Epidemiology of birth defects in teenage pregnancies: Based on provincial surveillance system in eastern China

Abstract Background Globally, access to healthcare and diagnostic technologies are known to substantially impact the reported birth prevalence of congenital heart disease (CHD). Previous studies have shown marked heterogeneity between different regions, with a suggestion that CHD prevalence is rising globally, but the degree to which this reflects differences due to environmental or genetic risk factors, as opposed to improved detection, is uncertain. We performed an updated systematic review to address these issues. Methods Studies reporting the birth prevalence of CHD between the years 1970–2017 were identified from searches of PubMed, EMBASE, Web of Science and Google Scholar. Data on the prevalence of total CHD and 27 anatomical subtypes of CHD were collected. Data were combined using random-effect models. Subgroup and meta-regression analyses were conducted, focused on geographical regions and levels of national income. Results Two hundred and sixty studies met the inclusion criteria, encompassing 130 758 851 live births. The birth prevalence of CHD from 1970–2017 progressively increased to a maximum in the period 2010–17 of 9.410/1000 [95% CI (confidence interval) 8.602–10.253]. This represented a significant increase over the fifteen prior years (P = 0.031). The change in prevalence of mild CHD lesions (ventricular septal defect, atrial septal defect and patent ductus arteriosus) together explained 93.4% of the increased overall prevalence, consistent with a major role of improved postnatal detection of less severe lesions. In contrast the prevalence of lesions grouped together as left ventricular outflow tract obstruction (which includes hypoplastic left heart syndrome) decreased from 0.689/1000 (95% CI 0.607–0.776) in 1995–99, to 0.475/1000 (95% CI 0.392–0.565; P = 0.004) in 2010–17, which would be consistent with improved prenatal detection and consequent termination of pregnancy when these very severe lesions are discovered. There was marked heterogeneity among geographical regions, with Africa reporting the lowest prevalence [2.315/1000 (95% CI 0.429–5.696)] and Asia the highest [9.342/1000 (95% CI 8.072–10.704)]. Conclusions The reported prevalence of CHD globally continues to increase, with evidence of severe unmet diagnostic need in Africa. The recent prevalence of CHD in Asia for the first time appears higher than in Europe and America, where disease ascertainment is likely to be near-complete, suggesting higher genetic or environmental susceptibility to CHD among Asian people.

Purpose To examine pregnancy rates and outcomes (births and abortions) among 15- to 19-year olds and 10- to 14-year olds in all countries for which recent information could be obtained and to examine trends since the mid-1990s. Methods Information was obtained from countries’ vital statistics reports and the United Nations Statistics Division for most countries in this study. Alternate sources of information were used if needed and available. We present estimates primarily for 2011 and compare them to estimates published for the mid-1990s. Results Among the 21 countries with complete statistics, the pregnancy rate among 15- to 19-year olds was the highest in the United States (57 pregnancies per 1,000 females) and the lowest rate was in Switzerland (8). Rates were higher in some former Soviet countries with incomplete statistics; they were the highest in Mexico and Sub-Saharan African countries with available information. Among countries with reliable evidence, the highest rate among 10- to 14-year olds was in Hungary. The proportion of teen pregnancies that ended in abortion ranged from 17% in Slovakia to 69% in Sweden. The proportion of pregnancies that ended in live births tended to be higher in countries with high teen pregnancy rates (p =.02). The pregnancy rate has declined since the mid-1990s in the majority of the 16 countries where trends could be assessed. Conclusions Despite recent declines, teen pregnancy rates remain high in many countries. Research on the planning status of these pregnancies and on factors that determine how teens resolve their pregnancies could further inform programs and policies.

Previous studies have suggested that etiologic heterogeneity may complicate epidemiologic analyses designed to identify risk factors for birth defects. Case classification uses knowledge of embryologic and pathogenetic mechanisms to make case groups more homogeneous and is important to the success of birth defects studies. The goal of the National Birth Defects Prevention Study (NBDPS), an ongoing multi-site case-control study, is to identify environmental and genetic risk factors for birth defects. Information on environmental risk factors is collected through an hour-long maternal interview, and DNA is collected from the infant and both parents for evaluation of genetic risk factors. Clinical data on infants are reviewed by clinical geneticists to ensure they meet the detailed case definitions developed specifically for the study. To standardize the methods of case classification for the study, an algorithm has been developed to guide NBDPS clinical geneticists in this process. Methods for case classification into isolated, multiple, and syndrome categories are described. Defects considered minor for the purposes of case classification are defined. Differences in the approach to case classification for studies of specific defects and of specific exposures are noted. The case classification schema developed for the NBDPS may be of value to other clinicians working on epidemiologic studies of birth defects etiology. Consideration of these guidelines will lead to more comparable case groups, an important element of careful studies aimed at identifying risk factors for birth defects.