Delayed time to pregnancy and associated factors among pregnant women attending antenatal care in bale zone administrative towns health facilities: multi-center cross-sectional study

BACKGROUND

The desire to conceive and become parents is a fundamental aspect of human life that carries immense personal, emotional, and societal significance. For many couples, achieving pregnancy represents a long-cherished dream, but the journey to parenthood is not always straightforward. The duration it takes to achieve the desired pregnancy can vary significantly among individuals and is influenced by many factors. This study explores the factors that influence the delayed time of pregnancy among women with naturally planned conception.

METHODS

An institutional-based cross-sectional study was conducted from May 1 to May 30, 2023, in public health facilities of Bale Zone administrative towns, Southeast Ethiopia. Using systematic random sampling, 388 women participated in the study and a pretested questionnaire was used to collect data. Bivariate logistic regression was done, and variables with p-values < 0.25 were exported to multivariable logistic regression, and a statistically significant association was declared at p-value < 0.05.

RESULTS

The study revealed delayed time to pregnancy was 18.6% with 95% (CI = 14.67-22.44%). Women's age ≥ 35, (AOR = 2.61; 95%, CI: 1.17-5.82), menstrual irregularity (AOR = 3.79; 95% CI: 1.98-7.25), and frequency of sexual intercourse/week (AOR = 2.15; 95% CI: 1.05-4.41) and women's sexual dysfunction before conception (AOR = 3.12, 95% CI: 1.62-6.01) were significantly associated factors with delayed time to pregnancy at p-value < 0.05.

CONCLUSION

The study revealed a substantial proportion of delayed time to pregnancy. This delayed time to pregnancy was associated with older maternal age, irregular menstrual cycles, coital activity per week, and the women's sexual dysfunction before pregnancy. Consequently, addressing delayed time to pregnancy requires a targeted approach, prioritizing initiatives such as raising awareness, fostering increased frequency of sexual activity per week, exploring interventions for women with irregular menstrual patterns, and challenges related to sexual dysfunction.

Sub-fecundity and associated factors among mothers with natural planned conception attending antenatal care service in Arba Minch Health Facilities

Background

Fecundity is a physiological ability to have children. The inability to get the desired child which was commonly caused by the prolonged time to conceive due to unwanted non-conception period increased from time to time. As a result, many couples are developing psychological, social, and economic problems and unstable life. However, information on fecundity status is limited in Ethiopia context. Therefore, this study aimed to assess the proportion of sub-fecundity and associated factors in Ethiopia context.

Methods

A health institution based cross-sectional study was conducted in Arba Minch health facilities from March 25 to April 25, 2020. By using a systematic sampling method, 539 mothers were selected for the study. Structured questionnaire was used for data collection. A binary logistic regression model was used to identify factors associated with the sub-fecundity. Variables with p-value <0.25 in the bi-variable logistic regression analysis were interred and checked for association in a multivariable logistic regression model. The level of statistical significance was declared at p-value <0.05.

Result

The proportion of sub-fecundity was 17.8% with 95%CI (14.8%-21.3%). Mothers’ age ≥ 30 (AOR = 2.54, 95%CI; 1.18–5.48), partners’ age ≥ 35 (AOR = 2.20, 95%CI; 1.01–4.75), coffee consumption of ≥ 4 cups/day (AOR = 2.93, 95%CI; 1.14–7.53), menses irregularity (AOR = 3.79 95%CI; 2.01–7.14) and coital frequency of 1day/week (AOR = 3.65, 95%CI; 1.47–9.05) were significantly associated with the sub-fecundity.

Conclusion

This study found that a substantial proportion of mothers were sub-fecund. Factors that contributed to the sub-fecundity were pre-pregnancy; mothers’ age, partners’ age, coffee drinking of ≥ 4 cups/day, coital frequency of 1day/week, and menses irregularity. Thus, efforts to prevent sub-fecundity should focus on awareness creation as to plan to conceive at early age, reducing coffee consumption, increasing days of coital frequency per week, and investigating and treating mothers with irregular menses.

Reproductive and obstetric outcomes in mildly and significantly underweight women undergoing IVF

RESEARCH QUESTION

What is the impact of low body mass index (BMI) on live birth rates and obstetric outcomes in infertile women treated with IVF and fresh embryo transfer?

DESIGN

This was a retrospective cohort study of infertile patients in an academic hospital setting who underwent their first oocyte retrieval with planned autologous fresh embryo transfer between 1 January 2012 and 31 December 2018. The primary study outcome was live birth rate. Secondary outcomes were IVF treatment and delivery outcomes. Underweight patients were stratified into a significantly underweight group (body mass index [BMI] <17.5 kg/m²) and a mildly underweight group (BMI 17.5-18.49 kg/m²), and were compared with a normal-weight group (BMI 18.5-24.9 kg/m²).

RESULTS

A total of 5229 patients were included (significantly underweight, 76; mildly underweight, 231; normal weight, 4922), resulting in 4798 embryo transfers. After oocyte retrieval, there were no significant differences between groups for total oocytes, mature oocyte yield and number of supernumerary blastocysts cryopreserved. Among women who had an embryo transfer, there were no significant differences in the live birth rates in significantly (31.0%, odds ratio [OR] 0.67, confidence interval [0.95, CI] 0.40-1.13) and mildly (37.7%, OR 0.95, CI 0.73-1.33) underweight patients compared with normal-weight patients (35.9%). Additionally, there were no statistically significant increased risks of preterm delivery, Caesarean delivery or a low birthweight (<2500 g) neonate.

CONCLUSIONS

Mildly and significantly underweight infertile women have similar pregnancy and live birth rates to normal-weight patients after IVF treatment. In addition, underweight patients do not have an increased risk of preterm delivery (<37 weeks), Caesarean delivery or a low birthweight neonate.

Female ponderal index at birth and idiopathic infertility

Epidemiological studies have demonstrated an increased risk of developing non-transmittable diseases in adults subjected to adverse early developmental conditions. Metabolic and cardiovascular diseases have been the focus of most studies. Nevertheless, data from animal models also suggest early programming of fertility. In humans, it is difficult to assess the impact of the in utero environment retrospectively. Birthweight is commonly used as an indirect indicator of intrauterine development. This research is part of the ALIFERT study. We investigated a potential link between ponderal index at birth and female fertility in adulthood. Data from 51 infertile and 74 fertile women were analysed. BW was on average higher in infertile women, whereas birth length did not differ between the two groups; thus, resulting in a significantly higher ponderal index at birth in infertile women. Ponderal index at birth has been identified as a risk factor for infertility. These results suggest the importance of the intra-uterine environment, not only for long-term metabolic health but also for fertility.

Waist circumference in relation to outcomes of infertility treatment with assisted reproductive technologies

BACKGROUND

Many studies have documented a lower likelihood of live birth with increasing body mass index among women undergoing assisted reproductive technology, but few have examined the association with waist circumference, an anthropometric measure that allows assessment of central adiposity.

OBJECTIVE

To examine the relation between baseline waist circumference and infertility treatment outcomes among women undergoing treatment with assisted reproductive technology.

MATERIALS AND METHODS

We followed up 264 women who underwent 445 assisted reproductive technology cycles for infertility treatment at the Massachusetts General Hospital between 2010 and 2017. Waist circumference was assessed at enrollment. We used cluster-weighted generalized estimating equation models to estimate the probability of live birth by tertiles of waist circumference (<77, 77-86, >86 cm), while accounting for multiple treatment cycles per woman and adjusting for age, race, smoking, infertility diagnosis, day 3 follicle-stimulating hormone, body mass index, and height.

RESULTS

Mean (standard deviation) waist circumference and body mass index were 83.6 (12.6) cm and 24.1 (4.3) kg/m², respectively. Waist circumference and body mass index were positively correlated (r = 0.69, P < .0001). Waist circumference was inversely related to the probability of live birth after adjusting for BMI and other confounders. The multivariable adjusted probability of live birth (95% confidence interval) for women in increasing tertiles of waist circumference were 53% (42-65%), 42% (32-53%), and 38% (28-50%) (P, trend = .04). When women were classified in joint categories of body mass index and waist circumference, women with a body mass index ≥25 kg/m² and a waist circumference ≥77 cm had the lowest live birth rate (38% [27-50%]), whereas women with a body mass index between 18.5 and 25 kg/m² and a waist circumference <77 cm had the highest (54% [42-66%]). The results were similar using different waist circumference cut-off values.

CONCLUSION

Waist circumference was inversely related to the probability of live birth among women undergoing assisted reproductive technology independently of body mass index.

Pregnancy and birth outcomes in couples with infertility with and without assisted reproductive technology: with an emphasis on US population-based studies

Infertility, defined as the inability to conceive within 1 year of unprotected intercourse, affects an estimated 80 million individuals worldwide, or 10-15% of couples of reproductive age. Assisted reproductive technology includes all infertility treatments to achieve conception; in vitro fertilization is the process by which an oocyte is fertilized by semen outside the body; non-in vitro fertilization assisted reproductive technology treatments include ovulation induction, artificial insemination, and intrauterine insemination. Use of assisted reproductive technology has risen steadily in the United States during the past 2 decades due to several reasons, including childbearing at older maternal ages and increasing insurance coverage. The number of in vitro fertilization cycles in the United States has nearly doubled from 2000 through 2013 and currently 1.7% of all live births in the United States are the result of this technology. Since the birth of the first child from in vitro fertilization >35 years ago, >5 million babies have been born from in vitro fertilization, half within the past 6 years. It is estimated that 1% of singletons, 19% of twins, and 25% of triplet or higher multiples are due to in vitro fertilization, and 4%, 21%, and 52%, respectively, are due to non-in vitro fertilization assisted reproductive technology. Higher plurality at birth results in a >10-fold increase in the risks for prematurity and low birthweight in twins vs singletons (adjusted odds ratio, 11.84; 95% confidence interval, 10.56-13.27 and adjusted odds ratio, 10.68; 95% confidence interval, 9.45-12.08, respectively). The use of donor oocytes is associated with increased risks for pregnancy-induced hypertension (adjusted odds ratio, 1.43; 95% confidence interval, 1.14-1.78) and prematurity (adjusted odds ratio, 1.43; 95% confidence interval, 1.11-1.83). The use of thawed embryos is associated with higher risks for pregnancy-induced hypertension (adjusted odds ratio, 1.30; 95% confidence interval, 1.08-1.57) and large-for-gestation birthweight (adjusted odds ratio, 1.74; 95% confidence interval, 1.45-2.08). Among singletons, in vitro fertilization is associated with increased risk of severe maternal morbidity compared with fertile deliveries (vaginal: adjusted odds ratio, 2.27; 95% confidence interval, 1.78-2.88; cesarean: adjusted odds ratio, 1.67; 95% confidence interval, 1.40-1.98, respectively) and subfertile deliveries (vaginal: adjusted odds ratio, 1.97; 95% confidence interval, 1.30-3.00; cesarean: adjusted odds ratio, 1.75; 95% confidence interval, 1.30-2.35, respectively). Among twins, cesarean in vitro fertilization deliveries have significantly greater severe maternal morbidity compared to cesarean fertile deliveries (adjusted odds ratio, 1.48; 95% confidence interval, 1.14-1.93). Subfertility, with or without in vitro fertilization or non-in vitro fertilization infertility treatments to achieve a pregnancy, is associated with increased risks of adverse maternal and perinatal outcomes. The major risk from in vitro fertilization treatments of multiple births (and the associated excess of perinatal morbidity) has been reduced over time, with fewer and better-quality embryos being transferred.

Relationship of maternal birth weight on maternal and neonatal outcomes: a multicenter study in Beijing

OBJECTIVE

Birth weight is an important indicator for childhood and adulthood diseases. Published studies lack information on the relative contribution of women's own birth weight to the course of her pregnancy, not only for maternal but especially to neonatal outcome. The aim of the study was to evaluate the relationship of maternal birth weight on maternal and perinatal complications during pregnancy.

STUDY DESIGN

Medical and obstetrical data were collected from 5479 women at 15 hospitals in Beijing, by a systemic cluster sampling survey conducted from 20 June 2013 to 30 November 2013. These women were categorized into five groups, according to their own birth weight: low birth weight (⩽2500 g, n=275), sub-optimal birth weight (2500 to 2999 g, n=1079), optimal birth weight (3000 to 3499 g, n=2590; 3500 to 3999 g, n=1085) and high birth weight (⩾4000 g, n=450). The occurrence of maternal and neonatal complications was recorded and compared among the groups. Statistical analysis was performed by SPSS 20.0 and values of P<0.05 were considered to be statistically significant.

RESULTS

Low maternal birth weight was associated with higher rates of gestational diabetes mellitus (χ²=21.268, P=0.006) and hypertensive disorders (χ²=10.844, P=0.028). The latter association was strongest in women with a pre-pregnancy body mass index above 25 kg m^-2. Low maternal birth weight was also associated with an apparently higher incidence of preterm labor (χ²=18.27, P=0.001) and hypertriglyceridemia (χ²=2.739, P=0.027) in pregnancy. An association between women with low birth weight and a significantly higher rate of small for gestational age infants (χ²=93.507, P<0.001) and low birth weight (χ²=36.256, P<0.001) was detected. High maternal birth weight was associated with an increased risk of pre-pregnancy overweight and obesity (P<0.001), as well as for large for gestational age infants (χ²=93.507, P<0.001) and macrosomia (χ²=72.594, P<0.001).

CONCLUSIONS

In our study, high or low maternal birth weight was strongly associated with maternal and perinatal adverse pregnancy outcomes. This suggests that by controlling the birth weight of female infants among the normal range, adverse outcomes may be decreased in the future and for the following generations.

Early-life disease exposure and associations with adult survival, cause of death, and reproductive success in preindustrial humans

A leading hypothesis proposes that increased human life span since 1850 has resulted from decreased exposure to childhood infections, which has reduced chronic inflammation and later-life mortality rates, particularly from cardiovascular disease, stroke, and cancer. Early-life cohort mortality rate often predicts later-life survival in humans, but such associations could arise from factors other than disease exposure. Additionally, the impact of early-life disease exposure on reproduction remains unknown, and thus previous work ignores a major component of fitness through which selection acts upon life-history strategy. We collected data from seven 18th- and 19th-century Finnish populations experiencing naturally varying mortality and fertility levels. We quantified early-life disease exposure as the detrended child mortality rate from infectious diseases during an individual's first 5 y, controlling for important social factors. We found no support for an association between early-life disease exposure and all-cause mortality risk after age 15 or 50. We also found no link between early-life disease exposure and probability of death specifically from cardiovascular disease, stroke, or cancer. Independent of survival, there was no evidence to support associations between early-life disease exposure and any of several aspects of reproductive performance, including lifetime reproductive success and age at first birth, in either males or females. Our results do not support the prevailing assertion that exposure to infectious diseases in early life has long-lasting associations with later-life all-cause mortality risk or mortality putatively linked to chronic inflammation. Variation in adulthood conditions could therefore be the most likely source of recent increases in adult life span.

The 'Developmental Origins' Hypothesis: relevance to the obstetrician and gynecologist

The recognition of 'fetal origins of adult disease' has placed new responsibilities on the obstetrician, as antenatal care is no longer simply about ensuring good perinatal outcomes, but also needs to plan for optimal long-term health for mother and baby. Recently, it has become clear that the intrauterine environment has a broad and long-lasting impact, influencing fetal and childhood growth and development as well as future cardiovascular health, non-communicable disease risk and fertility. This article looks specifically at the importance of the developmental origins of ovarian reserve and ageing, the role of the placenta and maternal nutrition before and during pregnancy. It also reviews recent insights in developmental medicine of relevance to the obstetrician, and outlines emerging evidence supporting a proactive clinical approach to optimizing periconceptional as well as antenatal care aimed to protect newborns against long-term disease susceptibility.

Body mass index, physical activity and fecundability in a North American preconception cohort study

OBJECTIVE

To evaluate the association between adiposity, physical activity (PA), and fecundability.

DESIGN

Prospective cohort study.

SETTING

Not applicable.

PATIENT(S)

A total of 2,062 female pregnancy planners from the United States and Canada who were enrolled during the preconception period.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Self-reported pregnancy. Fecundability ratios (FRs) and 95% confidence intervals (CIs) were estimated using proportional probabilities models that adjusted for potential confounders.

RESULT(S)

Relative to body mass index (BMI) 18.5-24 kg/m(2), FRs for BMI <18.5, 25-29, 30-34, 35-39, 40-44, and ≥45 kg/m(2) were 1.05 (95% CI 0.76-1.46), 1.01 (95% CI 0.89-1.15), 0.98 (95% CI 0.82-1.18), 0.78 (95% CI 0.60-1.02), 0.61 (95% CI 0.42-0.88), and 0.42 (95% CI 0.23-0.76), respectively. Reduced fecundability was observed among women with the largest waist-to-hip ratios (≥0.85 vs. <0.75; FR = 0.87, 95% CI 0.74-1.01) and waist circumferences (≥36 vs. <26 inches [≥90 vs. <66 cm]; FR = 0.80, 95% CI 0.59-1.01). Tendency to gain weight in the chest/shoulders (FR = 0.63, 95% CI 0.36-1.08) and waist/stomach (FR = 0.90, 95% CI 0.79-1.02), relative to hips/thighs, was associated with lower fecundability. Moderate PA was associated with increased fecundability (≥5 vs. <1 h/wk; FR = 1.26, 95% CI 0.96-1.65), but there was no dose-response relation. Among overweight/obese women (BMI ≥25 kg/m(2)), fecundability was 27% higher for vigorous PA of ≥5 versus <1 h/wk (95% CI 1.02-1.57).

CONCLUSION(S)

Various measures of overall and central adiposity were associated with decreased fertility among pregnancy planners. Vigorous PA was associated with improved fertility among overweight and obese women only; moderate PA was associated with improved fertility among all women.

Association of Fecundity With Changes in Adult Female Weight

OBJECTIVE

To evaluate whether weight change since age 18 years, current body mass index (BMI), and BMI at age 18 years are associated with fecundity.

METHODS

Our study included 1,950 women in the Nurses' Health Study 3 (2010-2014), a prospective cohort study, currently attempting pregnancy. Height, current weight, and weight at age 18 years were self-reported on the baseline questionnaire. Every 3-6 months thereafter, women reported the current duration of their pregnancy attempt. Multivariable-accelerated failure time models were used to estimate the time ratios and 95% confidence intervals (CIs).

RESULTS

For every 5-kg increase in body weight from age 18 years, current duration of pregnancy attempt increased by 5% (95% CI 3-7%). Compared with women who maintained weight, the adjusted median current duration was 0.5 months shorter in those who lost weight, 0.3 months longer for those who gained 4-9.9 kg and 10-19.9 kg, and 1.4 months longer for those who gained 20 kg or more (P trend ≤.001). The adjusted time ratio (95% CI) for a 5-kg/m increase in current BMI was 1.08 (1.04-1.12). After multivariable adjustment (including adjustment for current BMI), being underweight at age 18 years (BMI less than 18.5) was associated with a longer current duration of pregnancy attempt compared with normal-weight women (time ratio 1.25, 95% CI 1.07-1.47); however, being overweight or obese at age 18 years was not associated with fecundity.

CONCLUSION

Gaining weight in adulthood, being overweight or obese in adulthood, and being underweight at age 18 years were associated with a modest reduction in fecundity.

LEVEL OF EVIDENCE

II.

Are semen parameters related to birth weight?

Several experimental models suggest a link between maternal nutrition during gestation and reproductive function in offspring, but the impact of birth weight on male fertility in adulthood in humans is poorly documented. To study whether birth weight is associated with unexplained male subfertility later in life, we evaluated the relationship between birth weight and sperm parameters in adulthood in white subfertile men, partners of couples with primary idiopathic subfertility, and fertile men recruited within the ALIFERT (Diet and Its Relationship with Couple Infertility) study. Total sperm count, progressive motility, and sperm DNA fragmentation were analyzed in sperm, and metabolic assays were performed on blood. Birth weight was associated with sperm DNA fragmentation and inversely correlated with total sperm count, underlining the importance of the in utero environment for male reproductive function.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01093378.

A prospective cohort study of a woman's own gestational age and her fecundability

STUDY QUESTION

What is the magnitude of the association between a woman's gestational age at her own birth and her fecundability (cycle-specific probability of conception)?

SUMMARY ANSWER

We found a 62% decrease in fecundability among women born <34 weeks of gestation relative to women born at 37-41 weeks of gestation, whereas there were few differences in fecundability among women born at later gestational ages.

WHAT IS KNOWN ALREADY

One study, using retrospectively collected data on time-to-pregnancy (TTP), and self-reported data on gestational age, found a prolonged TTP among women born <37 gestational weeks (preterm) and with a birthweight ≤1500 g. Other studies of women's gestational age at birth and subsequent fertility, based on data from national birth registries, have reported a reduced probability of giving birth among women born <32 weeks of gestation.

STUDY DESIGN, SIZE, DURATION

We used data from a prospective cohort study of Danish pregnancy planners ('Snart-Gravid'), enrolled during 2007-2011 and followed until 2012. In all, 2814 women were enrolled in our study, of which 2569 had complete follow-up.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women eligible to participate were 18-40 years old at study entry, in a relationship with a male partner, and attempting to conceive. Participants completed a baseline questionnaire and up to six follow-up questionnaires until the report of pregnancy, discontinuation of pregnancy attempts, beginning of fertility treatment, loss to follow-up or end of study observation after 12 months.

MAIN RESULTS AND THE ROLE OF CHANCE

Among women born <34 gestational weeks, the cumulative probability of conception was 12, 28 and 48% within 3, 6 and 12 cycles, respectively. Among women born at 37-41 weeks of gestation, cumulative probability of conception was 47, 67 and 84% within 3, 6 and 12 cycles, respectively. Relative to women born at 37-41 weeks' gestation, women born <34 weeks had decreased fecundability (fecundability ratio (FR) 0.38, 95% confidence interval (CI): 0.17-0.82). Our data did not suggest reduced fecundability among women born at 34-36 weeks of gestation or at ≥42 weeks of gestation (FR 1.03, 95% CI: 0.80-1.34, and FR 1.13, 95% CI: 0.96-1.33, respectively).

LIMITATIONS, REASONS FOR CAUTION

Data on gestational age, obtained from the Danish Medical Birth Registry, were more likely to be based on date of last menstrual period than early ultrasound examination, possibly leading to an overestimation of gestational age at birth. Such overestimation, however, would not explain the decrease in fecundability observed among women born <34 gestational weeks. Another limitation is that the proportion of women born before 34 weeks of gestation was low in our study population, which reduced the precision of the estimates.

WIDER IMPLICATIONS OF THE FINDINGS

By using prospective data on TTP, our study elaborates on previous reports of impaired fertility among women born preterm, suggesting that women born <34 weeks of gestation have reduced fecundability.

STUDY FUNDING/COMPETING INTERESTS

The study was supported by the National Institute of Child Health and Human Development (R21-050264), the Danish Medical Research Council (271-07-0338), and the Health Research Fund of Central Denmark Region (1-01-72-84-10). The authors have no competing interests to declare.

Maternal undernutrition induces premature reproductive senescence in adult female rat offspring

OBJECTIVE

To determine the effects of maternal undernutrition (MUN) on the reproductive axis of aging offspring.

DESIGN

Animal (rat) study.

SETTING

Research laboratory.

ANIMAL(S)

Female Sprague-Dawley rats.

INTERVENTION(S)

Food restriction during the second half of pregnancy in rats.

MAIN OUTCOME MEASURE(S)

Circulating gonadotropins, antimüllerian hormone (AMH), ovarian morphology, estrous cyclicity, and gene expression studies in the hypothalamus and ovary in 1-day-old (P1) and aging adult offspring.

RESULT(S)

Offspring of MUN dams had low birth weight (LBW) and by adult age developed obesity. In addition, 80% of adult LBW offspring had disruption of estrous cycle by 8 months of age, with the majority of animals in persistent estrous. Ovarian morphology was consistent with acyclicity, with ovaries exhibiting large cystic structures and reduced corpora lutea. There was an elevation in circulating T, increased ovarian expression of enzymes involved in androgen synthesis, an increase in plasma LH/FSH levels, a reduction in E2 levels, and no changes in AMH in adult LBW offspring compared with in control offspring. Hypothalamic expression of leptin receptor (ObRb), estrogen receptor-α (ER-α), and GnRH protein was altered in an age-dependent manner with increased ObRb and ER-α expression in P1 LBW hypothalami and a reversal of this expression pattern in adult LBW hypothalami.

CONCLUSION(S)

Our data indicate that the maternal nutritional environment programs the reproductive potential of the offspring through alteration of the hypothalamic-pituitary-gonadal axis. The premature reproductive senescence in LBW offspring could be secondary to the development of obesity and hyperleptinemia in these animals in adult life.

Weight at birth and subsequent fecundability: a prospective cohort study

Objective

To examine the association between a woman's birth weight and her subsequent fecundability.

Method

In this prospective cohort study, we included 2,773 Danish pregnancy planners enrolled in the internet-based cohort study “Snart-Gravid”, conducted during 2007–2012. Participants were 18–40 years old at study entry, attempting to conceive, and were not receiving fertility treatment. Data on weight at birth were obtained from the Danish Medical Birth Registry and categorized as <2,500 grams, 2,500–2,999 grams, 3,000–3,999 grams, and ≥4,000 grams. In additional analyses, birth weight was categorized according to z-scores for each gestational week at birth. Time-to-pregnancy measured in cycles was used to compute fecundability ratios (FR) and 95% confidence intervals (CI), using a proportional probabilities regression model.

Results

Relative to women with a birth weight of 3,000–3,999 grams, FRs adjusted for gestational age, year of birth, and maternal socio-demographic and medical factors were 0.99 (95% CI: 0.73;1.34), 0.99 (95% CI: 0.87;1.12), and 1.08 (95% CI: 0.94;1.24) for birth weight <2,500 grams, 2,500–2,999 grams, and ≥4,000 grams, respectively. Estimates remained unchanged after further adjustment for markers of the participant's mother's fecundability. We obtained similar results when we restricted to women who were born at term, and to women who had attempted to conceive for a maximum of 6 cycles before study entry. Results remained similar when we estimated FRs according to z-scores of birth weight.

Conclusion

Our results indicate that birth weight appears not to be an important determinant of fecundability.

Body size and time-to-pregnancy in black women

STUDY QUESTION

Are overall and central obesity associated with reduced fecundability in US black women?

SUMMARY ANSWER

Overall and central obesity--based on self-reported measures of body mass index (BMI, kg/m(2)), waist circumference and waist-to-hip ratio--were independent risk factors for subfertility in our cohort.

WHAT IS KNOWN ALREADY

Overall obesity (BMI ≥ 30 kg/m(2)) has been associated with infertility in several studies. The role of central obesity is less clear. There are no previous studies of time-to-pregnancy (TTP) in black women.

STUDY DESIGN, SIZE, DURATION

Data were derived from the Black Women's Health Study, a prospective cohort study. During 1995-2011, there were 2239 planned pregnancy attempts reported by 1697 women, resulting in 2022 births. Cohort retention was greater than 80%.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Eligible women were aged 21-40 years and reported at least one planned pregnancy attempt during 1995-2011. Height and weight were reported in 1995, with weight updated every two years; waist and hip circumferences were reported in 1995 and updated in 2003. A validation study within the cohort showed high correlations between self-reported and technician-measured weight (r = 0.97), height (r = 0.93), waist circumference (r = 0.75) and hip circumference (r = 0.74). In 2011, TTP was reported in months. Proportional probabilities regression models were used to estimate fecundability ratios (FRs) and 95% confidence intervals (CI), adjusting for covariates.

MAIN RESULTS AND THE ROLE OF CHANCE

High BMI was associated with delayed conception: relative to BMI 18.5-24.9, FRs for BMI categories of <18.5, 25.0-29.9, 30.0-34.9 and ≥ 35.0 were 0.92 (CI: 0.64-1.32), 0.93 (CI: 0.84-1.03), 0.92 (CI: 0.79-1.06) and 0.73 (CI: 0.61-0.87), respectively. Associations were stronger among nulliparous women (P-interaction = 0.003). After controlling for BMI, reduced fecundability was observed among women with large waist circumferences (≥ 33 versus <26 inches: FR = 0.73, CI: 0.60-0.88) and large waist-to-hip ratios (≥ 0.85 versus <0.71: FR = 0.83, CI: 0.71-0.97).

LIMITATIONS, REASONS FOR CAUTION

TTP was reported retrospectively and error in recall is likely, particularly as time since the pregnancy increases. However, results were similar when based on the most recent versus first pregnancies. Confounding may have been introduced by the lack of control for important determinants of TTP. Nevertheless, control for maternal age and education, which are highly correlated with TTP determinants such as paternal age and persistence in trying, should reduce the extent of confounding. The analysis was confined to planned pregnancies. If pregnancy intention was related both to body size and fecundability, our results could be biased. Bias is likely to be small because we found little difference in body size and other measured characteristics between pregnancy planners and non-planners.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings add to the growing body of literature showing that excess BMI is associated with reduced fecundability and further suggest that central obesity is an important independent risk factor for infertility. The relation of obesity to infertility is especially relevant to US black women because they have higher rates of obesity and infertility. Reductions in overall and central obesity may offer the potential to improve fertility outcomes.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by National Cancer Institute grant CA58420. We have no competing interests to report.

Why do women have more children than they want? Understanding differences in women's ideal and actual family size in a natural fertility population

OBJECTIVES

We develop and test a conceptual model of factors influencing women's ideal family size (IFS) in a natural fertility population, the Tsimane of Bolivia. The model posits affects of socioecology, reproductive history, maternal condition, and men's IFS. We test three hypotheses for why women may exceed their IFS despite experiencing socioeconomic development: (H(1) ) limited autonomy; (H(2) ) improved maternal condition; and (H(3) ) low returns on investments in embodied capital.

METHODS

Women's reproductive histories and prospective fertility data were collected from 2002 to 2008 (n = 305 women). Semistructured interviews were conducted with Tsimane women to study the perceived value of parental investment (n = 76). Multiple regression, t-tests, and analysis of variance (ANOVA) are used to test model predictions.

RESULTS

Women's IFS is predicted by their socioecology, reproductive history, maternal condition, and husband's IFS. Hypotheses 2 and 3 are supported. Couples residing near town have smaller IFS (women = 3.75 ± 1.64; men = 3.87 ± 2.64) and less variance in IFS. However, the degree fertility exceeds IFS is inversely correlated with distance to town (Partial r = -0.189, df = 156, P = 0.018). Women living near town have greater maternal condition but 64% value traditional skills over formal schooling and 88% believe living in town is unfeasible.

CONCLUSIONS

While reduced IFS is evident with socioeconomic development, fertility decline may not immediately follow. When perceived benefits of investment in novel forms of embodied capital are low, and somatic wealth and large kin networks persist as important components of fitness, fertility may remain high and increase if maternal condition improves.

Twinning Rates According to Maternal Birthweight

Dizygotic twinning rates have changed over time, which has been seen as a sign of a decline in fecundity. Since a woman's birthweight has been shown to be a marker of her fecundity, maternal birthweight may correlate with subsequent twinning rates. In the Danish National Birth Cohort (1996–2002), we examined if maternal birthweight, and whether she was born at term or preterm, correlated with her probability of multiple birth. For 20,719 live born infants, we had self-reported information about maternal birthweight, collected during the first wave of the 7-year follow-up, and information on multiple births from record linkage. The association between maternal birthweight and multiple births was investigated by use of logistic regression and presented as odds ratios (ORs) with 95% confidence intervals (CIs). Compared to women born at term with a birthweight of 3001–4000 g, women with a birthweight > 4500 g appeared to have higher chance of multiple birth while women with a birthweight of 4001–4500 had a lower chance, especially if the analysis was restricted to women with a BMI < 25 (Adjusted ORs 2.3 [1.0–5.4] and 0.4 [0.2–0.9] respectively). Odds ratios for dizygotic twinning were of the same magnitude. In women with a BMI ≥ 25, no obvious pattern was present. Our findings do not indicate that twinning is a fecundity indicator. Women with a birthweight that may indicate a pregnancy complicated with gestational diabetes had the highest rate of multiple birth. These findings are new and should be put to a critical test in other data sources.

The impact of female obesity on the outcome of fertility treatment

The rising prevalence of obesity has had a profound impact on female reproductive health. Increased body mass index (BMI) is associated with ovulatory subfertility and anovulatory infertility. Overweight and obese women have poorer outcomes following fertility treatment. They respond poorly to clomiphene induction of ovulation and require higher doses of gonadotrophins for ovulation induction and superovulation. Ovarian stimulation for assisted reproduction produces fewer follicles resulting in the harvest of fewer oocytes. Fertilization rates are poorer and the embryo quality is impaired in younger women who are obese. Pregnancy rate in some studies is lower and there is an increased risk of early pregnancy loss. Weight loss regularizes menstrual cycles and increases the chance of spontaneous ovulation and conception in anovulatory overweight and obese women. Gradual sustained weight loss is beneficial whereas crash dieting is detrimental.

Endometrial gene expression in the window of implantation is altered in obese women especially in association with polycystic ovary syndrome

OBJECTIVE

To determine whether luteal phase endometrial transcriptome is altered in obese women during the window of implantation (WOI), considering the presence of infertility, fat distribution and association with polycystic ovary syndrome (PCOS).

DESIGN

Prospective study.

SETTING

University-affiliated infertility clinic, between May 2007 and March 2009.

PATIENT(S)

One control group of women with normal weight (n=4), and four study groups of obese women (n=6 each one) according to the association with infertility, PCOS, and ovarian stimulation.

INTERVENTION(S)

The endometrium was biopsied 7 days after LH surge or hCG administration in 28 women.

MAIN OUTCOME MEASURE(S)

Endometrial gene expression during the WOI.

RESULT(S)

One hundred and fifty-one genes were dysregulated in obese groups compared with controls. This dysregulation was more pronounced when infertility was associated. The biologic processes of these genes belonged mainly to development and regulation of different biological functions such as transcription and biosynthesis. The molecular functions overrepresented were transcription and peptide receptor activity. The endometrium of obese women with PCOS showed dysregulated genes related to biologic processes such as development, morphogenesis, and the immune system, as well as different molecular functions such as protein binding, binding, growth factor activity, and carboxylic acid transmembrane transporter activity. Some of these genes have been previously related to implantation and unexplained infertility.

CONCLUSION(S)

Obese women present a different endometrial gene expression than controls during the WOI, which is more pronounced when infertility or polycystic ovary syndrome are associated.

Food availability at birth limited reproductive success in historical humans

Environmental conditions in early life can profoundly affect individual development and have consequences for reproductive success. Limited food availability may be one of the reasons for this, but direct evidence linking variation in early-life nutrition to reproductive performance in adulthood in natural populations is sparse. We combined historical agricultural data with detailed demographic church records to investigate the effect of food availability around the time of birth on the reproductive success of 927 men and women born in 18th-century Finland. Our study population exhibits natural mortality and fertility rates typical of many preindustrial societies, and individuals experienced differing access to resources due to social stratification. We found that among both men and women born into landless families (i.e., with low access to resources), marital prospects, probability of reproduction, and offspring viability were all positively related to local crop yield during the birth year. Such effects were generally absent among those born into landowning families. Among landless individuals born when yields of the two main crops, rye and barley, were both below median, only 50% of adult males and 55% of adult females gained any reproductive success in their lifetime, whereas 97% and 95% of those born when both yields were above the median did so. Our results suggest that maternal investment in offspring in prenatal or early postnatal life may have profound implications for the evolutionary fitness of human offspring, particularly among those for which resources are more limiting. Our study adds support to the idea that early nutrition can limit reproductive success in natural animal populations, and provides the most direct evidence to date that this process applies to humans.

An internet-based prospective study of body size and time-to-pregnancy

BACKGROUND

Recent studies have shown that both female and male obesity may delay time-to-pregnancy (TTP). Little is known about central adiposity or weight gain and fecundability in women.

METHODS

We examined the association between anthropometric factors and TTP among 1651 Danish women participating in an internet-based prospective cohort study of pregnancy planners (2007-2008). We categorized body mass index (BMI = kg/m(2)) as underweight (<20), normal weight (20-24), overweight (25-29), obese (30-34) and very obese (> or =35). We used discrete-time Cox regression to estimate fecundability ratios (FRs) and 95% confidence intervals (CI), controlling for potential confounders.

RESULTS

We found longer TTPs for overweight (FR = 0.83, 95% CI = 0.70-1.00), obese (FR = 0.75, 95% CI = 0.58-0.97), and very obese (FR = 0.61, 95% CI = 0.42-0.88) women, compared with normal weight women. After further control for waist circumference, FRs for overweight, obese, and very obese women were 0.72 (95% CI = 0.58-0.90), 0.60 (95% CI = 0.42-0.85) and 0.48 (95% CI = 0.31-0.74), respectively. Underweight was associated with reduced fecundability among nulliparous women (FR = 0.82, 95% CI = 0.63-1.06) and increased fecundability among parous women (FR = 1.61, 95% CI = 1.08-2.39). Male BMI was not materially associated with TTP after control for female BMI. Compared with women who maintained a stable weight since age 17 (-5 to 4 kg), women who gained > or =15 kg had longer TTPs (FR = 0.72, 95% CI = 0.59-0.88) after adjustment for BMI at age 17. Associations of waist circumference and waist-to-hip ratio with TTP depended on adjustment for female BMI: null associations were observed before adjustment for BMI and weakly positive associations were observed after adjustment for BMI.

CONCLUSIONS

Our results confirm previous studies showing reduced fertility in overweight and obese women. The association between underweight and fecundability varied by parity.