Several studies have shown that abnormal head sizes are among the most common genetic disorders and birth defects worldwide.[8
] The current study is one of the earliest emerging reports worldwide exploring the socio-demographic and pregnancy-related antecedents of infants with abnormal head sizes, based on the latest WHO-CGS, but with specific reference to a country with low income. The principal findings from this community-based study are that maternal age, educational level, pregnancy type, and place of delivery are significantly associated with abnormal head size in early infancy. Even when adjusted for place of delivery, the socio-demographic factors still remain significant. These findings are in contrast with a related hospital-based study in which a comparable incidence of abnormal head sizes (12.9%) was observed, but no association was established between the maternal socio-demographic profile and abnormal sizes at birth.[15
] Taken together, the current study would suggest that the socio-demographic factors were more predictive of acquired or progressive rather than congenital abnormal head sizes. Barring the lack of evidence from a more robust longitudinal study from birth, the current findings are quite plausible, considering the potential role of asymptomatic and ubiquitous infections like the Cytomegalovirus
, which is characteristically progressive.[16
] Perhaps, more notably is an indication that adverse environmental or early postnatal conditions are likely to play a more dominant role than genetic factors in the etiology of abnormal head sizes in countries with low income, such as Nigeria.
Perhaps the most striking observation from this study is that infants delivered outside government-run public hospitals, especially in private hospitals or in homes, were at 50% increased risk of having abnormal head sizes. The exact mechanism underlying this association is unclear and merits further investigation, considering the high proportion of such deliveries in many resource-poor countries. For example, public hospitals are usually better equipped and better staffed with various levels of obstetric professionals than what most private hospitals in low-income countries can afford. Thus, the quality of puerperal and perinatal care, especially resuscitation practices available outside public hospitals is often lower, exacerbated by the lack of, or poorly enforced regulatory standards. The lesser risk of abnormal head size among infants delivered in traditional maternity homes may not be unconnected, with the practice of the traditional birth attendants to refer high-risk pregnancies, including first-time parturients, in this population to public hospitals.
The association with teenage mothers contrasts with findings from developed countries where older mothers (≥35 years old) have been associated with microcephalic offspring.[18
] It is plausible that the finding among teenagers in the current study may be attributable to the competing nutritional needs of pregnancy underpinned by the mother's biological immaturity and growth. This situation is likely to be exacerbated in nutritionally deprived adolescent girls in poor communities, with poor micronutrient intake, resulting in reduced placental growth and fetal size.[19
] The high risk of abnormal head size among mothers with no or low education is in agreement with other studies,[18
] while the highest risk reported among infants in multiple gestation is not unexpected, based on the extensive evidence in literature on the associated congenital malformations.[8
Overall, this study suggests that the maternal socio-demographic profile, including the place of delivery, is crucially relevant toward any efforts to curtail the burden of abnormal head sizes and the demand for scarce community-based rehabilitation services in low-income countries. The high uptake of antenatal visits offers an opportunity to educate mothers on the avoidable risk factors for abnormal head sizes. In particular, poor interpersonal encounters with maternity staff and long waiting times in public hospitals are not uncommon, and have been noted as major incentives for delivery in private hospitals or at home. These issues also need to be addressed. Although it was impracticable to examine the perinatal or early postnatal outcomes associated with abnormal head sizes in this community-based setting, this study complements the hospital-based study, which identified intrauterine growth restriction, under-nutrition, hyperbilirubinemia, and neonatal sepsis as probable outcomes.[15
A few limitations of this retrospective and essentially exploratory study are worth noting. For example, the study sample was restricted to survivors during the enrolment period, which would have made it impossible to ascertain the true incidence of abnormal head sizes. The study also excluded preterm infants, as they would have required modification to the WHO-CGS standards designed for term infants. Case finding was based solely on WHO-CGS standards and no attempt was made to compare the results with other growth standards. As a cross-sectional study, it was difficult to accurately discriminate between congenital, acquired, progressive, or even arrested abnormal head sizes. Additionally, the community-based design of this study precluded reliable data on important variables such as mode of delivery, maternal nutritional status, and non-pregnancy related factors such as exposure to drugs, infections, and radiation. Nonetheless, the study provides initial evidence on the application of the WHO-CGS for early detection and intervention for infants at risk of diverse neurodevelopmental disorders, underpinned by abnormal head sizes, in developing countries.