ABSTRACT
Newborns were monitored for congenital malformations in four government hospitals located in high-level (ambient dose >1.5 mGy/year) and normal-level (≤ 1.5 mGy/year) natural radiation areas of Kerala, India, from August 1995 to December 2012. Sex ratio at birth (SRB) among live singleton newborns and among previous children, if any, of their mothers without history of any abortion, stillbirth or twins is reported here. In the absence of environmental stress or selective abortion of females, global average of SRB is about 1050 males to 1000 females. A total of 151,478 singleton, 1031 twins, 12 triplets and 1 quadruplet deliveries were monitored during the study period. Sex ratio among live singleton newborns was 1046 males (95 % CI 1036-1057) for 1000 females (77,153 males:73,730 females) and was comparable to the global average. It was similar in high-level and normal-level radiation areas of Kerala with SRB of 1050 and 1041, respectively. It was consistently more than 1000 and had no association with background radiation levels, maternal and paternal age at birth, parental age difference, gravida status, ethnicity, consanguinity or year of birth. Analysis of SRB of the children of 139,556 women whose reproductive histories were available suggested that couples having male child were likely to opt for more children and this, together with enhanced rate of males at all birth order, was skewing the overall SRB in favour of male children. Though preference for male child was apparent, extreme steps of sex-selective abortion or infanticide were not prevalent.
Subject(s)
Abnormalities, Radiation-Induced/epidemiology , Background Radiation , Prenatal Exposure Delayed Effects/epidemiology , Radiation Dosage , Radiation Exposure/statistics & numerical data , Sex Ratio , Dose-Response Relationship, Radiation , Female , Humans , India/epidemiology , Infant, Newborn , Male , Pregnancy , Prevalence , Radiation Exposure/analysis , Radiation Monitoring/statistics & numerical data , Risk AssessmentABSTRACT
Monitoring newborns for adverse outcomes like stillbirth and major congenital anomalies (MCA) is being carried out in government hospitals since 1995 in and around high-level natural radiation areas, a narrow strip of land on the southwest coast of Kerala, India. Natural deposits of monazite sand containing thorium and its daughter products account for elevated levels of natural radiation. Among 141,540 newborns [140,558 deliveries: 139,589 singleton, 957 twins (6.81 ), 11 triplets (0.078 ), and one quadruplet] screened, 615 (4.35 ) were stillbirth and MCA were seen in 1,370 (9.68 ) newborns. Clubfoot (404, 2.85 ) was the most frequent MCA followed by hypospadias (152, 2.10 among male newborns), congenital heart disease (168, 1.19 ), cleft lip/palate (149, 1.05 ), Down syndrome (104, 0.73 ), and neural tube defects (72, 0.51 ). Newborns with MCA among stillbirths were about 20-fold higher at 190.24 (117/615) compared to 8.89 (1,253/140,925) among live births (P < .001). Logistic regression was carried out to compare stillbirth, overall, and specific MCA among newborns from areas with dose levels of ≤1.5, 1.51-3.0, 3.01-6.0 and >6 mGy/year after controlling for maternal age at birth, gravida, consanguinity, ethnicity, and gender of the baby. Clubfoot showed higher prevalence of 3.26 at dose level of 1.51-3.0 mGy/year compared to 2.33 at ≤1.5 mGy/year (OR = 1.39; 95 % CI, 1.12-1.72), without indication of any clear dose-response. Prevalences of stillbirth, overall MCA, and other specific MCA were similar across different dose levels and were relatively lower than that reported elsewhere in India, probably due to better literacy, health awareness, and practices in the study population.
