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Published on: March 14, 2013
Sex Differences in Nutrition, Growth, and Metabolism in Preterm Infants
1Division of Neonatology, Department of Pediatrics, University of Mississippi Medical Center, Jackson, MS, United States.
Insights
Male and female fetuses exhibit distinct biological responses to the intrauterine environment, with females showing a natural survival advantage. These sex-specific differences influence fetal growth, placental development, and susceptibility to adverse conditions.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Perinatal Medicine
Background:
- Biological sex differences manifest early in pregnancy, impacting fetal development and placental function.
- Maternal factors like glucocorticoids (GC) and pre-pregnancy health influence fetal growth and maturation in sex-specific ways.
- Existing research suggests females possess a natural survival advantage in utero.
Purpose of the Study:
- To explore the sex-specific biological variations in fetal development and response to the intrauterine environment.
- To investigate the role of maternal factors, such as glucocorticoids and pre-pregnancy obesity, in sex-specific fetal outcomes.
- To understand the molecular and cellular basis for differential responses between male and female fetuses.
Main Methods:
- Comparative analysis of fetal growth parameters (e.g., crown-rump length) between sexes.
- Examination of placental protein and gene expression differences.
- Review of existing literature on maternal health conditions (pre-eclampsia, asthma, gestational diabetes) and their sex-specific fetal impacts.
- Analysis of extracellular microRNA profiles in relation to fetal sex.
Main Results:
- Male fetuses are larger in crown-rump length during the first trimester.
- Placentae show sex-specific protein and gene expression, particularly under adverse conditions.
- Females exhibit upregulation of certain microRNAs, while males show downregulation.
- Maternal pre-pregnancy obesity and gestational diabetes are linked to increased childhood obesity risk in males but not females.
- Female fetuses demonstrate adaptive growth responses to maternal conditions like mild pre-eclampsia, while males may experience Intrauterine Growth Restriction (IUGR) or preterm delivery.
Conclusions:
- Male and female fetuses respond distinctly to the same intrauterine environment, indicating fundamental biological variations.
- Females appear to have a natural survival advantage due to adaptive responses to intrauterine stress.
- Sex-specific programming during gestation influences long-term health outcomes, including susceptibility to adult diseases.
- Further research into cellular and molecular mechanisms underlying these sex differences is warranted.
Abstract:
Biological differences between the sexes are apparent even from the early part of the pregnancy. The crown-rump length is larger in male fetuses compared to females in the first trimester. Placentae of male and female fetuses have different protein and gene expressions, especially in adverse conditions. Even within the intrauterine milieu, the same extracellular micro RNA may show upregulation in females and downregulation in male fetuses. There appears to be a natural survival advantage for females. Maternal glucocorticoids (GC) play an important role in fetal growth and organ maturation. However, excess glucocorticoids can not only affect growth but the response may be sex-specific and probably mediated through glucocorticoid receptors (GR) in the placenta. Mild pre-eclampsia and asthma are associated with normal growth pattern in males, but in female fetuses, they are associated with a slowing of growth rate without causing IUGR probably as an adaptive response for future adverse events. Thus, female fetuses survive while male fetuses exhibit IUGR, preterm delivery and even death in the face of another adverse event. It is thought that the maternal diet may not influence growth but may influence the programming for adult disease. There is growing evidence that maternal pre-pregnancy overweight or obesity status is directly associated with a higher risk of obesity in a male child, but not in a female child, at 1 year of age. It is observed that exposure to gestational diabetes is a risk factor for childhood overweight in boys but not in girls. It is fascinating that male and female fetuses respond differently to the same intrauterine environment, and this suggests a fundamental biological variation most likely at the cellular and molecular level.
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