Introduction
Developmental delay is a term used for children who lack developmental features and skills in the language, motor and social developmental areas that would be expected of children of their age.
Objectives: The main objective was to determine the etiologic factors of developmental delay in children aged 5 months to 72 months at the child neurology unit of the Yaounde Gynaeco-Obstetric and Paediatric Hospital (YGOPH). Specifically, we were to determine the incidence of developmental delay in children less than 6 years, the socio-demographic profile, the main clinical presentations and causes of developmental delay in the child neurology unit.

Methodology
This was a cross-sectional descriptive study from 1st August 2012 to 1st January 2013 at the YGOPH. Were included in the study children aged 5months to 72 months, consulting at the child neurology unit of the YGOPH and having a developmental quotient less than 85. We excluded children whose parents refused to participate in the study. Detailed informations on the past history and development of the child were collected by interviewing their parents. The physical examination was done in the presence of a child neurologist. Further investigation was guided by the etiologic diagnosis. These informations were collected and recorded on a worksheet prepared for this purpose. Data was analysed using the software EPI INFO version 3.5.4. The chi-square test was used to compare variables. For all hypotheses tested, the level of significance of P value was <0.05.

Results
During the period of study, 2171 children age 5 months to 72 months consulted the paediatric department of YGOPH. Two hundred and ninety six of them were examined at the child neurology unit of the YGOPH and 178 had a developmental quotient less than 85. This gives a hospital prevalence of 8.2 % at the YGOPH and a prevalence of 60.1% at the child neurology unit for developmental delay. The mean age was 27.1 ± 18.2 months and the sex ratio was 1.28.
The main reason for consulting was tonus disorder (23.1%) and the developmental area of parental concern was the motor domain (87.1%). Regarding the clinical presentation, 67.4% of our population had cerebral palsy. Spastic quadriplegia was the main clinical picture of children with cerebral palsy (75.0%).
A severe delay was found in 14.2% of children, mild delay in 13.5%, moderate delay in 12.2%, profound delay in 11.1% of children and borderline children represented 9.1%. Normal children represented 39.9%. Gross developmental delay represented 87.1%.
Perinatal aetiologies were the main causes of developmental delay. Hypoxic ischemic encephalopathy (38.8%), epilepsy (13.5%), sequelae of meningitis (6.7%), sequelae of kernicterus (5.6%), and infectious embryofoetopathies (4.5%) were the most encountered aetiologies.
Drinking alcohol during pregnancy, young age of the mother, perinatal asphyxia and neonatal seizures were statistically significant factors that could cause a moderate, severe or profound developmental delay. The first child of the family was more likely to have a hypoxic ischemic encephalopathy at birth than others.

Conclusions
The prevalence of developmental delay at the child neurology unit and the YGOPH were 60.1% and 8.2% respectively. The average age of our patients was 27.1 (± 18.2) months and the sex ratio was 1.28. Most children had cerebral palsy and the main reason for consultation was tonus disorder. The main causes of mental neurodevelopmental delay are mainly perinatal (hypoxic ischemic encephalopathy, epilepsy, sequelae of meningitis, sequelae of kernicterus, and infectious embryofoetopathies).