The prevalence of birth defects in the present study is 0.58% which is comparable with the earlier studies in Iraq and Iran which reported an incidence of 0.69% and 0.36%[18-20]. The patterns of system involved in our study show Musculoskeletal System to be most commonly affected presenting as cleft lip, cleft palate and club feet. This was in line with the study conducted in different parts of world in Egypt and India [21, 22]. A study in Iran and India reported higher prevalence of malformations from CNS, Cardiovascular system or Gastrointestinal system[23, 24]. This variation in patterns could possibly be explained by various genetic and environmental factors interplaying differently in varied time and geographical location[10].
Mothers of age group less than 20 years were found to have risk of delivering a newborn with birth defect which was similar to the study which concluded association between young mothers and congenital anomaly[25]. In contrast, several studies have identified the potential of maternal age above 35 years in the causation of this condition [10, 26]. Developmental and behavioural factors like poor diet, illicit drug use, smoking etc in the adolescent group as compared to older mothers relative to conception could likely affect the developing foetus[25].
According to different literatures, congenital malformation is seen in twins rather than singleton pregnancy[10, 27]. Likewise, our finding enlisted this study as one among those many. However, multiple delivery did not pose a risk to birth defect in Europe [28]. Alterations of the blood flow within the vascular anastomoses supplying the twins and early primary abnormality that might develop during twinning itself can lead to birth defects[29].
In comparison to women with no previous birth, the likelihood of giving birth to a baby with congenital defect was seen among women with 1 or more previous birth in our study, which is similar to those reported in other studies[25, 30]. To the contrary, positive association between nulliparity and range of birth defects have also been successfully investigated earlier[31, 32]. The decrement in body nutrients stores among mothers who have previously delivered as compared to those who have never delivered a baby before explains the association between parity and congenital birth defects[33].
With regards to ethnicity, advantageous ethnic groups like Brahmin and Chettri were comparatively less likely to be associated with birth defects than the non-advantageous group. Association of ethnicity with birth defects has been depicted in the previously done studies[25, 34]. Ethnic variance as the risk for malformations may be linked to genetic susceptiveness or to socio-cultural and economic differences that might modify exposures[35].
This study showed that there was significant impact for female sex in regards to the causation of congenital birth anomalies and this significance is also supported by studies from neighbouring nations[36]. In contrast, male babies were found to have risk for birth defects in another study[36, 37]. This variation could probably be explained by potential of the hormonal hypothesis of sex ratio explaining the unusual concentrations of hormones during or preceding pregnancy could be more common in those malformations with established sex ratio biases[38].
Studies have documented that conditions like cleft lip and polydactyly are more common in males whereas neural tube defects and cleft palate are more seen among female babies [39, 40]. The high incidence of cleft palate and NTDs could also explain female preponderance to for birth defects. However, as we have not examined population-based resources in this study, this might not potentially explain the exact sex difference patterns in babies with congenital birth anomalies.
Babies with birth defects tend to have morbidities such as birth asphyxia and neonatal infection as found in this study. The risk of mortality among these babies at birth is higher similarly. Increased mortality arising from birth defects has also been identified in India[41]. This can be explained based on the type of defect or anomalies which describes the intensity or level of risk associated.
Limitations
There are some limitations in this study. A community-based study rather than a hospital-based study can better project prevalence and in our settings echocardiography and other advanced diagnostics were not routinely available to diagnose malformations[21]. Further, stillbirths were not included in the study which might also have attributed to the lower prevalence. Birth defects may have been underreported as diagnosis could not have been made at birth. Many birth defects such as congenital heart defects are likely not identified at birth.