Spontaneous abortion and preterm labor and delivery in nonhuman primates: evidence from a captive colony of chimpanzees (Pan troglodytes)

Background

Preterm birth is a leading cause of perinatal mortality, yet the evolutionary history of this obstetrical syndrome is largely unknown in nonhuman primate species.

Methodology/Principal Findings

We examined the length of gestation during pregnancies that occurred in a captive chimpanzee colony by inspecting veterinary and behavioral records spanning a total of thirty years. Upon examination of these records we were able to confidently estimate gestation length for 93 of the 97 (96%) pregnancies recorded at the colony. In total, 78 singleton gestations resulted in live birth, and from these pregnancies we estimated the mean gestation length of normal chimpanzee pregnancies to be 228 days, a finding consistent with other published reports. We also calculated that the range of gestation in normal chimpanzee pregnancies is approximately forty days. Of the remaining fifteen pregnancies, only one of the offspring survived, suggesting viability for chimpanzees requires a gestation of approximately 200 days. These fifteen pregnancies constitute spontaneous abortions and preterm deliveries, for which the upper gestational age limit was defined as 2 SD from the mean length of gestation (208 days).

Conclusions/Significance

The present study documents that preterm birth occurred within our study population of captive chimpanzees. As in humans, pregnancy loss is not uncommon in chimpanzees, In addition, our findings indicate that both humans and chimpanzees show a similar range of normal variation in gestation length, suggesting this was the case at the time of their last common ancestor (LCA). Nevertheless, our data suggest that whereas chimpanzees'' normal gestation length is ∼20–30 days after reaching viability, humans'' normal gestation length is approximately 50 days beyond the estimated date of viability without medical intervention. Future research using a comparative evolutionary framework should help to clarify the extent to which mechanisms at work in normal and preterm parturition are shared in these species.     

Contribution of Risk Factors to Extremely,Very and Moderately Preterm Births – Register-Based Analysis of 1,390,742 Singleton Births

Background

Preterm birth, defined as birth occurring before 37 weeks gestation, is one of the most significant contributors to neonatal mortality and morbidity, with long-term adverse consequences for health, and cognitive outcome.

Objective

The aim of the present study was to identify risk factors of preterm birth (≤36+6 weeks gestation) among singleton births and to quantify the contribution of risk factors to socioeconomic disparities in preterm birth.

Methods

A retrospective population–based case-control study using data derived from the Finnish Medical Birth Register. A total population of singleton births in Finland from 1987−2010 (n = 1,390,742) was reviewed.

Results

Among all singleton births (n = 1,390,742), 4.6% (n = 63,340) were preterm (<37 weeks), of which 0.3% (n = 4,452) were classed as extremely preterm, 0.4% (n = 6,213) very preterm and 3.8% (n = 54,177) moderately preterm. Smoking alone explained up to 33% of the variation in extremely, very and moderately preterm birth incidence between high and the low socioeconomic status (SES) groups. Reproductive risk factors (placental abruption, placenta previa, major congenital anomaly, amniocentesis, chorionic villus biopsy, anemia, stillbirth, small for gestational age (SGA) and fetal sex) altogether explained 7.7−25.0% of the variation in preterm birth between SES groups.

Conclusions

Smoking explained about one third of the variation in preterm birth groups between SES groups whereas the contribution of reproductive risk factors including placental abruption, placenta previa, major congenital anomaly, amniocentesis, chorionic villus biopsy, anemia, stillbirth, SGA and fetal sex was up to one fourth.     

Antenatal Maternal Emotional Distress and Duration of Pregnancy

Objective(s)

We sought to prospectively study the association between antenatal emotional distress and gestational length at birth as well as preterm birth.

Study Design

We followed up 40,077 primiparous women in the Norwegian Mother and Child Cohort Study. Emotional distress was reported in a short form of the Hopkins Symptom Checklist-25 (SCL-5) at 17 and 30 weeks of gestation. Gestational length at birth, obtained from the Medical Birth Registry of Norway, was used as continuous (gestational length in days) and categorized (early preterm (22–31 weeks) and late preterm (32–36 weeks) versus term birth (≥37 weeks)) outcome, using linear and logistic regression analysis, respectively. Births were divided into spontaneous and provider-initiated.

Results

Of all women, 7.4% reported emotional distress at 17 weeks, 6.0% at 30 weeks and 5.1% had a preterm birth. All measurements of emotional distress at 30 weeks were significantly associated with a reduction of gestational length, in days, for provider-initiated births at term. Emotional distress at 30 weeks showed a reduced duration of pregnancy at birth of 2.40 days for provider-initiated births at term. An increase in emotional distress from 17 to 30 weeks was associated with a reduction of gestational length at birth of 2.13 days for provider-initiated births at term. Sustained high emotional distress was associated with a reduction of gestational length at birth of 2.82 days for provider-initiated births. Emotional distress did not increase the risk of either early or late preterm birth.

Conclusion

Emotional distress at 30 weeks, an increase in emotional distress from 17 to 30 weeks and sustained high levels of emotional distress were associated with a reduction in gestational length in days for provider-initiated term birth. We found no significant association between emotional distress and the risk of preterm birth.     

Time Course Study of Blood Pressure in Term and Preterm Infants Immediately after Birth

Objective

To describe temporal changes in systolic, diastolic, and mean blood pressure (SBP, DBP, and MBP, respectively) in term and preterm infants immediately after birth.

Methods

Prospective observational two-center study. In term infants SBP, DBP, and MBP were assessed non-invasively every minute for the first 15 minutes, and in preterm infants every minute for the first 15 minutes, as well as at 20, 25, 30, 45, and 60 minutes after birth. Regression analyses were performed by gender and respiratory support in all neonates; and by mode of delivery, cord clamping time, and development of ultrasound-detected brain injury in preterm neonates.

Results

Term infants (n = 54) had a mean (SD) birth weight of 3298 (442) g and gestational age of 38 (1) weeks, and preterm infants (n = 94) weighed 1340 (672) g and were 30 (3) weeks gestation. Term infants’ SBP, DBP and MBP within the first 15 minutes after birth were independent of gender or respiratory support. Linear mixed regression analysis showed that preterm infants, who were female, born vaginally, had delayed cord clamping and did not require positive pressure ventilation nor develop periventricular injury or ventriculomegaly, had significantly higher SBP, DBP, and MBP at some measurement points within the first hour after birth.

Conclusions

We present novel reference ranges of BP immediately after birth in a cohort of term and preterm neonates. They may aid in optimization of cardiovascular support during early transition at all gestations.     

Refractive Status at Birth: Its Relation to Newborn Physical Parameters at Birth and Gestational Age

Background

Refractive status at birth is related to gestational age. Preterm babies have myopia which decreases as gestational age increases and term babies are known to be hypermetropic. This study looked at the correlation of refractive status with birth weight in term and preterm babies, and with physical indicators of intra-uterine growth such as the head circumference and length of the baby at birth.

Methods

All babies delivered at St. Stephens Hospital and admitted in the nursery were eligible for the study. Refraction was performed within the first week of life. 0.8% tropicamide with 0.5% phenylephrine was used to achieve cycloplegia and paralysis of accommodation. 599 newborn babies participated in the study. Data pertaining to the right eye is utilized for all the analyses except that for anisometropia where the two eyes were compared. Growth parameters were measured soon after birth. Simple linear regression analysis was performed to see the association of refractive status, (mean spherical equivalent (MSE), astigmatism and anisometropia) with each of the study variables, namely gestation, length, weight and head circumference. Subsequently, multiple linear regression was carried out to identify the independent predictors for each of the outcome parameters.

Results

Simple linear regression showed a significant relation between all 4 study variables and refractive error but in multiple regression only gestational age and weight were related to refractive error. The partial correlation of weight with MSE adjusted for gestation was 0.28 and that of gestation with MSE adjusted for weight was 0.10. Birth weight had a higher correlation to MSE than gestational age.

Conclusion

This is the first study to look at refractive error against all these growth parameters, in preterm and term babies at birth. It would appear from this study that birth weight rather than gestation should be used as criteria for screening for refractive error, especially in developing countries where the incidence of intrauterine malnutrition is higher.     

Cervical Mucus Properties Stratify Risk for Preterm Birth

Background

Ascending infection from the colonized vagina to the normally sterile intrauterine cavity is a well-documented cause of preterm birth. The primary physical barrier to microbial ascension is the cervical canal, which is filled with a dense and protective mucus plug. Despite its central role in separating the vaginal from the intrauterine tract, the barrier properties of cervical mucus have not been studied in preterm birth.

Methods and Findings

To study the protective function of the cervical mucus in preterm birth we performed a pilot case-control study to measure the viscoelasticity and permeability properties of mucus obtained from pregnant women at high-risk and low-risk for preterm birth. Using extensional and shear rheology we found that cervical mucus from women at high-risk for preterm birth was more extensible and forms significantly weaker gels compared to cervical mucus from women at low-risk of preterm birth. Moreover, permeability measurements using fluorescent microbeads show that high-risk mucus was more permeable compared with low-risk mucus.

Conclusions

Our findings suggest that critical biophysical barrier properties of cervical mucus in women at high-risk for preterm birth are compromised compared to women with healthy pregnancy. We hypothesize that impaired barrier properties of cervical mucus could contribute to increased rates of intrauterine infection seen in women with preterm birth. We furthermore suggest that a robust association of spinnbarkeit and preterm birth could be an effectively exploited biomarker for preterm birth prediction.     

Loss of cannabinoid receptor CB1 induces preterm birth

Background

Preterm birth accounting approximate 10% of pregnancies in women is a tremendous social, clinical and economic burden. However, its underlying causes remain largely unknown. Emerging evidence suggests that endocannabinoid signaling via cannabinoid receptor CB1 play critical roles in multiple early pregnancy events in both animals and humans. Since our previous studies demonstrated that loss of CB1 defers the normal implantation window in mice, we surmised that CB1 deficiency would influence parturition events.

Methods and Findings

Exploiting mouse models with targeted deletion of Cnr1, Cnr2 and Ptgs1 encoding CB1, CB2 and cyclooxygenase-1, respectively, we examined consequences of CB1 or CB2 silencing on the onset of parturition. We observed that genetic or pharmacological inactivation of CB1, but not CB2, induced preterm labor in mice. Radioimmunoassay analysis of circulating levels of ovarian steroid hormones revealed that premature birth resulting from CB1 inactivation is correlated with altered progesterone/estrogen ratios prior to parturition. More strikingly, the phenotypic defects of prolonged pregnancy length and parturition failure in mice missing Ptgs1 were corrected by introducing CB1 deficiency into Ptgs1 null mice. In addition, loss of CB1 resulted in aberrant secretions of corticotrophin-releasing hormone and corticosterone during late gestation. The pathophysiological significance of this altered corticotrophin-releasing hormone-driven endocrine activity in the absence of CB1 was evident from our subsequent findings that a selective corticotrophin-releasing hormone antagonist was able to restore the normal parturition timing in Cnr1 deficient mice. In contrast, wild-type females receiving excessive levels of corticosterone induced preterm birth.

Conclusions

CB1 deficiency altering normal progesterone and estrogen levels induces preterm birth in mice. This defect is independent of prostaglandins produced by cyclooxygenase-1. Moreover, CB1 inactivation resulted in aberrant corticotrophin-releasing hormone and corticosterone activities prior to parturition, suggesting that CB1 regulates labor by interacting with the corticotrophin-releasing hormone-driven endocrine axis.     

Lower versus Higher Oxygen Concentration for Delivery Room Stabilisation of Preterm Neonates: Systematic Review

Background

Emerging evidence suggests that initiating delivery room respiratory support or resuscitation for term infants using lower rather than higher concentrations of oxygen reduces mortality and the risk of serious morbidity. Uncertainty exists with regard to applicability of this strategy for preterm infants who have different underlying reasons for respiratory distress and risks for harm at birth than term infants.

Methods

We performed a systematic review and meta-analysis of randomised controlled trials to determine the effect on mortality and morbidity of using lower (21– 50%) versus higher (>50%) oxygen concentrations for delivery room transition support of preterm infants.

Results

We identified six randomised controlled trials in which a total of 484 infants participated. Most participants were preterm infants born before 32 weeks’ gestation. One trial was quasi-randomised and in one trial allocation concealment was not described. Clinicians and investigators were aware of the interventions in all but one trial. Meta-analyses found a statistically significant reduction in the risk of death pooled risk ratio 0.65 (95% confidence interval 0.43, 0.98), but this effect disappeared when only the four trials with adequate allocation concealment were included [pooled risk ratio 1.0 (95% confidence interval 0.45, 2.24)]. None of the trials has evaluated any neuro-developmental outcomes.

Conclusions

The available trial data do not provide strong evidence that using lower versus higher oxygen concentrations for delivery room transition support for preterm infants confers important benefits or harms. Lack of allocation concealment and blinding of clinicians and assessors are the major sources of bias in the existing trials. Further, large, good-quality trials are needed to resolve on-going uncertainties and inform clinical practice.     

Expression of Stretch-Activated Two-Pore Potassium Channels in Human Myometrium in Pregnancy and Labor

Background

We tested the hypothesis that the stretch-activated, four-transmembrane domain, two pore potassium channels (K2P), TREK-1 and TRAAK are gestationally-regulated in human myometrium and contribute to uterine relaxation during pregnancy until labor.

Methodology

We determined the gene and protein expression of K2P channels in non-pregnant, pregnant term and preterm laboring myometrium. We employed both molecular biological and functional studies of K2P channels in myometrial samples taken from women undergoing cesarean delivery of a fetus.

Principal Findings

TREK-1, but not TREK-2, channels are expressed in human myometrium and significantly up-regulated during pregnancy. Down-regulation of TREK-1 message was seen by Q-PCR in laboring tissues consistent with a role for TREK-1 in maintaining uterine quiescence prior to labor. The TRAAK channel was unregulated in the same women. Blockade of stretch-activated channels with a channel non-specific tarantula toxin (GsMTx-4) or the more specific TREK-1 antagonist L-methionine ethyl ester altered contractile frequency in a dose-dependent manner in pregnant myometrium. Arachidonic acid treatment lowered contractile tension an effect blocked by fluphenazine. Functional studies are consistent with a role for TREK-1 in uterine quiescence.

Conclusions

We provide evidence supporting a role for TREK-1 in contributing to uterine quiescence during gestation and hypothesize that dysregulation of this mechanism may underlie certain cases of spontaneous pre-term birth.     

Acute Histologic Chorioamnionitis Is a Risk Factor for Adverse Neonatal Outcome in Late Preterm Birth after Preterm Premature Rupture of Membranes

Background

The objective of this study was to determine whether acute histologic chorioamnionitis is associated with adverse neonatal outcomes in late preterm infants who were born after preterm PROM.

Methodology/Principal Findings

The relationship between the presence of acute histologic chorioamnionitis and adverse neonatal outcome was examined in patients with preterm PROM who delivered singleton preterm newborns between 34 weeks and 36 6/7 weeks of gestation. Nonparametric statistics were used for data analysis. The frequency of acute histologic chorioamnionitis was 24% in patients with preterm PROM who delivered preterm newborns between 34 weeks and 36 6/7 weeks of gestation. Newborns born to mothers with histologic chorioamnionitis had significantly higher rates of adverse neonatal outcome (74% vs 51%; p<0.005) than those without histologic chorioamnionitis. This relationship remained significant after adjustment for gestational age at preterm PROM, gestational age at delivery, and exposure to antenatal corticosteroids.

Conclusions/Significance

The presence of acute histologic chorioamnionitis is associated with adverse neonatal outcome in late preterm infants born to mothers with preterm PROM.     

Maternal Prenatal Positive Affect,Depressive and Anxiety Symptoms and Birth Outcomes: The PREDO Study

Background

We investigated whether maternal prenatal emotions are associated with gestational length and birth weight in the large PREDO Study with multiple measurement points of emotions during gestation.

Methods

Altogether 3376 pregnant women self-assessed their positive affect (PA, Positive and Negative Affect Schedule) and depressive (Center for Epidemiologic Studies Depression Scale, CES-D) and anxiety (Spielberger State Anxiety Scale, STAI) symptoms up to 14 times during gestation. Birth characteristics were derived from the National Birth Register and from medical records.

Results

One standard deviation (SD) unit higher PA during the third pregnancy trimester was associated with a 0.05 SD unit longer gestational length, whereas one SD unit higher CES-D and STAI scores during the third trimester were associated with 0.04–0.05 SD unit shorter gestational lengths (P-values ≤ 0.02), corresponding to only 0.1–0.2% of the variation in gestational length. Higher PA during the third trimester was associated with a significantly decreased risk for preterm (< 37 weeks) delivery (for each SD unit higher positive affect, odds ratio was 0.8-fold (P = 0.02). Mothers with preterm delivery showed a decline in PA and an increase in CES-D and STAI during eight weeks prior to delivery. Post-term birth (≥ 42 weeks), birth weight and fetal growth were not associated with maternal prenatal emotions.

Conclusions

This study with 14 measurements of maternal emotions during pregnancy show modest effects of prenatal emotions during the third pregnancy trimester, particularly in the weeks close to delivery, on gestational length. From the clinical perspective, the effects were negligible. No associations were detected between prenatal emotions and birth weight.     

Disentangling the Effects of Risk Factors and Clinical Care on Subnational Variation in Early Neonatal Mortality in the United States

Objective

Between 1990 and 2010, the U.S ranking in neonatal mortality slipped from 29^th to 45^th among countries globally. Substantial subnational variation in newborn mortality also exists. Our objective is to measure the extent to which trends and subnational variation in early neonatal mortality reflect differences in the prevalence of risk factors (gestational age and birth weight) compared to differences in clinical care.

Methods

Observational study using linked birth and death data for all births in the United States between 1996 and 2006. We examined health service area (HSA) level variation in the expected early neonatal mortality rate, based on gestational age (GA) and birth-weight (BW), and GA-BW adjusted mortality as a proxy for clinical care. We analyzed the relationship between selected health system indicators and GA-BW-adjusted mortality.

Results

The early neonatal death (ENND) rate declined 12% between 1996 and 2006 (2.39 to 2.10 per 1000 live births). This occurred despite increases in risk factor prevalence. There was significant HSA-level variation in the expected ENND rate (Rate Ratio: 0.73–1.47) and the GA-BW adjusted rate (Rate ratio: 0.63–1.68). Accounting for preterm volume (defined as <34 weeks), the number of neonatologist and NICU beds, 25.2% and 58.7% of the HSA-level variance in outcomes was explained among all births and very low birth weight babies, respectively.

Conclusion

Improvements in mortality could be realized through the expansion or reallocation of clinical neonatal resources, particularly in HSAs with a high volume of preterm births; however, prevention of preterm births and low-birth weight babies has a greater potential to improve newborn survival in the United States.     

White matter and cognition in adults who were born preterm

Background and Purpose

Individuals born very preterm (before 33 weeks of gestation, VPT) are at risk of damage to developing white matter, which may affect later cognition and behaviour.

Methods

We used diffusion tensor MRI (DT-MRI) to assess white matter microstructure (fractional anisotropy; FA) in 80 VPT and 41 term-born individuals (mean age 19.1 years, range 17–22, and 18.5 years, range17–22 years, respectively). VPT individuals were part of a 1982–1984 birth cohort which had been followed up since birth; term individuals were recruited by local press advertisement. General intellectual function, executive function and memory were assessed.

Results

The VPT group had reduced FA in four clusters, and increased FA in four clusters relative to the Term group, involving several association tracts of both hemispheres. Clusters of increased FA were associated with more severe neonatal brain injury in the VPT group. Clusters of reduced FA were associated with lower birth weight and perinatal hypoxia, and with reduced adult cognitive performance in the VPT group only.

Conclusions

Alterations of white matter microstructure persist into adulthood in VPT individuals and are associated with cognitive function.     

Risk factors for preterm birth in an international prospective cohort of nulliparous women

Objectives

To identify risk factors for spontaneous preterm birth (birth <37 weeks gestation) with intact membranes (SPTB-IM) and SPTB after prelabour rupture of the membranes (SPTB-PPROM) for nulliparous pregnant women.

Design

Prospective international multicentre cohort.

Participants

3234 healthy nulliparous women with a singleton pregnancy, follow up was complete in 3184 of participants (98.5%).

Results

Of the 3184 women, 156 (4.9%) had their pregnancy complicated by SPTB; 96 (3.0%) and 60 (1.9%) in the SPTB-IM and SPTB-PPROM categories, respectively. Independent risk factors for SPTB-IM were shorter cervical length, abnormal uterine Doppler flow, use of marijuana pre-pregnancy, lack of overall feeling of well being, being of Caucasian ethnicity, having a mother with diabetes and/or a history of preeclampsia, and a family history of low birth weight babies. Independent risk factors for SPTB-PPROM were shorter cervical length, short stature, participant’s not being the first born in the family, longer time to conceive, not waking up at night, hormonal fertility treatment (excluding clomiphene), mild hypertension, family history of recurrent gestational diabetes, and maternal family history of any miscarriage (risk reduction). Low BMI (<20) nearly doubled the risk for SPTB-PPROM (odds ratio 2.64; 95% CI 1.07–6.51). The area under the receiver operating characteristics curve (AUC), after internal validation, was 0.69 for SPTB-IM and 0.79 for SPTB-PPROM.

Conclusion

The ability to predict PTB in healthy nulliparous women using clinical characteristics is modest. The dissimilarity of risk factors for SPTB-IM compared with SPTB-PPROM indicates different pathophysiological pathways underlie these distinct phenotypes.

Trial Registration

ACTR.org.au ACTRN12607000551493     

Birth Weight Reference Percentiles for Chinese

Objective

To develop a reference of population-based gestational age-specific birth weight percentiles for contemporary Chinese.

Methods

Birth weight data was collected by the China National Population-based Birth Defects Surveillance System. A total of 1,105,214 live singleton births aged ≥28 weeks of gestation without birth defects during 2006–2010 were included. The lambda-mu-sigma method was utilized to generate percentiles and curves.

Results

Gestational age-specific birth weight percentiles for male and female infants were constructed separately. Significant differences were observed between the current reference and other references developed for Chinese or non-Chinese infants.

Conclusion

There have been moderate increases in birth weight percentiles for Chinese infants of both sexes and most gestational ages since 1980s, suggesting the importance of utilizing an updated national reference for both clinical and research purposes.     

The Effect of Changing Patterns of Obstetric Care in Scotland (1980–2004) on Rates of Preterm Birth and Its Neonatal Consequences: Perinatal Database Study

Background

Rates of preterm birth are rising worldwide. Studies from the United States and Latin America suggest that much of this rise relates to increased rates of medically indicated preterm birth. In contrast, European and Australian data suggest that increases in spontaneous preterm labour also play a role. We aimed, in a population-based database of 5 million people, to determine the temporal trends and obstetric antecedents of singleton preterm birth and its associated neonatal mortality and morbidity for the period 1980–2004.

Methods and Findings

There were 1.49 million births in Scotland over the study period, of which 5.8% were preterm. We found a percentage increase in crude rates of both spontaneous preterm birth per 1,000 singleton births (10.7%, p<0.01) and medically indicated preterm births (41.2%, p<0.01), which persisted when adjusted for maternal age at delivery. The greater proportion of spontaneous preterm births meant that the absolute increase in rates of preterm birth in each category were similar. Of specific maternal complications, essential and pregnancy-induced hypertension, pre-eclampsia, and placenta praevia played a decreasing role in preterm birth over the study period, with gestational and pre-existing diabetes playing an increasing role. There was a decline in stillbirth, neonatal, and extended perinatal mortality associated with preterm birth at all gestation over the study period but an increase in the rate of prolonged hospital stay for the neonate. Neonatal mortality improved in all subgroups, regardless of obstetric antecedent of preterm birth or gestational age. In the 28 wk and greater gestational groups we found a reduction in stillbirths and extended perinatal mortality for medically induced but not spontaneous preterm births (in the absence of maternal complications) although at the expense of a longer stay in neonatal intensive care. This improvement in stillbirth and neonatal mortality supports the decision making behind the 34% increase in elective/induced preterm birth in these women. Although improvements in neonatal outcomes overall are welcome, preterm birth still accounts for over 66% of singleton stillbirths, 65% of singleton neonatal deaths, and 67% of infants whose stay in the neonatal unit is “prolonged,” suggesting this condition remains a significant contributor to perinatal mortality and morbidity.

Conclusions

In our population, increases in spontaneous and medically induced preterm births have made equal contributions to the rising rate of preterm birth. Despite improvements in related perinatal mortality, preterm birth remains a major obstetric and neonatal problem, and its frequency is increasing. Please see later in the article for the Editors'' Summary     

The Impact of the Wenchuan Earthquake on Birth Outcomes

Background

Earthquakes and other catastrophic events frequently occurring worldwide can be considered as outliers and cause a growing and urgent need to improve our understanding of the negative effects imposed by such disasters. Earthquakes can intensively impact the birth outcomes upon psychological and morphological development of the unborn children, albeit detailed characteristics remain obscure.

Methods and Findings

We utilized the birth records at Du Jiang Yan and Peng Zhou counties to investigate the birth outcomes as a consequence of a major earthquake occurred in Wenchuan, China on May 12, 2008. Totally 13,003 of neonates were recorded, with 6638 and 6365 for pre- and post- earthquake, respectively. Significant low birthweight, high ratio of low birthweight, and low Apgar scores of post-earthquake group were observed. In contrast, the sex ratio at birth, birth length and length of gestation did not show statistical differences. The overall ratio of birth-defect in the post-earthquake (1.18%) is statistically high than that of pre-earthquake (0.99%), especially for those in the first trimester on earthquake day (1.47%). The birth-defect spectrum was dramatically altered after earthquake, with the markedly increased occurrences of ear malformations. The ratio of preterm birth post-earthquake (7.41%) is significant increased than that of pre-earthquake (5.63%). For the birth outcomes of twins, significant differences of the ratio of twins, birth weight, ratio of low birthweight and birth-defect rate were observed after earthquake.

Conclusion

A hospital-based study of birth outcomes impacted by the Wenchuan earthquake shows that the earthquake was associated with significant effects on birth outcomes, indicating it is a major monitor for long-term pregnant outcomes.     

Characterization of Dietary Patterns in the Danish National Birth Cohort in Relation to Preterm Birth

Background

Dietary patterns better reflect eating habits as opposed to single dietary components. However, the use of dietary pattern analysis in nutritional epidemiology has been hampered by the complexity of interpreting and presenting multidimensional dietary data.

Methods

This study extracts and visualizes dietary patterns from self-reported dietary data collected in mid-pregnancy (25^th week of gestation) from nearly 60,000 mother-child pairs part of a prospective, longitudinal cohort (Danish National Birth Cohort) and further examines their associations with spontaneous and induced preterm birth (gestational age<259 days (<37 weeks)).

Results

A total of seven dietary patterns were extracted by principal component analysis, characterized and visualized by color-coded spider plots, and referred to as: Vegetables/Prudent, Alcohol, Western, Nordic, Seafood, Candy and Rice/Pasta/Poultry. A consistent dose-response association with preterm birth was only observed for Western diet with an odds ratio of 1.30 (95% CI: 1.13, 1.49) comparing the highest to the lowest quintile. This association was primarily driven by induced preterm deliveries (odds ratio = 1.66, 95% CI: 1.30, 2.11, comparing the highest to the lowest quintile) while the corresponding odds ratio for spontaneous preterm deliveries was more modest (odds ratio = 1.18, 95% CI: 0.99, 1.39). All based on adjusted analyses.

Conclusions

In conclusion, this study presented a simple and novel framework for visualizing correlation structures between overall consumption of foods group and their relation to nutrient intake and maternal characteristics. Our results suggest that Western-type diet, high in meat and fats and low in fruits and vegetables, is associated with increased odds of induced preterm birth.