The associations of birth intervals with small-for-gestational-age,preterm, and neonatal and infant mortality: a meta-analysis

Background

Short and long birth intervals have previously been linked to adverse neonatal outcomes. However, much of the existing literature uses cross-sectional studies, from which deriving causal inference is complex. We examine the association between short/long birth intervals and adverse neonatal outcomes by calculating and meta-analyzing associations using original data from cohort studies conducted in low-and middle-income countries (LMIC).

Methods

We identified five cohort studies. Adjusted odds ratios (aOR) were calculated for each study, with birth interval as the exposure and small-for-gestational-age (SGA) and/or preterm birth, and neonatal and infant mortality as outcomes. The associations were controlled for potential confounders and meta-analyzed.

Results

Birth interval of shorter than 18 months had statistically significant increased odds of SGA (pooled aOR: 1.51, 95% CI: 1.31-1.75), preterm (pooled aOR: 1.58, 95% CI: 1.19-2.10) and infant mortality (pooled aOR: 1.83, 95% CI: 1.19-2.81) after controlling for potential confounding factors (reference 36-<60 months). It was also significantly associated with term-SGA, preterm-appropriate-for-gestational-age, and preterm-SGA. Birth interval over 60 months had increased risk of SGA (pooled aOR: 1.22, 95% CI: 1.07-1.39) and term-SGA (pooled aOR: 1.14, 95% CI: 1.03-1.27), but was not associated with other outcomes.

Conclusions

Birth intervals shorter than 18 months are significantly associated with SGA, preterm birth and death in the first year of life. Lack of access to family planning interventions thus contributes to the burden of adverse birth outcomes and infant mortality in LMICs. Programs and policies must assess ways to provide equitable access to reproductive health interventions to mothers before or soon after delivering a child, but also address underlying socioeconomic factors that may modify and worsen the effect of short intervals.

     

Effect of Modifiable Risk Factors on Preterm Birth: A Population Based-Cohort

Objectives The purpose of this study is to evaluate the prevalence, impact, and interaction of short interpregnancy interval (IPI), pre-pregnancy body mass index (BMI) category, and pregnancy weight gain (PWG) on the rate of preterm birth. Methods This is a population-based retrospective cohort study using vital statistics birth records from 2006 to 2011 in OH, US, analyzing singleton live births to multiparous mothers with recorded IPI (n?=?393,441). Preterm birth rate at <37 weeks gestational age was compared between the referent pregnancy (defined as normal pre-pregnancy maternal BMI, IPI of 12–24 months, and Institute of Medicine (IOM) recommended PWG) and those with short or long IPI, abnormal BMI (underweight, overweight, and obese), and high or low PWG (under or exceeding IOM recommendations). Results Only 6?% of the women in this study had a referent pregnancy, with a preterm birth rate of 7.6?% for this group. Short IPIs of <6 and 6–12 months were associated with increased rates of preterm birth rate to 12.9 and 10.4?%, respectively. Low PWG compared to IOM recommendations for pre-pregnancy BMI class was also associated with increased preterm birth rate of 13.2?% for all BMI classes combined. However, the highest rate of preterm birth of 25.2?% occurred in underweight women with short IPI and inadequate weight gain with _adjOR 3.44 (95?% CI 2.80, 4.23). The fraction of preterm births observed in this cohort that can be attributed to short IPIs is 5.9?%, long IPIs is 8.3?%, inadequate PWG is 7.5?%, and low pre-pregnancy BMI is 2.2?%. Conclusions Our analysis indicates that a significant proportion of preterm births in Ohio are associated with potentially modifiable risk factors. These data suggest public health initiatives focused on preterm birth prevention could include counseling and interventions to optimize preconception health and prenatal nutrition.     

Short interpregnancy interval and adverse birth outcomes in women of advanced age: a population-based study

Purpose

Short interpregnancy interval (IPI) has been linked with adverse birth outcomes. However, the association in advanced age women needs further investigation. This study aims to examine the association between short IPI and adverse birth outcomes including preterm birth, post-term birth, low birth weight, and macrosomia, in a population of advanced age U.S. women.

<Emphasis Type="Italic">Chlamydia trachomatis</Emphasis> and Adverse Pregnancy Outcomes: Meta-analysis of Patients With and Without Infection

Objectives

We conducted a meta-analysis to determine the association between Chlamydia trachomatis and adverse perinatal outcomes.

Methods

Electronic databases were searched between 1970 and 2013. Included studies reported perinatal outcomes in women with and without chlamydia. Summary odds ratios were calculated using fixed- and random-effects models. Study bias was assessed using a Funnel Plot and Begg’s test.

Results

Of 129 articles identified, 56 studies met the inclusion criteria encompassing 614,892 subjects. Chlamydia infection in pregnancy was associated with preterm birth (OR?=?1.27, 95% CI 1.05, 1.54) with a large quantity of heterogeneity (I²?=?61%). This association lost significance when limiting the analysis to high-quality studies based on the Newcastle–Ottawa Scale. Chlamydia infection in pregnancy was also associated with preterm premature rupture of membranes (OR?=?1.81, 95% CI 1.0, 3.29), endometritis (OR 1.69, 95% CI 1.20, 2.38), low birthweight (OR 1.34, 95% CI 1.21, 1.48), small for gestational age (OR 1.14, 95% CI 1.05, 1.25) and intrauterine fetal demise (OR 1.44, 95% CI 1.06, 1.94).

Conclusions

This review provides evidence that chlamydia in pregnancy is associated with a small increase in the odds of multiple adverse pregnancy outcomes. The literature is complicated by heterogeneity and the fact that the association may not hold in higher quality and prospective studies or those that use more contemporary nucleic acid testing.

     

Drinking-Water Herbicide Exposure in Indiana and Prevalence of Small-for-Gestational-Age and Preterm Delivery

Background

Atrazine and other corn herbicides are routinely detected in drinking water. Two studies on potential association of atrazine with small-for-gestational-age (SGA) and preterm birth prevalence found inconsistent results. Moreover, these studies did not control for individual-level potential confounders.

Objectives

Our retrospective cohort study evaluated whether atrazine in drinking water is associated with increased prevalence of SGA and preterm birth.

Methods

We developed atrazine concentration time series for 19 water systems in Indiana from 1993 to 2007 and selected all births (n = 24,154) based on geocoded mother’s residences. Log-binomial models were used to estimate prevalence ratios (PRs) for SGA and preterm delivery in relation to atrazine concentrations during various periods of the pregnancy. Models controlled for maternal demographic characteristics, prenatal care and reproductive history, and behavioral risk factors (smoking, drinking, drug use).

Results

Atrazine in drinking water during the third trimester and the entire pregnancy was associated with a significant increase in the prevalence of SGA. Atrazine in drinking water > 0.1 μg/L during the third trimester resulted in a 17–19% increase in the prevalence of SGA compared with the control group (< 0.1 μg/L). Mean atrazine concentrations over the entire pregnancy > 0.644 μg/L were associated with higher SGA prevalence than in the control group (adjusted PR = 1.14; 95% confidence interval, 1.03–1.24). No significant association was found for preterm delivery.

Conclusions

We found that atrazine, and perhaps other co-occurring herbicides in drinking water, is associated with an increased prevalence of SGA, but not preterm delivery.     

Is conception delay a risk factor for reduced gestation or birthweight?

Previous studies have suggested an association between delays in conception and adverse perinatal outcomes, specifically, low birthweight and preterm birth. We investigated the relationship between conception delay (defined as >6 months to become pregnant) and three perinatal outcomes: low birthweight (LBW; <2500 g), preterm birth (PTB; <37 weeks), and small-for-gestational-age (SGA; <10th percentile weight for given gestational age) using data from the Collaborative Perinatal Project. The study cohort was limited to pregnancies with a known time-to-pregnancy (n = 8465; 15%). Generalised estimating equations were used to estimate odds ratios (OR) and 95% confidence intervals [CI] for risk of adverse perinatal outcomes accounting for the clustering of pregnancy outcomes for women with more than one pregnancy. After adjusting for confounders, all ORs were close to the null (LBW, OR = 1.01; 95% CI = 0.86, 1.20), (PTB, OR = 1.10; 95% CI = 0.95, 1.27), (SGA, OR = 1.06; 95% CI = 0.91, 1.25). Thus, we found no evidence to support an adverse relationship between conception delay and decrements in gestation or birthweight among this select sample of fertile women, even after varying the cut-point for defining conception delay.     

Traffic-related air pollution, preterm birth and term birth weight in the PIAMA birth cohort study

Background

Maternal exposure to air pollution has been associated with adverse pregnancy outcomes. Few studies took into account the spatial and temporal variation of air pollution levels.

Objectives

To evaluate the impact of maternal exposure to traffic-related air pollution during pregnancy on preterm birth and term birth weight using a spatio-temporal exposure model.

Methods

We estimated maternal residential exposure to nitrogen dioxide (NO₂), particulate matter (PM_2.5) and soot during pregnancy (entire pregnancy, 1st trimester, and last month) for 3853 singleton births within the Dutch PIAMA prospective birth cohort study by means of temporally adjusted land-use regression models. Associations between air pollution concentrations and preterm birth and term birth weight were analyzed by means of logistic and linear regression models with and without adjustment for maternal physical, lifestyle, and socio-demographic characteristics.

Results

We found positive, statistically non-significant associations between exposure to soot during entire pregnancy and during the last month of pregnancy and preterm birth [adj. OR (95% CI) per interquartile range increase in exposure 1.08 (0.88–1.34) and 1.09 (0.93–1.27), respectively]. There was no indication of an adverse effect of air pollution exposure on term birth weight.

Conclusions

In this study, maternal exposure to traffic-related air pollution during pregnancy was not associated with term birth weight. There was a tendency towards an increased risk of preterm birth with increasing air pollution exposure, but statistical power was low.     

Francophone and Anglophone perinatal health: temporal and regional inequalities in a Canadian setting, 1981–2008

Objectives

We evaluated temporal and regional inequalities in adverse birth outcomes between Anglophones and Francophones of a Canadian province.

Methods

Odds ratios and rate differences in preterm birth (PTB, <37 gestational weeks) and small-for-gestational-age (SGA) birth were computed for Anglophones relative to Francophones for singleton live births in Québec from 1981 to 2008 (N?=?2,292,237), adjusting for maternal characteristics. Trends over time and residential region were evaluated.

Results

Rates of PTB and SGA birth overall were lower for Anglophones relative to Francophones, but temporal and regional trends varied by outcome. Although PTB rates increased over time, inequalities between Francophones and Anglophones were relatively stable. In contrast, inequalities in SGA birth narrowed over time as Francophone rates declined more than Anglophones. Inequalities in SGA birth favored Anglophones overall, but the gap gradually reversed in Montréal (the largest metropolitan center) to currently favor Francophones.

Conclusions

PTB and SGA birth rates favored Anglophones over Francophones. The linguistic gap was generally stable over time for PTB, but narrowed or reversed for SGA birth. Language may be used to capture inequalities in perinatal health in countries where different linguistic groups predominate.     

Lower birth weight and increased body fat at school age in children prenatally exposed to modern pesticides: a prospective study

Background

Evidence for an association between exposure during pregnancy to trihalomethanes (THMs) in drinking water and impaired fetal growth is still inconsistent and inconclusive, in particular, for various exposure routes. We examined the relationship of individual exposures to THMs in drinking water on low birth weight (LBW), small for gestational age (SGA), and birth weight (BW) in singleton births.

Methods

We conducted a cohort study of 4,161 pregnant women in Kaunas (Lithuania), using individual information on drinking water, ingestion, showering and bathing, and uptake factors of THMs in blood, to estimate an internal dose of THM. We used regression analysis to evaluate the relationship between internal THM dose and birth outcomes, adjusting for family status, education, smoking, alcohol consumption, body mass index, blood pressure, ethnic group, previous preterm, infant gender, and birth year.

Results

The estimated internal dose of THMs ranged from 0.0025 to 2.40 mg/d. We found dose-response relationships for the entire pregnancy and trimester-specific THM and chloroform internal dose and risk for LBW and a reduction in BW. The adjusted odds ratio for third tertile vs. first tertile chloroform internal dose of entire pregnancy was 2.17, 95% CI 1.19-3.98 for LBW; the OR per every 0.1 μg/d increase in chloroform internal dose was 1.10, 95% CI 1.01-1.19. Chloroform internal dose was associated with a slightly increased risk of SGA (OR 1.19, 95% CI 0.87-1.63 and OR 1.22, 95% CI 0.89-1.68, respectively, for second and third tertile of third trimester); the risk increased by 4% per every 0.1 μg/d increase in chloroform internal dose (OR 1.04, 95% CI 1.00-1.09).

Conclusions

THM internal dose in pregnancy varies substantially across individuals, and depends on both water THM levels and water use habits. Increased internal dose may affect fetal growth.     

Perinatal outcomes among immigrant mothers over two periods in a region of central Italy

Background

The number of immigrants has increased in Italy in the last twenty years (7.2% of the Italian population), as have infants of foreign-born parents, but scanty evidence on perinatal outcomes is available. The aim of this study was to investigate whether infants of foreign-born mothers living in Italy have different odds of adverse perinatal outcomes compared to those of native-born mothers, and if such measures changed over two periods.

Methods

The source of this area-based study was the regional hospital discharge database that records perinatal information on all births in the Lazio region. We analysed 296,739 singleton births born between 1996-1998 and 2006-2008. The exposure variable was the mother's region of birth. We considered five outcomes of perinatal health. We estimated crude and adjusted odds ratios and 95% confidence intervals (CIs) to evaluate the association between mother's region of birth and perinatal outcomes.

Results

Perinatal outcomes were worse among infants of immigrant compared to Italian mothers, especially for sub-Saharan and west Africans, with the following crude ORs (in 1996-1998 and 2006-2008 respectively): 1.80 (95%CI:1.44-2.28) and 1.95 (95%CI:1.72-2.21) for very preterm births, and 1.32 (95%CI:1.16-1.50) and 1.32 (95%CI:1.25-1.39) for preterm births; 1.18 (95%CI:0.99-1.40) and 1.17 (95%CI:1.03-1.34) for a low Apgar score; 1.22 (95%CI:1.15-1.31) and 1.24 (95%CI:1.17-1.32) for the presence of respiratory diseases; 1.47 (95%CI:1.30-1.66) and 1.45 (95%CI:1.34-1.57) for the need for special or intensive neonatal care/in-hospital deaths; and 1.03 (95%CI:0.93-1.15) and 1.07 (95%CI:1.00-1.15) for congenital malformations. Overall, time did not affect the odds of outcomes differently between immigrant and Italian mothers and most outcomes improved over time among all infants. None of the risk factors considered confounded the associations.

Conclusion

Our findings suggest that migrant status is a risk factor for adverse perinatal health. Moreover, they suggest that perinatal outcomes improved over time in some immigrant women. This could be due to a general improvement in immigrants' health in the past decade, or it may indicate successful application of policies that increase accessibility to mother-child health services during the periconception and prenatal periods for legal and illegal immigrant women in Italy.

     

Association between Local Traffic-Generated Air Pollution and Preeclampsia and Preterm Delivery in the South Coast Air Basin of California

Background

Preeclampsia is a major complication of pregnancy that can lead to substantial maternal and perinatal morbidity, mortality, and preterm birth. Increasing evidence suggests that air pollution adversely affects pregnancy outcomes. Yet few studies have examined how local traffic-generated emissions affect preeclampsia in addition to preterm birth.

Objectives

We examined effects of residential exposure to local traffic-generated air pollution on preeclampsia and preterm delivery (PTD).

Methods

We identified 81,186 singleton birth records from four hospitals (1997–2006) in Los Angeles and Orange Counties, California (USA). We used a line-source dispersion model (CALINE4) to estimate individual exposure to local traffic-generated nitrogen oxides (NO_x) and particulate matter < 2.5 μm in aerodynamic diameter (PM_2.5) across the entire pregnancy. We used logistic regression to estimate effects of air pollution exposures on preeclampsia, PTD (gestational age < 37 weeks), moderate PTD (MPTD; gestational age < 35 weeks), and very PTD (VPTD; gestational age < 30 weeks).

Results

We observed elevated risks for preeclampsia and preterm birth from maternal exposure to local traffic-generated NO_x and PM_2.5. The risk of preeclampsia increased 33% [odds ratio (OR) = 1.33; 95% confidence interval (CI), 1.18–1.49] and 42% (OR = 1.42; 95% CI, 1.26–1.59) for the highest NO_x and PM_2.5 exposure quartiles, respectively. The risk of VPTD increased 128% (OR = 2.28; 95% CI, 2.15–2.42) and 81% (OR = 1.81; 95% CI, 1.71–1.92) for women in the highest NO_x and PM_2.5 exposure quartiles, respectively.

Conclusion

Exposure to local traffic-generated air pollution during pregnancy increases the risk of preeclampsia and preterm birth in Southern California women. These results provide further evidence that air pollution is associated with adverse reproductive outcomes.     

Impact of maternal characteristics on the effect of maternal influenza vaccination on fetal outcomes

Background

Maternal infections during pregnancy have been associated with adverse fetal and infant health outcomes, and vaccination against influenza is the most effective tool to prevent morbidity and mortality due to seasonal and pandemic influenza. We evaluated the association between receipt of the inactivated seasonal influenza vaccine on preterm and small for gestational age (SGA) births, with the aim to assess racial and socioeconomic variations in vaccine effect.

Methods

We conducted a retrospective analysis of state-wide surveillance data from Georgia for the most recent four years available at the beginning of the study, a total of 8393 live births in Georgia from January 1, 2005 through December 31, 2008. We constructed multivariable logistic regression models and calculated odds ratios (OR) estimates with corresponding 95% confidence intervals (CI) to evaluate the effect of maternal influenza vaccination on SGA (birth weight <10th percentile for gestational age) and preterm (gestational age at birth <37 weeks) births while controlling for potential confounders.

Results

Among all women, we found significant strong associations between maternal influenza vaccination and reduced odds of a preterm birth during the widespread influenza activity period [OR = 0.39, 95% CI: 0.18, 0.83]. In this period, vaccination was protective against SGA births among women at higher risk for influenza related morbidity – women enrolled in the Women, Infant and Child (WIC) program [OR = 0.20, 95% CI: 0.04, 0.98] and Black women [OR = 0.15 95% CI: 0.02, 0.94]; maternal influenza vaccination was associated with reduced odds of a preterm birth among white women [OR = 0.34, 95% CI: 0.12, 0.91] and women of higher socio-economic status [OR = 0.30, 95% CI: 0.12, 0.74].

Conclusion

Influenza vaccination during pregnancy was significantly associated with reduced odds of small for gestational age and preterm births during the widespread influenza activity period. Vaccination effects varied by socio-demographic characteristics.     

Does Maternal Exposure to Secondhand Tobacco Smoke During Pregnancy Increase the Risk for Preterm or Small-for-Gestational Age Birth?

Introduction While associations between active smoking and various adverse birth outcomes (ABOs) have been reported in the literature, less is known about the impact of secondhand smoke (SHS) on many pregnancy outcomes. Methods We examined the relationship between maternal exposure to SHS during pregnancy and preterm (<?37 weeks gestation) and small-for-gestational age (SGA; assessed using sex-, race/ethnic-, and parity-specific growth curves) singleton births using non-smoking controls from the National Birth Defects Prevention Study (1997–2011). Multivariable logistic regression models for household, workplace/school, and combined SHS exposure—controlled for maternal education, race/ethnicity, pre-pregnancy body mass index, and high blood pressure—were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs). Interaction was assessed for maternal folic acid supplementation, alcohol use, age at delivery, and infant sex. Results Infants of 8855 mothers were examined in the preterm birth analysis with 666 (7.5%) categorized as preterm, 574 moderately preterm (32–36 weeks), and 92 very preterm (<?32 weeks). For the SGA analysis, infants of 8684 mothers were examined with 670 (7.7%) categorized as SGA. The aORs for mothers reporting both household and workplace/school SHS were elevated for preterm (aOR 1.99; 95% CI 1.13–3.50) and moderately preterm birth (32–36 weeks) (aOR 2.17; 95% CI 1.22–3.88). No results for the SGA analysis achieved significance, nor was evidence of interaction evident. Conclusion The findings suggest an association between SHS from multiple exposure sources and preterm birth, but no evidence for association with SGA births. Continued study of SHS and ABOs is needed to best inform public health prevention programs.     

兰州地区早产影响因素的研究

目的 探讨早产、自发性早产和医源性早产的相关高危因素.方法 回顾性调查2010年1月至2012年12月在甘肃省妇幼保健院住院分娩足月儿和早产儿的孕妇的住院资料,分娩足月活产儿5639例、早产儿540例,分为足月产组(≥37周孕龄)和早产组(<37周孕龄),比较早产组和足月产组发生早产的相关危险因素,以及自发性早产和医源性早产的相关高危因素.结果 ①Logistic回归分析发现教育年限(≥16年)(OR=0.61,95%CI:0.48~0.78)、家庭平均月收入(>3000元)(OR=0.62,95%CI:0.50~0.78)是早产发生的保护因素,而母亲妊娠合并症,比如妊娠期糖尿病(GDM)(OR=3.97,95%CI:1.70~9.25)、妊娠期高血压疾病(HDP)(OR=4.43,95%CI:3.35~5.87)、妊娠期胆汁淤积症(ICP)(OR=4.88,95%CI:3.25~7.32)是早产发生的独立高危因素.②按早产的病因分类,本研究中340例为自发性早产儿,余200例为医源性早产.经分层多因素非条件Logistic回归分析表明,与足月产相比,经产妇(OR=2.66,95%CI:1.87~3.76)、GDM(OR=4.52,95%CI:1.42~14.38),尤其是HDP孕妇(OR=14.19,95%CI:10.10~19.93)更易发生医源性早产,而ICP孕妇更多出现自发性流产(OR=12.875,95%CI:12.75~13.00).结论 应及早识别早产潜在的高危因素,加强围生期管理,以减少早产的发生,改善围生儿结局.     

Interpregnancy Interval and Risk of Adverse Pregnancy Outcomes: A Register-Based Study of 328,577 Pregnancies in Denmark 1994–2010

Objectives To investigate the associations of interpregnancy interval (IPI) with miscarriage, stillbirth, preterm delivery and small for gestational age delivery. Methods The study population comprised all women who had a live birth and at least one subsequent pregnancy in Denmark during the period from 1994 to 2010 (N?=?328,577). Linear regression was used to estimate risk differences for miscarriage, stillbirth, preterm delivery and small for gestational age delivery according to IPI. Results The results were heterogeneous: the risk of miscarriage increased monotonically with the length of the IPI. Compared to women with IPIs of 18–23 months, women with IPIs of 0–5 months experienced 18.7 (13.1–24.2) fewer miscarriages per 1000 pregnancies, while women with IPIs of ≥?60 months experienced 28.7 (23.4–34.0) more miscarriages per 1000 pregnancies. We found that women with IPIs of ≥?60 months had 1.7 (0.4–3.0) more stillbirths per 1000 births compared to women with IPIs of 18–23 months. U-shaped associations were seen for preterm delivery and small for gestational age delivery with women with IPIs of 18–23 months experiencing the lowest risks of these outcomes. Conclusions for Practice The heterogeneity in associations between IPI and adverse pregnancy outcomes suggests that different mechanisms of action may be at play at various times in the antepartum period. While the finding for miscarriage suggests that fecundity is an important determinant for IPI, the findings for preterm delivery and small for gestational age delivery suggest the coexistence of the maternal depletion syndrome mechanism and the physiological regression mechanism and the finding for stillbirth speaks against a strict maternal depletion syndrome explanation.     

Contrasting socioeconomic gradients in small for gestational age and preterm birth in Argentina, 2003–2007

Objectives

To examine the socioeconomic gradients in birth outcomes among singleton infants in Argentina, 2003–2007.

Methods

We analyzed data of 3,230,031 singleton infants born in 2003–2007, obtained from vital statistics. Associations between birth outcomes [small for gestational age (SGA), low birth weight (LBW), and preterm birth (PTB)] and socioeconomic indicators (maternal education and area-based material deprivation quintiles) were assessed with logistic regression.

Results

The risk of SGA increased with higher socioeconomic disadvantage, but that of PTB decreased. Compared to mothers who attained a tertiary or university degree, mothers who did not complete primary school were more likely to have a SGA infant [adjusted OR (95 % CI): 1.65 (1.62, 1.68)], but less likely to deliver preterm [0.92 (0.90, 0.94)]. As a result of the conflicting trends in SGA and PTB, LBW exhibited inconsistent socioeconomic gradients.

Conclusions

The excess risk of adverse birth outcomes associated with socioeconomic disadvantage was consistently reflected by SGA, but not by LBW and PTB. These findings challenge the usefulness of LBW as an indicator population health. Further research is needed to explain the reverse socioeconomic gradients in PTB.     

Iron deficiency anemia: Pregnancy outcomes with or without iron supplementation

Objective

To estimate the efficacy of iron supplementation in anemic pregnant women on the basis of occurrence of pregnancy complications and birth outcomes.

Methods

Comparison of the occurrence of medically recorded pregnancy complications and birth outcomes in pregnant women affected with medically recorded iron deficiency anemia and iron supplementation who had malformed fetuses/newborns (cases) and who delivered healthy babies (controls) in the population-based Hungarian Case-Control Surveillance System of Congenital Abnormalities.

Results

Of 22 843 cases with congenital abnormalities, 3242 (14.2%), while of 38 151 controls, 6358 (16.7%) had mothers with anemia. There was no higher rate of preterm births and low birth weight in the newborns of anemic pregnant women supplemented by iron. However, anemic pregnant women without iron treatment had a significantly shorter gestational age at delivery with a somewhat higher rate of preterm births but these adverse birth outcomes were prevented with iron supplementation. The rate of total and some congenital abnormalities was lower than expected and explained mainly by the healthier lifestyle and folic acid supplements. The secondary findings of the study showed a higher risk of constipation-related hemorrhoids and hypotension in anemic pregnant women with iron supplementation.

Conclusion

A higher rate of preterm birth was found in anemic pregnant women without iron treatment but this adverse birth outcome was prevented with iron supplementation. There was no higher rate of congenital abnormalities in the offspring of anemic pregnant women supplemented with iron and/or folic acid supplements.     

Maternal exposure to air pollution and birth outcomes

Background

The knowledge about air pollution effects on birth weight, prematurity, and small for gestational age (SGA) in low-exposure areas is insufficient.

Objectives

The aim of this birth cohort study was to investigate whether low-level exposure to air pollution was associated with prematurity and fetal growth and whether there are sex-specific effects.

Method

We combined high-quality registry information on 81,110 births with individually modeled exposure data at residence for nitrogen oxides (NO_x) and proximity to roads with differing traffic density. The data were analyzed by logistic and linear regression with and without potential confounders.

Results

We observed an increased risk for babies being SGA when we compared highest and lowest NO_x quartiles, adjusting for maternal age, smoking, sex, and year of birth. After additional adjustment for maternal country of origin and parity (which were highly intercorrelated), the increase was no longer statistically significant. However, in subgroup analyses when we compared highest and lowest NO_x quartiles we still observed an increased risk for SGA for girls [odds ratio (OR) = 1.12; 95% confidence interval (CI), 1.01–1.24); we also observed increased risk among mothers who had not changed residency during pregnancy (OR = 1.09; 95% CI, 1.01–1.18). The confounders with the greatest impact on SGA were parity and country of origin. Concerning prematurity, the prevalence was lower in the three higher NO_x exposure quartiles compared with the lowest category.

Conclusion

For future studies on air pollution effects on birth outcomes, careful control of confounding is crucial.     

Medical termination of pregnancy during the second versus the first trimester and its effects on subsequent pregnancy

Objective

The objective was to compare the risks of preterm birth, low birth weight, small for gestational age (SGA) infants and placental complications in subsequent pregnancy after second vs. first trimester medical termination of pregnancy (MTOP) in primigravid women.

Study Design

A total of 88,522 women who underwent termination of pregnancy during 2000–2009 were identified using Finnish health registers. Of them, primigravid women who underwent MTOP and had subsequent pregnancy ending in live birth up to the end of 2009 (n= 3843) were included in the study. The incidences and risks of preterm birth, low birth weight, SGA infants and placental complications after first- (n= 3427) vs. second-trimester MTOP (n= 416) were compared.

Results

Differences between the study groups in the incidences of preterm birth (3.9% in both groups), low birth weight (3.9% in the second- vs. 3.2% in the first-trimester group), SGA infants (2.4% vs. 2.5%) and placental complications (1.9% vs. 2.6%) were statistically insignificant. Second-trimester MTOP was associated with similar risks of preterm birth, low birth weight, SGA infants and placental complications compared with first-trimester MTOP after adjustment for background characteristics. After second-trimester MTOP, 51.2% of women underwent surgical evacuation, and 4.3% were diagnosed with infection. The differences in the risks of preterm birth, low birth weight, SGA infants and placental complications were statistically insignificant between women with vs. without these complications following second-trimester MTOP.

Conclusions

Second-trimester MTOP among primigravid women did not increase the risks of preterm birth, low birth weight, SGA infants or placental complications in subsequent pregnancy compared with first-trimester MTOP.

Implications

The present study suggests that medical termination of pregnancy in primigravid women during second vs. first trimester does not increase the risks of adverse outcomes in subsequent pregnancy and delivery. The data are of value when counseling women undergoing second-trimester TOP.     

Safety of inactivated monovalent pandemic (H1N1) 2009 vaccination during pregnancy: A population-based study in Taiwan

Background

Pregnant women were prioritized for H1N1 vaccination during the 2009–2010 pandemic. Safety concerns exist with vaccinating pregnant women, particularly in their first trimesters.

Methods

We linked computerized data on H1N1 vaccination, National Health Insurance, and Taiwan Birth Registry and identified events of spontaneous abortions (SABs) and all singleton births that occurred/delivered during November 1, 2009–September 30, 2010. The observation period for each case of SAB (6–19 weeks gestation) was divided into period at risk (1–28 days after vaccination) and control periods (the remaining person-days until SAB). The self-controlled case series method for truncated observational periods assessed the incidence rate ratio (IRR) of SAB during the 1–28 days compared with those in the control period. The case-control design matched each case of adverse fetal outcomes to up to 10 controls on fetal sex and year/month of pregnancy onset, and calculated matched odds ratio (OR) on H1N1 vaccination at <14 or ≥14 weeks gestation.

Results

Sixty-five women with SAB had received H1N1 vaccination at 6–19 weeks gestation. The IRR of SAB for the risk period 1–28 days was 1.03 (95% confidence interval [CI] 0.55–1.93). Among the 147,294 live births and 1354 stillbirths, maternal H1N1 vaccine receipt at <14 weeks gestation was associated with significantly reduced likelihood of small for gestational age (SGA) birth (OR 0.72, 95% CI 0.61–0.84) and birth defect (OR 0.46, 95% CI 0.22–1.00), whereas receipt at ≥14 weeks gestation was associated with significantly reduced likelihood of stillbirth (OR 0.63, 95% CI 0.46–0.86), prematurity (OR 0.90, 95% CI 0.83–0.97), low birth weight (OR 0.81, 95% CI 0.74–0.88), and SGA birth (OR 0.90, 95% CI 0.84–0.97).

Conclusions

H1N1 vaccination during pregnancy did not increase risk of SAB or adverse fetal outcomes.