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Background: The possible impact of interpregnancy interval (IPI) on perinatal outcomes has long been studied, however, a definition of the optimal interval is still not clear. Both short and long IPIs have been associated with obstetrical syndromes and short and long-term complications. In this study, we sought to explore the impact of IPI on the hazard for neoplasm of the offspring, thus contribute to the present literature in determining the preferred birth spacing. Objective: We aim to investigate the association between short and long IPIs and the hazard for childhood neoplasm of the offspring. Methods: A population-based retrospective cohort analysis comparing offspring neoplasm hazard following three different IPIs. Exposure was defined as short (<6 months), or long (>60 months) IPIs, whereas intermediate IPI (6 months = 60 months) served as the comparison group. The study included singleton live births in a tertiary regional hospital between 1991 and 2014. Offspring were followed for 18 years, and all hospitalization records for neoplasm diagnoses were collected. Kaplan–Meier survival curves were used for the cumulative incidence of neoplasm morbidity, and Cox proportional hazards models were used to control for confounders. Results: During the study period, 144,397 deliveries met the inclusion criteria. Of those, 18,947 (13.1%) occurred in women with short IPI, 114,012 (79%) in women with intermediate IPI, and 11,438 (7.9%) in women with long IPI. 61 benign neoplasms and 80 malignant neoplasms were registered in offspring born after long IPI. The total percentage of neoplasm were the highest in the long IPI group versus the intermediate and short IPI groups (malignant = 0.7%, 0.6%, 0.5% respectively, benign = 0.5%, 0.4%, 0.3% respectively). Controlling for maternal age, diabetes mellitus, preterm delivery, birth weight, smoking, cesarean section, and fertility treatments, long IPI was found to be independently associated with high hazard for long-term pediatric neoplasm related hospitalizations (adjusted HR 1.39, 95% CI 1.09, 1.77). Short IPI may be associated to decreased hazard for childhood neoplasms (adjusted HR 0.74, 95% Cl 0.59, 0.92). Conclusions: Long IPI is associated with a high hazard for childhood neoplasms, compared with intermediate and short IPIs. Short IPI may be associated with decreased hazard for childhood neoplasms. [ABSTRACT FROM AUTHOR]

Recent studies have reported an increased risk of autism among second-born children conceived <12 versus >36 months after the birth of a sibling. Confirmation of this finding would point to inter-pregnancy interval (IPI) as a potentially modifiable risk factor for autism. This study evaluated the relationship between IPI and autism spectrum disorder (ASD) risk in a Wisconsin birth cohort of 31,467 second-born children, of whom 160 resided in the study area and were found to have ASD at age 8 years. In adjusted analyses, both short (<12) and long (>84 month) IPIs were associated with a two-fold risk of ASD relative to IPIs of 24-47 months ( p < 0.05). The long IPI association was partially confounded by history of previous pregnancy loss. [ABSTRACT FROM AUTHOR]

Infant and child mortality rates have decreased substantially in Matlab, Bangladesh, as they have in many developing areas. We use data from the Matlab Demographic Surveillance System on nearly 94,000 singleton live births that occurred between 1987 and 2002 to investigate the extent to which the change in mortality over this period can be explained by changes in reproductive patterns and socio-economic characteristics. We estimate Cox proportional hazards models for four subperiods of infancy and childhood. Changes over time in reproductive patterns (maternal age, parity, and pregnancy spacing) and in the socio-economic characteristics we consider (e.g. maternal education, SES) explain between 10 and 40% of the decline in mortality rates. Changes in maternal education explain the largest portion of the reduction in infant and child mortality over time that we are able to explain, followed by reductions in the incidence of short interpregnancy intervals. In the other direction, decreases in fertility over time led to increases in the proportion of births that were first births, putting upward pressure on mortality. [ABSTRACT FROM AUTHOR]

Using high-quality longitudinal data on 125,720 singleton live births in Matlab, Bangladesh, we assessed the effects of duration of intervals between pregnancy outcomes on infant and child mortality and how these effects vary over subperiods of infancy and childhood and by the type of outcome that began the interval. Controlling for other correlates of infant and child mortality, we find that shorter intervals are associated with higher mortality. Interval effects are greater if the interval began with a live birth than with another pregnancy outcome. In the first week of the child's life, the effects of short intervals are greater if the sibling born at the beginning of the interval died; after the first month, the effects are greater if that sibling was still alive. Many relationships found are consistent with the maternal depletion hypothesis, and some with sibling competition. Some appear to be due to correlated risks among births to the same mother. [ABSTRACT FROM AUTHOR]

Background: There are no national data on the prevalence of breastfeeding during pregnancy (BDP) in the world. Also, there is no consensus for the BDP. Aim: The purpose was to determine the prevalence of breastfeeding status in pregnant mothers having children younger than 24 months of age and to evaluate the associated sociodemographic factors and characteristics of the last-born child and current pregnancy through two consecutive national health survey. Methods: Data from the 2012 and 2017 Jordan Family Health and Population Survey were merged. Individual, household, and community-level factors associated with BDP were analyzed by using complex sample multivariate logistic regression. Results: Two surveys enrolled 6,858 women having at least one child younger than 24 months and 8.8% (weighted count: 603) of them got pregnant also. Of the pregnant women, 8.9% continued breastfeeding their last-born children. Being younger than 12 months positively affected breastfeeding compared to last-born child aged 12-23 months. Multivariate analysis revealed that BDP was associated positively with wealth index (richest vs. poorest) and postnatal care for the last-born child within 2 months (presence vs. absence), whereas negatively with bottle use (presence vs. absence), traditional contraceptive methods (abstinence/withdrawn vs. modern, lactational amenorrhea vs. modern), short interpregnancy interval (months), and current pregnancy duration (months) in Jordan. Conclusions: The prevalence for BDP differs according to some maternal, last-born infant, and current pregnancy characteristics. Prospective cohort studies are necessary to evaluate the impact of BDP on "mother, last-child, and future-child," and to detect the duration and prevalence of BDP in different countries.

Background: To examine whether induced abortion increases the risk of low birthweight in subsequent singleton live births., Methods: Cohort study using the Danish Medical Birth Registry (MBR), the Hospital Discharge Registry (HDR), and the Induced Abortion Registry (IAR). All women who had their first pregnancy during 1980-1982 were identified in the MBR, the HDR, and the IAR. We included all 15,727 women whose pregnancy was terminated by a first trimester induced abortion in the induced abortion cohort and 46,026 women whose pregnancy was not terminated by an induced abortion were selected for the control cohort. All subsequent pregnancies until 1994 were identified by register record linkage., Results: Low birthweight (<2500 g) in singleton term live births occurred more frequently in women with one, two, three or more previous induced abortions, compared with women without any previous induced abortion of similar gravidity, 2.2% versus 1.5%, 2.4% versus 1.7%, and 1.8% versus 1.6%, respectively. Adjusting for maternal age and residence at time of pregnancy, interpregnancy interval, gender of newborn, number of previous spontaneous abortions and number of previous low birthweight infants (control cohort only), the odds ratios (OR) of low birthweight in singleton term live births in women with one, two or more previous first trimester induced abortions were 1.9 (95% CI: 1.6, 2.3), and 1.9 (95% CI: 1.3, 2.7), respectively, compared with the control cohort of similar gravidity. High risks were mainly seen in women with an interpregnancy interval of more than 6 months., Conclusions: The findings suggest a positive association between one or more first trimester induced abortions and the risk of low birthweight in subsequent singleton term live births when the interpregnancy interval is longer than 6 months. This result was unexpected and confounding cannot be ruled out.

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).

The authors studied the effects and population-level impact of short (< or = 12 months) interpregnancy intervals on the risks for low (<2.5 kg) birth weight and preterm (<37 weeks) delivery of liveborn singleton infants to US African American, Mexican, Native American, non-Hispanic white, and Puerto Rican mothers (n = 4,841,418) from 1989 to 1991. Statistical analyses were done by using the Mantel-Haenszel correlation statistic chi-square test and logistic regression. The proportion of livebirths associated with < or =12-month interpregnancy intervals was the lowest among non-Hispanic whites (18.5%, 95% confidence interval 18.5-18.5) and the highest among Native Americans (29.7%, 95% confidence interval 29.2-30.2). As compared with mothers with >12-month intervals, mothers with <6-month intervals had an approximately 50% to 80% increased risk of very low (<1.5 kg) birth weight delivery and a 30% to 90% increased risk of very preterm (<32 weeks) delivery. Logistic regression analyses showed that the adverse effects of short intervals were reduced by about 10% but remained for the most part significant after controlling for potential confounding by maternal age, education, parity, marital status, prenatal care, smoking, and previous preterm delivery.

Weaning of human children is a complex process involving the introduction of non-breast-milk foods, reduction in suckling activity, and eventual termination of breast feeding. Because the choice of strategies for each component of the weaning process depends on the operating environmental constraints, reproductive demands on women, and prevailing levels of infant and weanling mortality, it is appropriate to examine weaning practices as human adaptive strategies. Here, I examine the structure of weaning and maternal attitudes toward weaning among nomadic Turkana pastoralists from the perspective of human adaptation. Using retrospective and prospective data on breast feeding, the use of non-breast-milk foods, and the cessation of breast feeding. I identify ideal strategies as those defined by Turkana women. Real behavior in relation to weaning, however, deviates considerably from the ideal, and this deviation reflects adaptive responses to nutritional and disease risks to infants. Particular attention is given to problematic aspects of weaning practices in Turkana, such as premature introduction of non-breast-milk foods and abrupt termination of breast feeding, which have been shown to contribute to high infant and weanling mortality in populations in developing countries. These practices have evolved from the dual caretaking and childbearing role of women and the necessity of reconciling the needs of the breast-feeding child with the demands of the next pregnancy. As such, they represent rational strategies for enhancing reproductive success in this and other similarly stressful environments.

The relationship between spontaneous and induced abortions and breast cancer risk was analyzed using data from a case-control study conducted between June 1991 and February 1994 in 6 Italian centers on 2,569 histologically confirmed incident breast cancer cases and 2,588 controls admitted to hospital for a wide range of acute, non-neoplastic, non-hormone-related diseases. One or more abortions were reported by 31% of cases and 32% of controls, corresponding to a multivariate odds ratio (OR) of 1.0 (95% confidence interval [CI], 0.8-1.1). No trend in risk was observed with increasing number of total abortions or spontaneous and induced abortions separately. No significant relationship was found between the risk of breast cancer and history of spontaneous or induced or total abortions in separate strata of age at diagnosis, number of children, time of abortion in relation to first birth and family history of breast cancer. When abortion was the outcome of the first pregnancy, the OR was 1.2 for spontaneous and 1.3 for induced abortion, in relation to women with birth as outcome of the first pregnancy, and 1.0 and 1.1, respectively, when the reference category was nulligravidae. Thus, our results indicate a lack of association between induced and spontaneous abortions and breast cancer risk.

In this study we assume that fertility decisions are made one birth at a time and use longitudinal data collected from 401 married couples over a two-year period to explore how having a child affects two types of fertility motivation and three types of fertility desires. Using a series of five constrained multiple regression analyses, we tested the effects of two childbearing variables on these five types of motivation and desires in the context of a large set of control variables also hypothesized to affect fertility motivation and desires. The results demonstrate that the childbearing variables have a substantial effect in all five regression models. Specific findings indicate that childbearing stimulates greater positive motivation for childbearing and an increase in the number of children desired. Although this situation would appear to create a positive feedback loop in which each child born further increases the motivation and desire for children, the findings also suggest three different mechanisms whereby childbearing causes a counterbalancing regulation of that loop. These mechanisms include a negative motivation mechanism, a satiation mechanism, and a delay mechanism. The effect of these mechanisms on the termination of childbearing is considered in conjunction with a fourth mechanism, the achievement of desired family size.

The relationship between breast-feeding and subsequent pregnancy in East Bhutan is examined, against the background of local attitudes to family planning. Ninety-eight mothers who had given birth 30-36 months earlier were interviewed. Semisolid supplementary feeding was introduced at a median age of 3 months. Median total duration of breast-feeding was 28 months, and day and night breast-feeding on demand was continued throughout. Median duration of postpartum amenorrhoea was 12 months, and was associated with the timing of the introduction of supplementary foods. There was a significant association between the occurrence of a subsequent pregnancy and early termination of breast-feeding. The relationships between breast-feeding pattern and pregnancy interval are complex, and their relative influence changes with time. During the first year postpartum, infertility during lactational amenorrhoea is important. During the second year there is a strong negative effect on lactation from the next pregnancy. The only important reason for ceasing to breast-feed within 2 years seems to be a new pregnancy.

Fertility is affected by the age of the female partner, but not that of the male partner, in the age ranges within which most attempts at conception occur. However, the literature on the effect of the smoking status of each partner is inconclusive. As part of a longitudinal study representative of all people born in Britain in 1958, 11,407 people were interviewed in 1991, of whom 3,132 female and 2,576 male cohort members had had or fathered at least one pregnancy. The outcome measure was the time to pregnancy of the first pregnancy (live births only), and the antecedent variables were the cohort member's age at that time and both partner's smoking habits and educational levels. Unadjusted analysis demonstrated that both the time to pregnancy and clinical subfertility were associated with higher maternal but not paternal age and with the smoking habits and educational levels of both parents. Multivariate analysis showed that paternal smoking failed to enter the model if the educational variables were also included. Findings were similar in the two separate analyses on male and female cohort members. This study confirms previous findings on the relative importance of maternal and paternal age in this age range. Maternal smoking affects fertility, but earlier reports of an apparent effect of paternal smoking may be due to confounding with socioeconomic status.

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.

Among 200 mothers interviewed in St. Lucia, 82.5% described their pregnancy as unintended and 44% as unwanted; 80% of women having an intended pregnancy and 94.6% having an unintended pregnancy were unmarried and 18.5% were teenagers. Mothers of unintended pregnancies were significantly younger, were of significantly higher parity and had begun sexual relations at a significantly earlier age than mothers of intended pregnancies; and, unlike mothers of planned pregnancies, their desired interpregnancy interval was significantly longer than the actual interval. These results and the sporadic and ineffective use of contraception in St. Lucia emphasize the need for improvements in fertility regulation in that country.

Objective: To examine the relationship of subfertility with miscarriage, low birth weight, and preterm delivery., Design: Comparison of time to pregnancy distributions between pregnancies that had different outcomes. Three comparisons were made: (a) miscarriages with live births; within live births, (b) low birth weight infant (up to 2,500 grams) or not low birth weight; (c) preterm birth (37 weeks or less) or not preterm. Cox regression was used to adjust for covariates., Population: All first pregnancies were analyzed from the National Child Development Study, a large survey of young adults aged 33 years, which is nationally representative of the British-born population., Main Outcome Measures: The distribution of the time taken to conceive (time to pregnancy), miscarriage, birth weight, and preterm delivery., Results: Pregnancies that ended in miscarriage tended to take 23% longer to conceive, after adjustment for the other variables. Pregnancies that resulted in preterm delivery tended to take 15% longer to conceive. There was no statistically significant association with low birth weight., Conclusions: Delay in time to conception is a risk factor for poor obstetric outcome, irrespective of medical intervention.

This study examines the effects of birth order and interpregnancy interval on birthweight, gestational age, weight-for-gestational age, infant length, and weight-for-length in a sample of 2063 births from a longitudinal study in the Philippines. First births are the most disadvantaged of any birth order/spacing group. The risks associated with short intervals (< 6 months) and high birth order (fifth or higher) are confined to infants who have both attributes; there is no excess risk associated with short previous intervals among lower-order infants, nor for high birth order infants conceived after longer intervals. This pattern is observed for all five birth outcomes and neonatal mortality, and persists in models that control for mother's age, education, smoking, family health history and nutritional status. Since fewer than 2% of births are both short interval and high birth order, the potential reduction in the incidence of low birthweight or neonatal mortality from avoiding this category of high-risk births is quite small (1-2%).

The authors tested the proposition that among humans (1) differences in lactational duration result in differences in costs of reproduction even under rich nutritional conditions; and (2) elimination of factors postulated to favor male-biased parental care will be reflected in elimination or reversal of sex-biased care. To do so, the authors examined the relationship between lactactational duration and fertility among Hutterites, a communal-living human population in which the levels of nutritional resources and fertility are high, breast feeding is the norm, contraceptive use is limited, and the collective social and economic system results in low resource variance among individuals. The authors demonstrate that even under good nutritional conditions, duration of nursing was a significant predictor of the length of time to next pregnancy and that nursing continued to suppress fertility after the resumption of menses. Moreover, the authors find that daughters were nursed longer than sons, leading to a longer interval to next pregnancy. The authors examine this uncommon, but not unique, finding of female-biased human parental care in the light of Hutterite social structure, and they explore the consistency of this finding with the most applicable models of parental investment.

Which adolescent mothers are most likely to become pregnant soon after their first delivery? This study identifies and explores selected background, pregnancy, and postpartum predictors of short-interval repeat pregnancy among urban Mexican adolescents who were single when they conceived their first pregnancy. Of 137 adolescents followed until their second postpartum year, 26 had short-interval repeat pregnancies. These pregnancies were most likely to occur if the teenager was married or in consensual union by 5 months postpartum, was not using an IUD, and had a mother who had been an adolescent mother. Being married or in consensual union postpartum was, in turn, predicted by positive reactions of the adolescent and her partner during the first pregnancy. Nonuse of IUD was more likely if the adolescent had left school prior to pregnancy, did not receive support from her partner during the first pregnancy, and had not obtained an IUD before hospital discharge after first delivery. Adolescents whose mothers had been teen mothers came from more disadvantaged families.

In order to learn the natural expectancy period of first pregnancy as well as the influences of some biosocial variables, a clinical-retrospective study was performed within 1120 gravida I women. All of them attended the major institutes of health care in Mexico City (IMSS, ISSSTE, SS and DDF). Data were obtained by means of predetermined questions from subjects after the first postpartum hours. None of them had previously used any contraceptive method. Results showed age at the first pregnancy: 21.6 +/- 3.8 (years); gestational interval 22.1 +/- 19.9 (months) and a 67% achievement rate the following twelve months of sexual activity. Eutocia was seen in 54% of these population and significant linear correlation was attained between age of the patient and the gestational interval. It seems that this is the first information regarding the fertility critical period within our society.

This is a report on unintended conception and unwanted fertility in Gondar, Northwestern Ethiopia. The purpose of the study was to explore the extent of the problem and to inquire whether there is a need for fertility regulation. To this end, relatively numerous questions on reproductive history of women aged 15-49 have been raised. Results showed that the proportion of abortion to delivery was 0.3984 to 0.6016 and the ratio of unintended conception to intended conception was 0.4043 to 0.5957. The proportion of unwanted fertility to wanted was 0.4099 to 0.5901. Mean desired interpregnancy interval was substantially higher than actual interpregnancy interval. The relatively high rate of abortion, high proportion of unintended conception and unwanted fertility combined with the wide difference between desired interpregnancy interval and current interpregnancy interval all point to the need for a policy that increases the capacity to regulate fertility.

To identify and quantify risk factors for preterm and term low birthweight (LBW) we conducted a hospital-based case-control study, linked with a population survey in Ahmedabad, India. The case-control study of 673 term LBW, 644 preterm LBW cases and 1465 controls showed that low maternal weight, poor obstetric history, lack of antenatal care, clinical anaemia and hypertension were significant independent risk factors for both term and preterm LBW. Short interpregnancy interval was associated with an increased risk of preterm LBW birth while primiparous women had increased risk of term LBW. Muslim women were at a reduced risk of term LBW, but other socioeconomic factors did not remain significant after adjusting for these more proximate factors. Estimates of the prevalence of risk factors from the population survey was used to calculate attributable risk. This analysis suggested that a substantial proportion of term and preterm LBW births may be averted by improving maternal nutritional status, anaemia and antenatal care.

Lactational amenorrhea plays an important role in child spacing. Recent research has led to a consensus regarding the status of lactational amenorrhea as a method of family planning. This is currently referred to as the lactational amenorrhea method. Research priorities were to field test the lactational amenorrhea method and define the factors that influence lactational amenorrhea and the interface between the lactational amenorrhea method and other family planning methods.

In many regions of the world, women breastfeed one child while pregnant with the next. Among rural Guatemalan women participating in a nutrition-supplementation trial, lactation overlapped with pregnancy in 253 of 504 (50.2%) of the pregnancies. For cases where overlap occurred, 41.4% continued to breast-feed into the second trimester and 3.2%, in the third trimester. The maternal and fetal responses to the energetic stresses of overlap and of the duration of the recuperative (nonpregnant, nonlactating) interval were assessed. Overlap resulted in increased supplement intake. Short recuperative periods (less than 6 mo) resulted in increased supplement intake and reduced maternal fat stores. The energetic stresses of overlap and short recuperative periods did not significantly affect fetal growth. The mother appears to buffer the energetic stress, protecting fetal growth. This research demonstrates that evidence of depletion of maternal nutrient stores caused by a demanding reproductive history is found when reproductive stress is characterized adequately.

Subsequent pregnancies in mothers of a birth cohort from Pelotas, Southern Brazil, were studied in relation to maternal and socio-economic factors. Within about 3 1/2 years of the cohort child's birth, 39% of mothers had experienced at least one further pregnancy. This proportion decreased with increasing maternal age, years of schooling and family income. A U-shaped trend was observed with respect to parity. Mothers who had delivered the cohort child by caesarean section were also less likely to have another pregnancy within that time. Logistic regression analysis showed that each of these factors remained significantly associated with further pregnancies after controlling for the remaining variables. Analysis of the first subsequent pregnancy showed that a high proportion of mothers had not wanted the pregnancy. Unwanted pregnancies were also significantly associated with older women, low educational status, higher parity and low family income.

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.

In diabetic women investigations have been performed covering the clinical consequences of intrauterine contraception and the influence on glucose and lipid metabolism of oral contraceptives. Insertion of copper-T intrauterine contraceptive devices in insulin-dependent diabetic women resulted in accidental pregnancy rates and total continuation rates after 12 months which were at the same levels as in non-diabetic women. No differences were observed in the maximum depth of corrosion or in the constitution of the corrosion products. The glucose tolerance as well as the serum lipoprotein levels remained unchanged when low-dose hormonal compounds were administered to women with a previous gestational diabetes. In insulin-dependent diabetic women it was found, that the use of oral contraceptives containing natural oestrogen may not give rise to difficulties with the diabetes control or disturbance in the lipid metabolism.

The length of the interval from last live birth to the subsequent pregnancy was studied for 121 contraceptive pill acceptors who were in postpartum amenorrhea at the time of acceptance and 121 matched nonacceptors in a prospective study in Matlab, Bangladesh. Half of the pill acceptors discontinued use within seven months, and as a group the pill acceptors had a significantly shorter interval to the next pregnancy than the matched nonacceptors. These findings suggest that unless continuation rates can be improved, it is better not to encourage women in rural Bangladesh to start the contraceptive pill during postpartum amenorrhea.

Conception-waits were studied retrospectively in 1,403 fertile oral contraceptive users who had stopped medication in order to conceive, and in 4,477 controls who stopped using other contraceptives. The proportion of pill users who conceived in the first month was 30% less than the others, but by the third month this difference had disappeared. There was no excess of long conception-waits in the oral contraceptive group nor any evidence for a cyclic return of fertility in them. There was a highly significant interaction between pill use and age, older women having a greater degree of temporary reduction in conceptions shortly after stopping the pill. There was also an interaction involving age and duration of use. In women who had used the pill for a short time, there was little age-effect, and in younger women there was little effect of the duration of use. Older women who had used the pill for several years, however, had a marked temporary reduction in fertility on stopping it.