or multidisciplinary care are needed. The prevalence of CH varied between 4 and 12 per 10,000 births [7,8,9,10,11,12,13]. The reported prevalence of CH in provinces of China ranged from 6.9 to 9.2 per 10,000 births [11,12,13]. Based on data from the Chinese Birth Defects Monitoring Network (CBDMN), an overall prevalence rate of 7.03/10,000 and an upward trend were observed during 1996–2004 [14]. Health care services for women and children have been improved considerably in China over the recent decade [15]. In particular, lots of medical institutions have been established to provide prenatal screening and diagnosis services for pregnant women since the National Regulation on the Administration of Prenatal Diagnosis Techniques took effect in 2003 [16], which led to the improvement of prenatal diagnosis and an increase in termination of pregnancies with severe birth defects. These changes had a great impact on the birth prevalence of certain birth defects in China, such as NTDs and Down syndrome [17, 18]. However, whether CH prevalence was affected by changes of the policy remains unknown. This study aimed to investigate recent changes in the prevalence of CH and perinatal outcomes of the affected neonates based on newly updated CBDMN database.

Methods

Study subjects

Data on CH cases and newborns in the study were abstracted from CBDMN, a nationwide hospital-based birth defects surveillance program in China, with monitoring period from 28 weeks of gestation to 7 days after birth. The procedure of data collection, case ascertainment and data quality management has been described in detail elsewhere [19, 20]. In brief, a three-level (county, province, and central) surveillance network and corresponding expert groups were established to perform routine data collection. Summary data of all births (live or stillbirths ≥ 28 weeks of gestation) and information of individual birth defect cases were collected with standardized forms by hospital staff and then checked by expert groups at each level. In addition, an independent retrospective survey was organized to identify underreporting of birth defects and inaccuracies in data, and database was subsequently updated prior to annual reporting. CBDMN adopts the same criteria of CH cases as described by the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR) [21]. CH cases characterized by dilatation of the cerebral ventricles and diagnosed prenatally or within the first week of life were included, and cases caused by premature birth, intraventricular haemorrhage or secondary to NTDs were excluded. We searched the CBDMN database from January 2005 to December 2012 for all births with a diagnosis of hydrocephalus, with any of the following ICD-10 codes were included in the study: Malformations of the aqueduct of Sylvius (Q03.0); Atresia of foramina of Magendie and Luschka, also called Dandy-Walker syndrome (Q03.1); other specified types of congenital hydrocephalus (Q03.8); and unspecified congenital hydrocephalus (Q03.9). Based on whether accompanied by additional malformations in other systems or organs, CH cases were divided into two subgroups: isolated CH and associated CH [7, 9].

Maternal age (<20, 20–24, 25–29, 30–34, ≥35 years), residential area (urban, rural), gender, and plurality of pregnancy were obtained for all births and CH cases. Residential areas were classified into urban (cities and towns) and rural (villages and countryside) areas based on mother’s last residence address where she lived for at least 1 year [20]. Birth weight (<2500, 2500–3999, ≥4000 g), gestational age (28–36, 37–41, ≥42 weeks), perinatal outcomes (stillbirth, early neonate death and alive within 7 days), and time of diagnosis were acquired for CH cases.

Statistical analysis

The prevalence of CH was calculated as the number of CH cases, divided by the total number of live birth and stillbirth in CBDMN database during the 8-year period of the study. The changes in prevalence over the study period were analyzed by linear chi-square test [22]. CH prevalence stratified by maternal age, residential area, gender and plurality of pregnancy were compared by calculating prevalence ratios (PR) and 95% confidence intervals (95% CI) with Poisson regression model. All statistical analyses were performed with SPSS 21. The statistical significance level for α was set at 0.05.

Results

During the study period, a total of 6490 CH cases (5245 isolated and 1245 associated cases) were identified among 10,574,061 births, yielding a prevalence of 6.14, 4.96, and 1.18 per 10,000 births for the overall, isolated, and associated CH, respectively. There was a downward trend in the annual prevalence of overall CH (from 7.52 to 5.98 per 10,000 births, P < 0.001) and isolated CH (from 6.17 to 4.19 per 10,000 births, P < 0.001), but not in the prevalence of associated CH (Fig. 1).

Fig. 1
figure 1

Trends in Prevalence of Congenital Hydrocephalus in China, 2005–2012

Full size image

The prevalence of isolated and associated CH varied significantly between groups stratified by maternal age, residential area, gender and plurality of pregnancy (Table 1). Both younger and older maternal age were associated with higher CH prevalence as compared to the maternal age group of 20–24 years. The highest prevalence of isolated CH was observed in maternal age < 20 years group (PR: 1.88, 95% CI: 1.60–2.22), whereas the highest prevalence of associated CH was in ≥35 years maternal age group (PR: 1.98, 95% CI: 1.67–2.36). Higher prevalence was also found in infants born to mothers who resided in rural areas (PR: 1.40, 95% CI: 1.34–1.48), infants with male sex (PR: 1.12, 95% CI: 1.06–1.17), and multiple births (PR: 2.55, 95% CI: 2.25–2.90).

Table 1 Prevalence of congenital hydrocephalus (1/10,000) in China during 2005–2012, stratified by maternal age, residential area, gender, and plurality of pregnancy
Full size table

Among 6490 CH cases, 5737 (88.47%) cases were diagnosed prenatally, 4942 (76.15%) cases were terminations of pregnancy (TOP). Characteristics of 1548 non-aborted CH cases were shown in Table 2, the low birth weight rate of associated CH was higher than that of isolated CH (45.98% vs 35.82%). Of infants affected by CH, 37.53% were born prematurely. The total stillbirth rate of CH was 34.35%. The early neonatal mortality rates (ENMR) were 17.93% (135/753), 28.63% (75/262) and 20.69% (210/1015) for the isolated, associated and overall hydrocephalus, respectively. ENMR of CH in rural area (141/578, 24.39%) was significantly higher than that in urban area (69/437, 15.79%).

Table 2 Characteristics of 1548 non-aborted cases with congenital hydrocephalus
Full size table

Discussion

By analyzing almost 10 million birth data in CBDMN, we identified an overall prevalence of 6.14/10,000 for CH during 2005 to 2012, which was significantly lower than the rate of 7.03/10,000 during 1996–2004 (P < 0.001) [14]. The overall rate in our study also appeared lower than those from previous studies conducted in mainland China (6.9–9.2/10,000) [

Conclusions

In conclusion, our analyses found a downward trend in birth prevalence of CH in China since 2005, and the prevalence varied significantly by maternal age, gender, residential area and plurality of pregnancy. The findings of relatively high prevalence and poor perinatal outcomes of infants with hydrocephalus are of great value for future study.