Fertility

About: Fertility is a research topic. Over the lifetime, 29988 publications have been published within this topic receiving 681106 citations.

Laboratory semen assessment and prediction of fertility: still utopia?

Abstract: Finding a laboratory test reliable enough to predict the potential fertility of a given semen sample or a given sire for artificial insemination (AI) is still considered utopian, as indicated by the modest correlations seen between results obtained in vitro and field fertility. Male fertility is complex, and depends upon a heterogeneous population of spermatozoa interacting at various levels of the female genital tract, the vestments of the oocyte, and the oocyte itself. For this reason, laboratory assessment of semen must include the testing of most sperm attributes relevant for fertilization and embryo development, not only in individual spermatozoa but within a large sperm population as well. Strategies for the discovery of in vitro predictors of semen fertility require evaluations of low sperm doses for AI, so that differences in innate in vivo fertility can be accurately detected.

Education, HIV, and Early Fertility: Experimental Evidence from Kenya

Abstract: A seven-year randomized evaluation suggests education subsidies reduce adolescent girls’ dropout, pregnancy, and marriage but not sexually transmitted infection (STI). The government’s HIV curriculum, which stresses abstinence until marriage, does not reduce pregnancy or STI. Both programs combined reduce STI more, but cut dropout and pregnancy less, than education subsidies alone. These results are inconsistent with a model of schooling and sexual behavior in which both pregnancy and STI are determined by one factor (unprotected sex), but consistent with a two-factor model in which choices between committed and casual relationships also affect these outcomes.

Is lowest-low fertility in Europe explained by the postponement of childbearing?

Abstract: In 2001, more than half of Europe's population lived in countries with a total fertility rate (TFR) at or below 1.3. Use of the adjusted TFR proposed by Bongaarts and Feeney, which takes into account the effects of the ongoing fertility postponement, changes the European fertility map considerably. All 27 countries analyzed had adjusted TFRs in 1995–2000 above 1.4. Thus, the “lowest-low” fertility in Europe may be interpreted as a temporary consequence of the increasing age at motherhood. However, substantial regional differences in fertility level across Europe persist even when the differential pace of fertility postponement is taken into account. The estimated adjusted TFRs in Europe (1.63) and in the 25-member European Union (1.71) contrast with the TFR levels of 1.40 and 1.46, respectively. These seemingly small differences have vastly different implications in terms of the potential long-term pace of population decline.

Rethinking the evolutionary theory of aging: Transfers, not births, shape senescence in social species

Abstract: The classic evolutionary theory of aging explains why mortality rises with age: as individuals grow older, less lifetime fertility remains, so continued survival contributes less to reproductive fitness. However, successful reproduction often involves intergenerational transfers as well as fertility. In the formal theory offered here, age-specific selective pressure on mortality depends on a weighted average of remaining fertility (the classic effect) and remaining intergenerational transfers to be made to others. For species at the optimal quantity–investment tradeoff for offspring, only the transfer effect shapes mortality, explaining postreproductive survival and why juvenile mortality declines with age. It also explains the evolution of lower fertility, longer life, and increased investments in offspring.