In a wide variety of species, a female's age of first reproduction influences offspring size and survival, suggesting that there exists an optimal timing of reproduction. Mothers in many species also influence offspring size and survival after birth through variation in parental care. We experimentally separated these effects in the burying beetle Nicrophorus vespilloides to test for coadaptati...

Significant alteration in timing of tooth eruption with the first teeth being present at birth or erupting during month life is a rare occurrence humans. Timing may be affected by hereditary, endocrine and environmental factors. The presence natal lead to complications such as discomfort suckling, laceration mother’s breasts, sublingual ulceration resultant feed refusal, aspiration making extra...

We analyze the impact of birth seasonality (seasonal oscillations in the birth rate) on the dynamics of acute, immunizing childhood infectious diseases. Previous research has explored the effect of human birth seasonality on infectious disease dynamics using parameters appropriate for the developed world. We build on this work by including in our analysis an extended range of baseline birth rat...

BACKGROUND The age at which childbearing begins influences the total number of children a woman bears throughout her reproductive period, in the absence of any active fertility control. For countries in sub-Saharan Africa where contraceptive prevalence rate is still low, younger ages at first birth tend to increase the number of children a woman will have thereby hindering the process of fertil...

OBJECTIVES To test the contraceptive confidence hypothesis in a modern context. The hypothesis is that women using effective or modern contraceptive methods have increased contraceptive confidence and hence a shorter interval between marriage and first birth than users of ineffective or traditional methods. We extend the hypothesis to incorporate the role of abortion, arguing that it acts as a ...

Ages at menarche and first birth are established risk factors for breast cancer. The interval between these ages may also affect risk, since the breast is more susceptible to carcinogenic insults during this period than during the parous period. However, few investigators have studied this relation. Using logistic regression, the authors evaluated associations between the timing of reproductive...

1 Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA. 2 Department of Preventive Medicine, Keck School of Medicine and Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA. 3 Division of Reproductive Health, Centers for Disease Control and Prevention, Atlanta, GA. 4 Center for Clinical Epidemiology and Biostatistics and Depa...

BACKGROUND In 1999, the American Academy of Pediatrics and U.S. Public Health Service recommended suspending the birth dose of hepatitis B vaccine due to concerns about potential mercury exposure. A previous report found that overall national hepatitis B vaccination coverage rates decreased in association with the suspension. It is unknown whether this underimmunization occurred uniformly or wa...