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At least 19 recordsLinked to original sources
PubMed2001

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.

Female↗
PubMed1990

Time to pregnancy--a model and its application.

Biological fertility is poorly measured by the number of children born in industrially advanced societies. The time elapsing from when a couple decides to have a child to clinically recognizable pregnancy is a useful alternative. Time to pregnancy can be collected in broad categories in large samples. A model for condensing important information from such data is presented, which fits several large samples of reported waiting times. It is shown that multiparous women conceive more quickly than primiparous women.

Birth Intervals↗
PubMed2005

Six component intervals of nonproductive days by breeding-female pigs on commercial farms.

Of 105 swine herds using a production record system for breeding female pigs, 95 farms were used to analyze nonproductive female days (NPD), the six component intervals of NPD, and related measurements. The NPD was defined as the days when mated gilts and sows were neither gestating nor lactating, and it was calculated by summing the six component intervals in the average mated female inventory. The mean NPD was 57.9 d (SD = 20.5), and the proportions of six component intervals of gilt first-mating-to-pregnancy interval, gilt first-mating-to-culling interval, unmated weaning-to-culling interval, weaning-to-first-mating interval, sow first-mating-to-pregnancy interval, and sow first-mating-to-culling interval were 9.24, 7.82, 6.85, 27.9, 18.9, and 29.3%, respectively. Farms in the upper 25th percentile of the ranking for number of pigs weaned.mated female(-1).yr(-1) were designated as 25 high-performing farms. The remaining farms were designated as an ordinary farm group for comparisons. High-performing farms had 21.1 d fewer NPD, and five of the six component intervals were lower compared with the ordinary farms (P < 0.05). Regression analyses indicated that the number of litters.mated female(-1).yr(-1) increased by 0.07 in both farm groups as NPD decreased every 10 d. Fewer NPD were correlated with a higher percentage of multiple matings during estrus (P < 0.05) but were not correlated with removal risk and replacement risk in both farm groups. The average parity of culled females was negatively correlated with NPD in the ordinary farm group, and the average farrowed parity was positively correlated with NPD in the high-performing farm group (P < 0.01). Decreasing each component interval of the NPD six components is critical to increasing herd productivity. A high percentage of multiple matings during estrus and appropriate culling management may be key factors to decrease NPD.

Animal Husbandry↗
PubMed2005

Fecundity and pregnancy outcome in a cohort with sickle cell-haemoglobin C disease followed from birth.

OBJECTIVE: To compare pregnancy outcome in sickle cell-haemoglobin C (SC) disease with that in homozygous sickle cell (SS) disease and age-matched controls with a normal haemoglobin (AA) genotype. DESIGN: A cohort study followed from birth. SETTING: Sickle Cell Clinic, University Hospital and other Jamaican hospitals. POPULATION: Ninety-five pregnancies in 43 patients with SC disease, 94 pregnancies in 52 patients with SS disease and 157 pregnancies in 68 controls. METHODS: Systematic review of all pregnancies occurring in sample population. Kaplan-Meier analysis for interval to first pregnancy, and the t test, chi2 test or Fisher's exact test as appropriate; correction was made for multiple testing and multiple linear regression was used for analysis of determinants of birthweight. MAIN OUTCOME MEASURES: Age at menarche, interval to first pregnancy, outcome of pregnancy, maternal complications and possible predictors of low birthweight. RESULTS: Menarche was marginally delayed in SC disease compared with AA controls (median age 13.7 vs 13.0 years, P= 0.02) but age at first pregnancy was similar (median age 22.5 vs 20.1 years, P= 0.32). Pregnancy outcome in SC disease did not differ from AA controls but compared with SS disease there were marginally fewer miscarriages, more live deliveries and greater birthweight. The prevalence of pregnancy-induced hypertension, pre-eclampsia, antepartum or postpartum haemorrhage in SC disease did not differ from AA controls but the prevalence of sickle-related complications was similar to SS disease. CONCLUSIONS: Contrary to some claims, pregnancy outcome in SC disease is generally benign compared with SS disease.

Adolescent↗
PubMed2004

Outcome of pregnancy in homozygous sickle cell disease.

OBJECTIVE: Previous reports on pregnancy in homozygous sickle cell (SS) disease are biased by hospital-based, more severely affected subjects and may have underestimated recurrent early pregnancy losses. We report pregnancy outcome in a representative sample of SS subjects subsequently referred to as "subjects" or "sickle cell subjects," and matched normal controls followed from birth. METHODS: The outcomes of 94 pregnancies in 52 subjects and 157 pregnancies in 68 controls followed in a cohort study from birth are presented. Outcome measures included the age at menarche, interval to first pregnancy, outcome of pregnancy, and maternal complications. Possible predictors of low birth weight are assessed. Outcomes were compared by the Kaplan-Meier analysis for interval to first pregnancy and by Student t test, chi(2) test, or Fisher exact test, as appropriate. Correction was made for multiple testing, and multiple linear regression was used for analysis of birth weight. RESULTS: Compared with controls, SS subjects had later menarche (median age 15.4 versus 13.0 years) and first pregnancy (median age 23.7 versus 20.1 years), and more spontaneous abortions (36% versus 10%). Babies of SS subjects had a lower gestational age (P <.001) and lower birth weight (P <.001), the latter being significantly affected by sickle-related events in pregnancy. There was no difference in pregnancy-induced hypertension, preeclampsia, or antepartum or postpartum hemorrhage, but a retained placenta was marginally more common in SS subjects (Fisher exact test, P =.007 after adjustment for multiple testing). Two SS subjects died, a mortality rate of 2.1%. CONCLUSION: The increased fetal loss and maternal morbidity in mothers with homozygous sickle cell disease is confirmed. LEVEL OF EVIDENCE: II-2

Abortion, Spontaneous↗
PubMed1999

Why do cohabiting couples marry? An example of a causal event history approach to interdependent systems.

The purpose of this paper is to demonstrate a causal approach to interdependent systems based on two empirical investigations. These examples demonstrate 1) the study of two highly interdependent processes: entry into first marriage as the dependent process and the process of first birth/first pregnancy as the explaining one; 2) an interdependence occurring mainly in a very specific phase of individuals' lives (i.e., during the period of first family formation); 3) the involvement of time lags between cause and its effect (e.g., time until detection of conception); and 4) the highly dynamic character of an unfolding effect over time (i.e., the effect of first pregnancy/first birth on first marriage strongly depends on the progress of pregnancy and the time since the birth has taken place).

Birth Intervals↗
PubMed2005

Sympathetic and T helper (Th)2 bias may ameliorate uterine fibroids, independent of sex steroids.

We propose that inadequate sympathetic bias and Th2 bias in the uterine environment contributes to the formation of fibroids, independent of the sex steroid status. We also propose that fibroids represent a modern maladaptation that partly results from decreasing exposure to seminal fluid, which contains catecholalmines, transforming growth factor beta1 (TGFbeta1), aldosterone, prostaglandins, and other factors that shift the uterine environment to sympathetic and T helper (Th)2 bias. Lower risk of fibroids is associated with pre-menarche, post-menopause, pregnancy, exposure to contraceptives, smoking, earlier age of first pregnancy, shorter interval since last pregnancy, higher parity, and non-obesity. These associations are currently attributed to alterations of sex steroids. However, the association may also be explained by the observation that pre-menarche, post-menopause, pregnancy, and smoking represent periods of sympathetic and Th2 bias. Furthermore, use of contraceptives, early age of first pregnancy, short interval since last pregnancy, high parity, abnormal pap smear, and non-obesity may represent surrogates for increased sexual activity and increased exposure to seminal fluid. Catecholalmines, aldosterone, TGF, and prostaglandins are among the seminal fluid components that promote sympathetic and Th2 bias. Vasectomized copulations protect against fibroids, an observation that undermines the steroid hypothesis and supports our hypothesis. The putative mechanism of action of uterine artery embolization (UAE) for fibroid treatment is starvation of blood supply, but the extensive collaterals that protect uterine perfusion would presumably also buffer against fibroid hypoperfusion. Instead, the sympathetic and Th2 responses to UAE-related ischemia may contribute to fibroid regression. A potential explanation for the association of fibroids with intrauterine devices may be a Th1 cell-mediated immune response to the foreign body, which may also enhance the contraceptive effect. Novel methods of preventing and treating fibroids by promoting sympathetic and Th2 shift through natural, pharmacologic, and neuromodulatory means are envisioned. Fibroids are likely a modern dysfunction given the high Darwinian fitness cost of fibroid-related infertility, and may be attributable to reduced intercourse frequency. Fibroids have been observed among animals in captivity that are presumably reproductively isolated.

Female↗
PubMed1981

Sexual development and fertility of Jamaican female patients with homozygous sickle cell disease.

Results of a questionnaire study of 91 Jamaican patients with homozygous sickle cell (SS) disease and 59 Jamaican control subjects of similar socioeconomic status indicated a mean delay of 2.3 years in age at menarche and of 3.9 years in age at first pregnancy in Ss disease. The mean interval between first sexual exposure and pregnancy was similar in the two groups. The delay in age at first pregnancy in SS disease resulted partly from the delay in puberty, but it also resulted from a further delay in first sexual exposure, with a mean interval between menarche and first sexual exposure of 2.6 and 4.4 years in control subjects and patients, respectively. Physical and social factors that related to this delay were reflected in the higher prevalence of casual unions in patients; this finding implied lesser sexual exposure. Although the similar interval between first sexual exposure and pregnancy did not suggest a lesser fertility in patients with SS disease, the number of infants born to patients with SS disease was less at all ages compared with Jamaican standards. This finding might reflect lesser fertility subsequent to the first pregnancy.

Adolescent↗
PubMed1994

Factors affecting number of prenatal care visits during second pregnancy among adolescents having rapid repeat births.

PURPOSE: To examine factors associated with the number of prenatal care visits during second pregnancy for adolescents having a short interval between pregnancies. METHODS: The sample includes all adolescents aged 13 to 17 years whose first pregnancy resulted in a birth at a regional medical center in southeastern North Carolina from January 1983 to December 1989 and who had a repeat pregnancy within 24 months which resulted in a birth. We abstracted data from medical records and birth certificates. We fit a negative binomial regression model to determine the effects of various factors on the number of prenatal care visits during second pregnancy. RESULTS: The number of prenatal care visits during the first pregnancy, poor first birth outcome, interval between first and second pregnancy, and care provided by health department staff during first pregnancy were all positively associated with number of prenatal care visits during second pregnancy when controlling for gestation age of second birth. Other independent variables in the model included maternal age, education, black race, and being unmarried at the time of second birth. CONCLUSIONS: Because prenatal care is important for healthy mothers and babies, adolescents should be encouraged to seek prenatal care early in the first pregnancy. This could be an important time to implement interventions aimed at increasing prenatal care utilization in this and subsequent pregnancies.

Adolescent↗
PubMed1982

Relation between morphologically abnormal spermatozoa and pregnancies obtained during a twenty-year follow-up period.

The clinical fertility of 1077 men investigated with semen analysis including detection of morphologically abnormal spermatozoa during the years 1950-52 was studied 20 years later using a questionnaire replied to by 785 (72.9%). There was a significant correlation (P less than 0.01) between increasing number of abnormal spermatozoa and decreasing chance of getting living children, but no relation to abortions and pathological pregnancies. Moreover, there was a significant correlation (P less than 0.01) to time-interval to first pregnancy. Median values for those obtaining living children was 25% abnormal spermatozoa compared with 28% for those not doing so. Up to 60% abnormal spermatozoa, fertility was not reduced, and the borderline between normal and reduced male fertility is therefore defined to be 60% morphologically abnormal spermatozoa.

Abortion, Spontaneous↗
PubMed1980

Sex of first child as a prognostic factor for breast cancer in young women.

In a study in upstate New York, incidence and survival rates of 317 young women (less than 45 years), diagnosed with breast cancer, were examined in relation to the sex of each woman's first offspring. While incidence of breast cancer was not found to be affected by the sex of the first child, prognosis was poorer when the first child was made (p less than 0.05). The authors examined the effect of stage at diagnosis, interval between first pregnancy and diagnosis and concurrent pregnancy at the time of diagnosis as factors other than sex of first offspring that might have an additional influence on survival. Among these, only interval had an effect, and it was of weak statistical significance (0.05 less than p less than 0.1). These findings regarding survival in relation to the sex of the offspring are opposite to those reported recently in France by Juret et al. (Lancet 1:415-416, 1978). Possible differences between the two studies which may account for the opposite findings are discussed.

Breast Neoplasms↗
PubMed1998

Development of a progestin-based estrus synchronization program: I. Reproductive response of cows fed melengestrol acetate for 20 days with an injection of progesterone.

We designed two experiments to determine the efficacy of an estrus control system in cows that combined long-term progestin exposure (20 d) with an acute increase in progesterone concentration. In Exp. 1, cows (n = 30) were fed either melengestrol acetate (MGA; .5 mg x cow(-1) x d(-1)) or ground ear corn (MGA carrier) for 20 d. On d -15 (last day of MGA feeding = d 0), cows were administered 25 mg of PGF2alpha to regress the corpus luteum (CL) and establish an environment conducive to the development of persistent follicles. To synchronously regress persistent follicles, cows fed MGA (n = 15) were injected with 200 mg of progesterone on d -2 (MGA-P), and the cows fed the MGA carrier were not treated (CONT; n = 15). Cows in the CONT group were artificially inseminated 12 h after detection of spontaneous estrus from d -20 to d 8. Estrus was observed, and all cows in the MGA-P group were artificially inseminated during the period of estrus synchronization (SYNC; d 1 to 8). No difference in conception rate was observed between treatments. In Exp. 2, postpartum cows (n = 113) received either the MGA-P (n = 56) or CONT (n = 57) treatment. More (P < .05) cows were observed in estrus during SYNC in the MGA-P (50%) than in the CONT (28%) group. Of the cows in the MGA-P group that were not observed in estrus during SYNC, 50% were in estrus for the first time 23 to 29 d after MGA withdrawal (SYNC2), suggesting that these cows ovulated without observable estrus during SYNC. Estrus was observed for the first time during SYNC2 in more (P < .05) cows in the MGA-P (25%) than in the CONT (7%) group. Conception rate at the synchronized estrus, pregnancy rate, and interval to first service and pregnancy were similar between treatments. We conclude that administration of MGA-P results in the synchronization and(or) induction of a fertile estrus in cows.

Administration, Oral↗
PubMedDate not supplied

Relation between spermatozoa motility and pregnancies obtained during a twenty-year follow-up period spermatozoa motility and fertility.

The clinical fertility of 1077 men with an infertility problem investigated with semen analysis including assessment of spermatozoa motility during the years 1950-52 was studied 20 years later using a questionnaire, replied by 785 (72.9%). Spermatozoa motility was assessed with a subjective method with four degrees--excellent, good, impaired and poor. There were significant correlations between better motility and number of living children (p less than 0.01) and to shortest time--interval to first pregnancy (p less than 0.001). Motility was not correlated to abortions and otherwise pathological pregnancies. With a poor motility there was still a fairly good chance of obtaining living children (32.7%) compared with 58.7% for an excellent motility), and it is therefore concluded, that assessment of spermatozoa motility is only suited for classification of slightly and modestly reduced male fertility, and not for classification of severely impaired fertility.

Abortion, Spontaneous↗