Fertility Rate

Lowest-low fertility, defined as a period total fertility rate at or below 1.3, has rapidly spread in Europe during the 1990s. This article traces the emergence of this new phenomenon to the interaction of five factors. First, tempo and compositional distortions reduce the total fertility rate below the associated level of cohort fertility. Second, socioeconomic changes—including increased returns to human capital and high economic uncertainty in early adulthood—have made late childbearing a rational response for individuals and couples. Third, social interaction effects reinforce this behavioral adjustment and contribute to large and persistent postponement in the mean age at birth. Fourth, institutional settings favor an overall low quantum of fertility. Fifth, postponement–quantum interactions amplify the consequences of this institutional setting when combined with ongoing delays of child-bearing. The article concludes with speculations about future trends in current and prospective lowest-low-fertility countries.

Period fertility rates fell to previously unseen low levels in a large number of countries beginning in the early 1990s. The persistence of Total Fertility Rates under 1.3 raised the possibility of dramatic, rapid population aging as well as population decline. In an analysis of recent trends, we find, however, a widespread turn-around in so-called “lowest-low” fertility countries. The reversal

ObjectiveTo use publicly available secondary data to assess the impact of Brazil's Family Health Program on state level infant mortality rates (IMR) during the 1990s.DesignLongitudinal ecological analysis using panel data from secondary sources. Analyses controlled for state level measures of access to clean water and sanitation, average income, women's literacy and fertility, physicians and nurses per 10 000 population, and hospital beds per 1000 population. Additional analyses controlled for immunisation coverage and tested interactions between Family Health Program and proportionate mortality from diarrhoea and acute respiratory infections.Setting13 years (1990–2002) of data from 27 Brazilian states.Main resultsFrom 1990 to 2002 IMR declined from 49.7 to 28.9 per 1000 live births. During the same period average Family Health Program coverage increased from 0% to 36%. A 10% increase in Family Health Program coverage was associated with a 4.5% decrease in IMR, controlling for all other health determinants (p<0.01). Access to clean water and hospital beds per 1000 were negatively associated with IMR, while female illiteracy, fertility rates, and mean income were positively associated with IMR. Examination of interactions between Family Health Program coverage and diarrhoea deaths suggests the programme may reduce IMR at least partly through reductions in diarrhoea deaths. Interactions with deaths from acute respiratory infections were ambiguous.ConclusionsThe Family Health Program is associated with reduced IMR, suggesting it is an important, although not unique, contributor to declining infant mortality in Brazil. Existing secondary datasets provide an important tool for evaluation of the effectiveness of health services in Brazil.

From the *Male Fertility Laboratory, Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel; †IVF Unit, Department of Obstetrics and Gynecology, Rabin Medical Center, Petah Tikva, Israel; ‡IVF Unit, Herzliya Medical Center, Herzliya-on-the-Sea, Israel; and § ...

Reactive oxygen species (ROS) have a role in the modulation of gamete quality and gamete interaction. Generation of ROS is inherent in spermatozoa and contaminating leukocytes. ROS influence spermatozoa, oocytes, embryos and their environment. Oxidative stress (OS) mediates peroxidative damage to the sperm membrane and induces nuclear DNA damage. ROS can modulate the fertilizing capabilities of the spermatozoa. There is extensive literature on OS and its role in male infertility and sperm DNA damage and its effects on assisted reproductive techniques. Evidence is accumulating on the role of ROS in female reproduction. Many animal and human studies have elucidated a role for ROS in oocyte development, maturation, follicular atresia, corpus luteum function and luteolysis. OS-mediated precipitation of pathologies in the female reproductive tract is similar to those involved in male infertility. OS influences the oocyte and embryo quality and thus the fertilization rates. ROS appears to play a significant role in the modulation of gamete interaction and also for successful fertilization to take place. ROS in culture media may impact post-fertilization development, i.e. cleavage rate, blastocyst yield and quality (indicators of assisted reproduction outcomes). OS is reported to affect both natural and assisted fertility. Antioxidant strategies should be able to intercept both extracellular and intracellular ROS. This review discusses the sources of ROS in media used in IVF–embryo transfer and strategies to overcome OS in oocyte in-vitro maturation, in-vitro culture and sperm preparation techniques.

The fertilization and activation of fishoocytes are vital, but unfortunatelyoverlooked, processes in fisheries research.This paper sets out to review our presentunderstanding of these important events inteleost fish and, drawing comparisons withmammalian research, to highlight areas in whichresearch effort is urgently required. Presently, the commercial culture of manyimportant freshwater, but especially marine,teleosts is beset by problems associated withfertilization, hatching and early embryonicdevelopment. These problems have beenparticularly acute in certain species leadingto the application of spawning inductiontechnologies in an effort to optimizeproduction. Increased knowledge of theprocesses of egg activation and fertilizationin these groups of fish is likely to makesignificant contribution to commercialaquaculture. Studies of a wide variety ofanimal and plant species has demonstrated thatdevelopment at fertilization is triggered by anincrease in intracellular Ca2+concentration within the egg that occurs aseither a single transient or a series ofdistinctive oscillations depending upon thespecies under investigation. This increase inintracellular Ca2+ activates the egg andalso appears to play an important role in laterembryonic development. Teleost reproductivestrategies and more importantly, teleostoocytes and spermatozoa, exhibit a remarkablevariety of adaptations. Currently, studies ofegg activation in teleosts are confined tolaboratory species such as medaka Oryziaslatipes and zebrafish Brachydanio rerio.Nevertheless, even between these two species,although an increase in intracellular Ca2+appears to be the trigger in both cases, themechanism of Ca2+ release may be quitedifferent. Activation in medaka is initiatedonly through direct contact with conspecificsperm, suggesting the involvement of asperm-specific factor, while zebrafish eggsappear to require only contact with theexternal spawning medium. In view of the highlyvariable fertility rates evident in manycommercially cultured teleosts, it could bevery rewarding to investigate the mechanism ofegg activation in representative teleost groupsusing the findings and theories emerging fromother animal groups as a starting point. Inorder to successfully conduct such aninvestigation, it will be necessary to employ acombination of physiological, molecular andrecombinant approaches.