This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Adolescent pregnancy is a significant public health problem in the United States. Each year, approximately 1 million teenagers in this country become pregnant. Of these adolescents, more than half a million teens bear children and over 175,000 of these new mothers are age 17 or younger. Special nutritional concerns are evident in this group to insure that calcium needs can be met by both the fetus and the adolescent who has not yet consolidated her skeletal mass.
The specific aims of the proposed study are to: 1) Determine the relationships between maternal Ca intake and vitamin D status on maternal bone mass and fetal bone growth across pregnancy, 2) Assess the impact of maternal Ca intake and vitamin D status on maternal total body Ca content and maternal/neonatal hormone concentrations at parturition and 3) To evaluate mechanisms of maternal / fetal Ca transfer at the level of the placenta by characterizing the localization and expression of proteins and receptors involved in placental Ca transport in relation to maternal calcium and vitamin D status. To accomplish these aims, longitudinal heel ultrasound measures and fetal sonogram measures will be obtained in a group of 300 adolescents (ages 11-18 y) at entry into prenatal care (week 12-16 of gestation), during week 21-25 of gestation and again at week 31-35 of gestation. Maternal hormonal status and biochemical measures of bone homeostasis will be measured in all adolescents at week 21-25 of pregnancy. At delivery, in a subset of 100 adolescents, maternal and cord blood will be collected for analysis of calcitropic hormones and biochemical measures of bone homeostasis and maternal total body bone mineral content and lumbar spine bone mineral density will be measured. Placental tissue will also be collected at delivery to address the regulation of proteins involved in Ca transport to the fetus in relation to neonatal Ca status and maternal Ca intake and vitamin D status across pregnancy. Data from the proposed studies will assist in recommendations for optimal nutrient intakes in this population and will provide novel information on the dynamics of Ca metabolism during the key life stage in a population at high risk for Ca and vitamin D insufficiency. The objectives of this study will directly address the purpose and priorities specified by Section 31.0 Improving Human Nutrition for Optimal Health by specifically focusing on nutrient requirements in pregnant adolescents an the molecular mechanisms utilized at the level of the placenta to insure sufficient nutrient transfer to the developing fetus.
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