Population red blood cell folate concentrations for prevention of neural tube defects: bayesian model

Abstract

Objective 

To determine an optimal population red blood cell (RBC) folate concentration for the prevention of neural tube birth defects.

Setting 

Data from two population based studies in China.

Participants 

247 831 participants in a prospective community intervention project in China (1993-95) to prevent neural tube defects with 400 μg/day folic acid supplementation and 1194 participants in a population based randomized trial (2003-05) to evaluate the effect of folic acid supplementation on blood folate concentration among Chinese women of reproductive age.

Intervention 

Folic acid supplementation (400 μg/day).

Main outcome measures 

Estimated RBC folate concentration at time of neural tube closure (day 28 of gestation) and risk of neural tube defects.

Results 

Risk of neural tube defects was high at the lowest estimated RBC folate concentrations (for example, 25.4 (95% uncertainty interval 20.8 to 31.2) neural tube defects per 10 000 births at 500 nmol/L) and decreased as estimated RBC folate concentration increased. Risk of neural tube defects was substantially attenuated at estimated RBC folate concentrations above about 1000 nmol/L (for example, 6 neural tube defects per 10 000 births at 1180 (1050 to 1340) nmol/L). The modeled dose-response relation was consistent with the existing literature. In addition, neural tube defect risk estimates developed using the proposed model and population level RBC information were consistent with the prevalence of neural tube defects in the US population before and after food fortification with folic acid.

Conclusions 

A threshold for “optimal” population RBC folate concentration for the prevention of neural tube defects could be defined (for example, approximately 1000 nmol/L). Population based RBC folate concentrations, as a biomarker for risk of neural tube defects, can be used to facilitate evaluation of prevention programs as well as to identify subpopulations at elevated risk for a neural tube defect affected pregnancy due to folate insufficiency.

Extracts:

How much natural food folate and/or folic acid intake is necessary to achieve red blood cell folate concentrations in the 1000-1300 nmol/L range in any given person or population is unknown. In the Folic Acid Dosing Trial in northern China, people consuming 100 μg/day in addition to usual diet (which is relatively low in other sources of folate) did not achieve a red blood cell folate concentration of 1000 nmol/L by the end of the six month supplementation trial. Those with the CC and CT genotypes who consumed 400 μg/day reached a red blood cell folate concentration of 1000 nmol/L between three and six months of supplementation, whereas those with the TT genotype
did not achieve a geometric mean red blood cell folate concentration of 1000 nmol/L by the six month sample.

Source:

Krista S Crider, et al, Population red blood cell folate concentrations for prevention of neural tube defects: bayesian model, BMJ 2014;349:g4554 

Free Fulltext:

http://www.bmj.com/content/349/bmj.g4554

Perinatal Hospice

Abstract:
When the prenatal diagnosis of a lethal fetal anomaly has been established, some patients choose to continue their pregnancy. Currently, there is a paucity of medical literature addressing the specific management of families in this unique circumstance. We propose a model of care that incorporates the strengths of prenatal diagnosis, perinatal grief management, and hospice care to address the needs of these families. We discuss the identification of candidates for this form of care; the multidisciplinary team approach; and the aspects of antepartum, intrapartum, and postpartum care. Finally, we discuss some barriers that might need to be overcome when attempting to implement perinatal hospice care.

Source:
Nathan J. Hoeldtke, Byron C. Calhoun, Perinatal Hospice, Am J Obstet Gynecol 2001;185:525-9
DOI: http://dx.doi.org/10.1067/mob.2001.116093

Free Fulltext:
http://www.aaplog.org/wp-content/uploads/2010/05/HoeldtkeCalhoun.pdf 

Birth Outcomes and Maternal Residential Proximity to Natural Gas Development in Rural Colorado

Abstract 

Background:

Birth defects are a leading cause of neonatal mortality. Natural gas development (NGD) emits several potential teratogens and US production is expanding.

 

Objectives: 

We examined associations between maternal residential proximity to NGD and birth outcomes in a retrospective cohort study of 124,842 births between 1996 and 2009 in rural Colorado.

 

Methods:

We calculated inverse distance weighted natural gas well counts within a 10-mile radius of maternal residence to estimate maternal exposure to NGD. Logistic regression, adjusted for maternal and infant covariates, was used to estimate associations with exposure tertiles for congenital heart defects (CHDs), neural tube defects (NTDs), oral clefts, preterm birth, and term low birth weight. The Association with term birth weight was investigated using multiple linear regression. 

 

Results:

Prevalence of CHDs increased with exposure tertile, with an odds ratio (OR) of 1.3 for the highest tertile (95% CI: 1.2, 1.5) and NTD prevalence was associated with the highest tertile of exposure (OR = 2.0, 95% CI: 1.0, 3.9, based on 59 cases), compared to no gas wells within a10-mile radius. Exposure was negatively associated with preterm birth and positively associated with fetal growth, though the magnitude of association was small. No association was foundbetween exposure and oral clefts. 

 

Conclusions:

In this large cohort, we observed an association between density and proximity of natural gas wells within a 10-mile radius of maternal residence and prevalence of CHDs and possibly NTDs. Greater specificity in exposure estimates are needed to further explore these associations. 

 

Journal Reference:

Lisa M. McKenzie et al,  Birth Outcomes and Maternal Residential Proximity to Natural Gas Development in Rural Colorado, Environ Health Perspect; DOI:10.1289/ehp.1306722

 

Free Fulltext:

http://ehp.niehs.nih.gov/wp-content/uploads/122/1/ehp.1306722.pdf

Monoamniotic Twins with One Fetal Anencephaly and Cord Entanglement Diagnosed with Three Dimensional Ultrasound at 14 Weeks of Gestation

Abstract:
A 29-year-old pregnant woman with parity 0-0-0-0 was diagnosed with monoamniotic twin pregnancy discordant for anencephaly at 14 weeks gestation. Umbilical cord entanglement, which is an important cause of fetal death in monoamniotic twins, was confirmed by three-dimensional ultrasound. Cesarean section was performed at 34 weeks of gestation, and the normal newborn infant was discharged without any complications. We report a case of monoamniotic twin pregnancy discordant for anencephaly and diagnosed with cord entanglement by three-dimensional ultrasound at 14 weeks of gestation, and now report it along with a literature review.

Journal Reference:
Jo YS, Son HJ, Jang DG, Kim N, Lee G. Monoamniotic Twins with One Fetal Anencephaly and Cord Entanglement Diagnosed with Three Dimensional Ultrasound at 14 Weeks of Gestation. Int J Med Sci 2011; 8(7):573-576. doi:10.7150/ijms.8.573.

Free Fulltext:
http://www.medsci.org/v08p0573.htm