Month of birth related to fecundity and childlessness among contemporary women.

To determine the associations of fecundity and childlessness with month of conception and to find a causal mechanism for these associations, we reanalyzed some of our previous data according to the predictions of the seasonal optimal ripening oocyte (SOptRO) and seasonal preovulatory over-ripeness ovopathy (SPrOO) hypotheses. Prime and minor SOptRO months as well as high-risk, no-risk, and very high risk SPrOO months were defined on the basis of a priori knowledge of the existence of ovulatory and anovulatory seasons in mammals and of the general birth distribution in Europe. The month of birth was assessed among 899 mothers with three or more children and 388 childless women extracted from a 1% sample of the Austrian population. The women with three or more children were born in excess during the prime and less often during the minor SOptRO months (chi2 = 2.81; p = 0.045; relative risk = 1.16; 95% CI = 1.01-1.33). This is in line with the SOptRO predictions. The childless women were more frequently born during the high-risk SPrOO months compared to the no-risk months but less often during the very high risk months. The linear trend (chi2 = 8.43; p = 0.009) is in line with the SPrOO predictions. We suggest that fecundity and childlessness are dependent on the gradient of oocyte maturation reflected by mother's month of birth, which may modulate future constitution.

Over-ripeness ovopathy: a challenging hypothesis for sex ratio modulation.

Current hypotheses do not explain the concerns about sex ratio modulation at conception, birth or during life, and particularly about sex ratio reversal, e.g. at very young or advanced maternal age, during 'anovulatory seasons', among those of low socio-economic status, or induced by specific lifestyles, etc. These modulations are explained by the introduction of the ovopathy concept and inherent preferential fertilization of non-optimally matured oocytes by Y-bearing sperm. Non-optimal development and implantation of male-biased fetuses results in perennial loss of non-optimal, male-biased fetuses before and after birth. Accumulation of conceptopathology in extreme conditions entrains an increasing male to female ratio and ultimately a decreasing one, i.e. an 'inverted dose-response gradient' or 'dose-response fallacy'.

[Short pregnancy interval and reproductive disorders]. / Kort zwangerschapsinterval en voortplantingsstoornissen.

The cause of the 'borderline personality disorder' of Vincent van Gogh has been discussed in social-psychiatric terms related to so-called 'substitute children', born after the loss of a previous child. A biological-organic genesis, i.e. the very short birth interval of precisely one year between Van Gogh and his older brother appears to be a more plausible explanation. Personality disorders, which are part of the spectrum of schizophrenic disorders, seem to belong to the very broad 'continuum of reproductive casualties' and to be caused by non-optimal maturation of the oocyte during the postpartum restoration of the ovulatory pattern. This continuum occurs during each of the transitional stages of reproductive life in which the maturation of the oocyte is constrained and consists of chromosomal aberrations, (discordant) monozygotic twins, early and late foetal death, preterm births, intrauterine growth retardation, congenital abnormalities, perinatal and neonatal mortality, cot death, growth and mental defects, and finally, chronic or 'constitutional' diseases. Non-optimal maturation of the oocyte appears to be a risk factor for the reproductive casualties stated.

The secular trends in male:female ratio at birth in postwar industrialized countries.

Finnish investigators [Vartiainen et al. Environmental Chemicals and Changes in Sex Ratio: Analysis Over 250 Years in Finland. Environ Health Perspect 107:813-815 (1999)] presented the sex ratio of all newborn babies from 1751 to 1997 in order to evaluate whether Finnish long-term data are compatible with the hypothesis that the decrease in the ratio of male to female births after World War I and World War II in industrial countries is caused by environmental factors. They found an increase in the proportion of males from 1751 to 1920, which was interrupted by peaks in male births during World War I and World War II and followed by a decrease thereafter, similar to the trends in many other countries. The turning point of male proportion, however, preceded the period of industrialization and introduction of pesticides and hormonal drugs. Thus, a causal association between these environmental exposures and this decrease is unlikely. In addition, none of the various family parameters (e.g., paternal age, maternal age, age difference in parents, birth order) could explain the historical time trends. Vartiainen et al. concluded that at present it is unknown how these historical trends could be mediated. The postwar secular decline of the male:female ratio at birth is not an isolated phenomenon and parallels the decline of perinatal morbidity and mortality, congenital anomalies, and various constitutional diseases. This parallelism indicates a common etiology and may be caused by reduction of conceptopathology, as a correlate to increasing socioeconomic development. An inverted dose response or the dose-response fallacy due to vanishing male conceptuses explains the low sex ratios before World War I and World War II in newborns from black parents and from the lowest socioeconomic classes.

Season of birth and reproductive performance: an analysis of family reconstitutions of 800 women born in The Netherlands at the end of the 19th century.

BACKGROUND: Several studies have reported associations between season of birth and reproductive characteristics such as menarcheal age, fecundability, and twinning, but the results are inconsistent with respect to the location of high- and low-risk seasons. To assess whether this disagreement could be due to the use of populations from different geographic areas and time frames instead of different etiologic pathways, we investigated the season-of-birth dependency of a variety of reproductive outcomes within one time- and area-limited population. METHODS: In a historic follow-up study, the reconstituted families of 800 women born between 1873 and 1887 in or near Rotterdam, The Netherlands, were used to determine eight types of reproductive outcome: childlessness, interval to first pregnancy, pregnancy interval, stillbirth, neonatal death, postneonatal death, multiple birth, and gender of offspring. The relation of these outcomes with season of birth was modeled using cosinor functions with periods of 1 year or a half year. Data were analyzed by use of logistic regression or general estimation equations (GEE), dependent on whether outcomes could occur more than once per woman. RESULTS: Peaks in the model-based risks of reproductive failure were found within two small temporal ranges, January 1 to February 11 and July 1 to August 11 for all outcomes except gender. The picture did not change after controlling for known and possible risk factors, including age, offspring's birth cohort, and some social variables. CONCLUSIONS: This study reconfirms the idea that seasonal factors around conception or birth influence later reproductive characteristics. Observing the consistency of the location of high-risk seasons across a variety of outcomes, the explanation of season-of-birth dependency of different reproductive outcomes need not involve multiple etiological pathways.

Fecundity of daughters born after short, intermediate, or long birth intervals. An analysis of family reconstitutions from The Netherlands, late 19th-early 20th century.

In an historical cohort study, we compared the reproductive performances of women born after short (< 14 completed months), intermediate (21-32 completed months), and long (> 39 completed months) birth intervals. Of the initial study base, comprising family reconstitutions of 1,425 women born between 1873 and 1902 in or around Rotterdam (The Netherlands) and married before age 45, a large portion (data of 1,001 women born between 1888 and 1902) was uninformative because of (unintended) selection on birth control behavior. Among the remaining 424 women, those born after very short birth intervals (less than 1 year) showed higher likelihood of childlessness and stillbirth in the offspring than those born after intermediate intervals (adjusted odds ratios (OR) and 95%-confidence intervals: 7.7 [1.8-33.0] and 3.3 [1.3-8.3], respectively). The latter association, however, nearly disappeared after restriction to women whose preceding sibling lived at least 1 year. Women born after modestly short intervals (12-13 months) exhibited longer interpregnancy intervals. So did women born after long birth intervals, but this might well be attributable to intergenerational transmission of reproductive behavior. These results indicate that fecundability is reduced in women born after short birth intervals.

Conditions at conception in women with recurrent miscarriage.

In order to evaluate the role of conditions at conception in the risk of miscarriage, we sent 234 women with at least two consecutive miscarriages after conceptions from the same partner a short questionnaire asking for the birth dates of their mothers and their live or stillborn siblings and the occurrence of any maternal miscarriages. Complete information was provided by 186 respondents. Using matched logistic regression, we investigated whether these women were born more often than their siblings (total n = 578) to young (< or = 19 years) or relatively old (> or = 40 years) mothers or shortly after a preceding pregnancy (born within 1 year). We also evaluated whether they showed a different month-of-birth distribution. No increased odds ratios were found for young or advanced maternal age, or for short preceding birth intervals. However, relative to their siblings, cases showed a deviant month-of-birth distribution (p = 0.08) with a peak in (late) winter. These results indicate that low and high maternal age and short preceding birth intervals are not determinants of the risk of miscarriage in the daughter. They also suggest that there may be seasonally varying factors that prenatally influence the risk of miscarriage.

Seasonal variation in human fecundability.

Seasonality of effective fecundability was investigated in a cohort of 402 women born in or near Rotterdam, The Netherlands, between 1873 and 1887, and married before the age of 40 years. Applying a newly developed method allowing simultaneous control for inherent couple fecundability, numbers at risk of pregnancy, and multiple confounders, we found a trend towards higher fecundability during the first half of June and the first half of December (P = 0.06). Seasonality of effective fecundability appeared to be strongest for women who married at <20 years of age. Potentially important implications for the study of seasonality of adverse reproductive outcome are discussed.

Conditions at conception and risk of menstrual disorders.

In a case-control study, we evaluated the association of the risk of menstrual disorders with four periconceptional factors: short preceding interpregnancy interval (< 6 months), low (< or = 19 years) or high (> or = 40 years) maternal age at conception, and month of conception. We divided 919 women who had visited a fertility clinic between 1991 and 1995 into three categories: cases (with mean menstrual cycle length > or = 42 or < or = 21 days, or a variation of > or = 14 days between cycles, or amenorrhea, N = 294), controls (with cycles within a range of 25-35 days and variation < or = 7 days, N = 520), and intermediates (N = 105). A self-administrable questionnaire was mailed, asking for information about maternal reproductive history and age, and potential confounders such as smoking, exercise, and level of education. Response (77%) differed little among cases, intermediates, and controls. We found elevated risks for short pregnancy intervals [adjusted odds ratio (OR) = 2.04; 95% confidence interval (CI) = 1.04-4.02] and advanced maternal age (OR = 3.24; 95% CI = 1.27-8.30) but not for low maternal age (OR = 0.58; 95% CI = 0.11-3.14) (cases vs controls). We found similar effects for intermediates vs controls. The distribution of month of conception did not differ much from controls for both cases and intermediates. The results indicate that conception after short pregnancy intervals or at advanced maternal age increases the risk of menstrual disorders in daughters. The precise etiology is unclear, but it may lie in the quality of the oocyte at conception.

Seasonal variation in the prevalence of Down syndrome at birth: a review.

STUDY OBJECTIVE: Many studies on seasonality in Down syndrome (DS) have been performed and have come to different conclusions. It is suggested that seasonal variation in hormone production by the hypothalamus-pituitary-ovarian axis just before ovulation leads to seasonality in conception rates of DS. This study aimed to determine whether there is seasonal variation in the prevalence of DS at birth as a proxy for seasonality in DS at conception. DESIGN: All the English and Dutch articles on this topic were reviewed. Articles published between 1966 and January 1996 were traced by Medline, and by the reference lists. MAIN RESULTS: Twenty articles met the criteria for inclusion. Although seven of these studies reported seasonality in DS prevalence, no consistent seasonal pattern was found in DS at birth in these studies, or in the remaining studies. A seasonal pattern could not have been masked by the effects of maternal age, induced abortions, shortened gestation, or misclassification of DS. CONCLUSION: Seasonality in the prevalence of DS at birth does not exist. Evidence did not support the suggestion that DS occurrence is related to seasonality in hormone production.