Maternal Dietary Patterns and Birth Outcomes: A Systematic Review and Meta-Analysis

ABSTRACT Findings on the relations of maternal dietary patterns during pregnancy and risk of preterm birth and offspring birth size remain inconclusive. We aimed to systematically review and quantify these associations. We searched MEDLINE, Embase, CENTRAL, and CINAHL up to December 2017. Three authors independently conducted a literature search, study selection, data extraction, and quality assessment. Summary effect sizes were calculated with random effects models and studies were summarized narratively if results could not be pooled. We included 36 studies and pooled results from 25 observational studies (167,507 participants). Two common dietary patterns—“healthy” and “unhealthy”—were identified. Healthy dietary patterns—characterized by high intakes of vegetables, fruits, wholegrains, low-fat dairy, and lean protein foods—were associated with lower risk of preterm birth (OR for top compared with bottom tertile: 0.79; 95% CI: 0.68, 0.91; I2 = 32%) and a weak trend towards a lower risk of small-for-gestational-age (OR: 0.86; 95% CI: 0.73, 1.01; I2 = 34%). Only statistically data-driven healthy dietary patterns, and not dietary index-based patterns, were associated with higher birth weight (mean difference: 67 g; 95% CI: 37, 96 g; I2 = 75%). Unhealthy dietary patterns—characterized by high intakes of refined grains, processed meat, and foods high in saturated fat or sugar—were associated with lower birth weight (mean difference: −40 g; 95% CI: −61, −20 g; I2 = 0%) and a trend towards a higher risk of preterm birth (OR: 1.17; 95% CI: 0.99, 1.39; I2 = 76%). Data from observational studies indicate that greater adherence to healthy dietary patterns during pregnancy is significantly related to lower risk of preterm birth. No consistent associations with birth weight and small- or large-for-gestational-age were observed.

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Dietary patterns before and during pregnancy and birth outcomes: a systematic review

American Journal of Clinical Nutrition ◽

10.1093/ajcn/nqy353 ◽

2019 ◽

Vol 109 (Supplement_1) ◽

pp. 729S-756S ◽

Cited By ~ 14

Author(s):

Ramkripa Raghavan ◽

Carol Dreibelbis ◽

Brittany L Kingshipp ◽

Yat Ping Wong ◽

Barbara Abrams ◽

...

Keyword(s):

Birth Weight ◽

Preterm Birth ◽

Birth Outcomes ◽

Gestational Age ◽

Dietary Patterns ◽

Access To Health Care ◽

Spontaneous Preterm Birth ◽

Weight Outcomes ◽

Age And Sex ◽

Pregnancy And Birth

ABSTRACTBackgroundMaternal diet before and during pregnancy could influence fetal growth and birth outcomes.ObjectiveTwo systematic reviews aimed to assess the relationships between dietary patterns before and during pregnancy and 1) gestational age at birth and 2) gestational age- and sex-specific birth weight.MethodsLiterature was searched from January, 1980 to January, 2017 in 9 databases including PubMed, Embase, and Cochrane. Two analysts independently screened articles using predetermined inclusion and exclusion criteria. Data were extracted from included articles and risk of bias was assessed. Data were synthesized qualitatively, a conclusion statement was drafted for each question, and evidence supporting each conclusion was graded.ResultsOf the 9103 studies identified, 11 [representing 7 cohorts and 1 randomized controlled trial (RCT)] were included for gestational age and 21 (representing 19 cohorts and 2 RCTs) were included for birth weight. Limited but consistent evidence suggests that certain dietary patterns during pregnancy are associated with a lower risk of preterm birth and spontaneous preterm birth. These protective dietary patterns are higher in vegetables; fruits; whole grains; nuts, legumes, and seeds; and seafood (preterm birth, only), and lower in red and processed meats, and fried foods. Most of the research was conducted in healthy Caucasian women with access to health care. No conclusion can be drawn on the association between dietary patterns during pregnancy and birth weight outcomes. Although research is available, the ability to draw a conclusion is restricted by inconsistency in study findings, inadequate adjustment of birth weight for gestational age and sex, and variation in study design, dietary assessment methodology, and adjustment for key confounding factors. Insufficient evidence exists regarding dietary patterns before pregnancy for both outcomes.ConclusionsMaternal dietary patterns may be associated with a lower preterm and spontaneous preterm birth risk. The association is unclear for birth weight outcomes.

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The duration of estrogen treatment before progesterone application does not affect neonatal and perinatal outcomes in single frozen blastocyst transfer cycles

10.21203/rs.3.rs-877891/v1 ◽

2021 ◽

Author(s):

Mingze Du ◽

Junwei Zhang ◽

Xiaona Yu ◽

Jiaheng Li ◽

Xinmi Liu ◽

...

Keyword(s):

Birth Weight ◽

Preterm Birth ◽

Gestational Age ◽

Treatment Duration ◽

Statistical Significance ◽

Perinatal Outcomes ◽

Perinatal Period ◽

Estrogen Treatment ◽

Blastocyst Transfer ◽

Large For Gestational Age

Abstract Background: The number of frozen embryo transfer (FET) cycles has substantially increased in the past decade. Preparing the endometrium in artificial cycles is widely used in clinical practice. Therefore, how to optimize this program, improve the clinical outcome and ensure the safety of the perinatal period is the focus of our attention. The purpose of this study was to explore whether the duration of estrogen treatment before progesterone application affects neonatal and perinatal outcomes in single frozen blastocyst transfer cycles.Methods: It was a retrospective cohort study. Patients receiving single frozen blastocyst transfer and delivering a single live birth between January 2015 and December 2019 were included. Primary outcome was small for gestational age (SGA). Secondary outcomes were neonatal birthweight, gestational weeks at delivery, preterm birth, low birth weight (LBW), macrosomia, large for gestational age (LGA), neonatal malformation and rate of pregnancy-related complications.Cycles were allocated to four groups according to the estrogen-treatment duration before single frozen blastocyst transfer ①≤12 days (n=306), ②13-15 days (n=620), ③16-18 days (n=471), ④≥19 days (n=275).Results: In total, 1672 cycles were analyzed. Cycles were allocated to four groups according to the estrogen-treatment duration before single frozen blastocyst transfer ①≤12 days (n=306), ②13-15 days (n=620), ③16-18 days (n=471), ④≥19 days (n=275). The rates of SGA among the four groups were 7.8% (24/306), 4.8% (30/620), 5.7% (27/471), and 7.6% (21/275), with no statistical significance (P=0.20). Other neonatal outcomes, including mean neonatal birth weight, gestational weeks at delivery, preterm birth rate, LBW, macrosomia, LGA and neonatal malformation, were comparable among the groups (P=0.38, P=0.16, P=0.20, P=0.58, P=0.20, P=0.34, P=0.96). The rate of pregnancy-related complications was similar among the groups. Multiple logistics regression showed that the duration of estrogen treatment did not affect the rate of singleton SGA (13-15 days, AOR=1.37, 95% CI= 0.70-2.70, P=0.36; 16-18 days, AOR=0.74, 95% CI= 0.40-1.36, P=0.34; ≥19 days, AOR=0.81, 95% CI= 0.44-1.49, P=0.50).Conclusion: The estrogen-treatment duration before progesterone application does not affect neonatal and perinatal outcomes in single frozen blastocyst transfer cycles.

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P–775 Obstetric and perinatal outcomes of singleton pregnancies after blastocyst-stage embryo transfer: a systematic review and cumulative meta-analysis

Human Reproduction ◽

10.1093/humrep/deab130.774 ◽

2021 ◽

Vol 36 (Supplement_1) ◽

Author(s):

N Marconi ◽

C Allen ◽

S Bhattacharya ◽

A Maheshwari

Keyword(s):

Systematic Review ◽

Preterm Birth ◽

Embryo Transfer ◽

Gestational Age ◽

Lower Risk ◽

Meta Analysis ◽

Blastocyst Stage ◽

Cleavage Stage ◽

Stage Embryo ◽

Singleton Pregnancies

Abstract Study question Are obstetric/perinatal outcomes different in singleton pregnancies following blastocyst-stage embryo transfer when compared to cleavage-stage embryo transfer and have results changed over time? Summary answer Pregnancies following blastocyst are consistently associated with higher risk of large for gestational age and lower risk of small for gestational age babies What is known already Extended embryo culture to blastocyst-stage is widely used to select best embryos in in vitro fertilisation (IVF) cycles to improve pregnancy rates. Transfer of blastocyst-stage embryos is increasing with this being the default strategy in most clinics. As blastocysts are kept in culture until day 5, 6 or 7 after oocyte fertilisation, there are suggestions that longer exposure to culture media may have a negative impact on pregnancy outcomes. More recent primary studies have challenged some of the initial findings. We therefore conducted an updated systematic review and cumulative meta-analysis (CMA) to examine if these results have changed over time. Study design, size, duration Systematic review of studies published between 1980 and 2020, followed by aggregated meta-analysis and CMA to track the accumulation of evidence over the period of time. Exposed group: singleton pregnancies following blastocyst transfer. Non-exposed group: singleton pregnancies following cleavage-stage transfer. Sub-group analyses were conducted on fresh and frozen-thawed embryo transfers. Perinatal (categories of preterm birth and birth weight) and obstetric outcomes (hypertensive disorders of pregnancy, gestational diabetes, c-section, placental anomalies) were compared between the groups. Participants/materials, setting, methods Medline, EMBASE, CINHAL, Web of Science, Cochrane Central Register of Clinical Trials and International Clinical Trials Registry Platform databases were searched. Relevant journals were searched for advance access publications. Critical Appraisal Skills Programme (CASP) checklists were used to assess study quality. Two independent reviewers extracted data in 2 × 2 tables. Aggregated and CMA were performed using Comprehensive Meta-Analysis software. Risk ratio (RR) with 95% confidence interval (CI) were calculated. Main results and the role of chance A total of 33 observational studies were included (n = 574,756 singleton pregnancies). Pregnancies following blastocyst-stage embryo transfer are associated with a higher risk of preterm birth (PTB) (RR 1.09; 95% CI 1.01–1.17), very preterm birth (VPTB) (RR 1.15; 95% CI 1.07–1.24), large for gestational age (LGA) babies (RR 1.13; 95% CI 1.08–1.19), c-section (RR 1.05; 95% CI 1.02–1.09), and with a lower risk of small for gestational age (SGA) babies (RR 0.86; 95% CI 0.81–0.93) as compared to singleton pregnancies following cleavage-stage embryo transfer. These findings were maintained in both fresh and frozen-thawed sub-groups for LGA and SGA. PTB was not significantly different in both sub-group analyses. The risk of VPTB was higher after blastocyst-stage embryo transfer only in the sub-group analysis of fresh embryo transfers (RR 1.17; 95% CI 1.09–1.27) and that of c-section only in the frozen-thawed sub-group (RR 1.08; 95% CI 1.04–1.12). No other statistically significant differences for the other outcomes were noted. The CMA suggests that for SGA and LGA subsequent studies have increased the precision of the point estimate with no change in the direction or magnitude of the treatment effect since 2014. Limitations, reasons for caution This analysis was constrained by the intrinsic limitations of observational studies with some of them receiving a CASP score < 10. Adjustment for confounders was not possible and a high degree of clinical and statistical heterogeneity was noted among studies. Wider implications of the findings: Blastocyst is associated with a higher risk of LGA and a lower risk of SGA with a stable body of evidence since 2014. We may need to revisit the default position of extending embryo culture and individualise care, until further high-quality data from individual-patient-data of large registries are available. Trial registration number Not applicable

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Impact of Obesity on Perinatal Outcomes among Asthmatic Women

Canadian Respiratory Journal ◽

10.1155/2013/815143 ◽

2013 ◽

Vol 20 (5) ◽

pp. 345-350 ◽

Cited By ~ 3

Author(s):

Meggie Thuot ◽

Marc-André Coursol ◽

Sonia Nguyen ◽

Vanessa Lacasse-Guay ◽

Marie-France Beauchesne ◽

...

Keyword(s):

Body Mass Index ◽

Birth Weight ◽

Preterm Birth ◽

Body Mass ◽

Gestational Age ◽

Small For Gestational Age ◽

Perinatal Outcomes ◽

Normal Weight ◽

Large For Gestational Age ◽

Obese Women

BACKGROUND: Only one study has investigated the combined effect of maternal asthma and obesity on perinatal outcomes; however, it did not consider small-for-gestational age and large-for-gestational age infants.OBJECTIVES: To examine the impact of obesity on perinatal outcomes among asthmatic women.METHODS: A cohort of 1386 pregnancies from asthmatic women was reconstructed using three of Quebec’s administrative databases and a questionnaire. Women were categorized using their prepregnancy body mass index. Underweight, overweight and obese women were compared with normal weight women. The primary outcome was the birth of a small-for-gestational-age infant, defined as a birth weight below the 10th percentile for gestational age and sex. Secondary outcomes were large-for-gestational-age infants (birth weight >90th percentile for gestational age) and preterm birth (<37 weeks’ gestation). Logistic regression models were used to obtain the ORs of having small-for-gestational-age infants, large-for-gestational-age infants and preterm birth as a function of body mass index.RESULTS: The proportions of underweight, normal weight, overweight and obese women were 10.8%, 53.3%, 19.7% and 16.2%, respectively. Obese asthmatic women were not found to be significantly more at risk for giving birth to small-for-gestational-age infants (OR 0.6 [95% CI 0.4 to 1.1]), large-for-gestational-age infants (OR 1.2 [95% CI 0.7 to 2.2]) or having a preterm delivery (OR 0.7 [95% CI 0.4 to 1.3]) than normal-weight asthmatic women.CONCLUSIONS: No significant negative interaction between maternal asthma and obesity on adverse perinatal outcomes was observed.

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Effect of maternal weight gain according to the Institute of Medicine recommendations on pregnancy outcomes in a Chinese population

Journal of International Medical Research ◽

10.1177/0300060519861463 ◽

2019 ◽

Vol 47 (9) ◽

pp. 4397-4412 ◽

Cited By ~ 2

Author(s):

Ping Guan ◽

Fei Tang ◽

Guoqiang Sun ◽

Wei Ren

Keyword(s):

Weight Gain ◽

Birth Weight ◽

Preterm Birth ◽

Low Birth Weight ◽

Gestational Age ◽

Pregnancy Outcomes ◽

Adverse Outcomes ◽

Large For Gestational Age ◽

Maternal Weight ◽

Increased Risk

Objective This study aimed to analyze the effects of maternal weight on adverse pregnancy outcomes. Methods Data were retrospectively collected from a hospital in Wuhan, China. A total of 1593 pregnant women with singletons were included. Adverse outcomes during pregnancy, such as small for gestational age (SGA), large for gestational age (LGA), and hypertensive disorders in pregnancy (HDP) were analyzed. Results The risks of low birth weight, SGA, and preterm birth were significantly higher in the inadequate gestational weight gain (GWG) group compared with the adequate GWG group. GWG over the guidelines was related to a higher risk of macrosomia, LGA, cesarean section, and HDP than GWG within the guidelines. The risks of low birth weight (OR = 5.082), SGA (OR = 3.959), preterm birth (OR = 3.422), and gestational diabetes mellitus (OR = 1.784) were significantly higher in women with a normal pre-pregnancy body mass index (BMI) and inadequate GWG compared with women with a normal pre-pregnancy BMI and adequate GWG. The risks of macrosomia (OR = 3.654) and HDP (OR = 1.992) were increased in women with normal pre-pregnancy BMI and excessive GWG. Conclusion Women with an abnormal BMI and inappropriate GWG have an increased risk of adverse maternal and infant outcomes. Weight management during the perinatal period is required.

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Effects of maternal diets on preterm birth and low birth weight: a systematic review

British Journal Of Nutrition ◽

10.1017/s0007114519002897 ◽

2019 ◽

Vol 123 (4) ◽

pp. 446-461

Author(s):

Dereje G. Gete ◽

Michael Waller ◽

Gita D. Mishra

Keyword(s):

Birth Weight ◽

Preterm Birth ◽

Low Birth Weight ◽

Diet Quality ◽

Dietary Patterns ◽

Dairy Products ◽

Lower Risk ◽

Whole Grains ◽

High Intake ◽

High Consumption

AbstractCurrent evidence indicates that maternal diets before and during pregnancy could influence rates of preterm birth, low birth weight (LBW) and small for gestational age (SGA) births. However, findings have been inconsistent. This review summarised evidence concerning the effects of maternal diets before and during pregnancy on preterm birth, LBW and SGA. Systematic electronic database searches were carried out using PubMed, Embase, Scopus and Cochrane library using the preferred reporting items for systematic reviews and meta-analyses guidelines. The review included forty eligible articles, comprising mostly of prospective cohort studies, with five randomised controlled trials. The dietary patterns during pregnancy associated with a lower risk of preterm birth were commonly characterised by high consumption of vegetables, fruits, whole grains, fish and dairy products. Those associated with a lower risk of SGA also had similar characteristics, including high consumption of vegetables, fruits, legumes, seafood/fish and milk products. Results from a limited number of studies suggested there was a beneficial effect on the risk of preterm birth of pre-pregnancy diet quality characterised by a high intake of fruits and proteins and less intake of added sugars, saturated fats and fast foods. The evidence was mixed for the relationship between maternal dietary patterns during pregnancy and LBW. These findings indicate that better maternal diet quality during pregnancy, characterised by a high intake of vegetables, fruits, whole grains, dairy products and protein diets, may have a synergistic effect on reducing the risk of preterm birth and SGA.

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Dietary patterns and chronic kidney disease risk: a systematic review and updated meta-analysis of observational studies

Nutrition Journal ◽

10.1186/s12937-020-00661-6 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Ling-Qiong He ◽

Xu-Hong Wu ◽

Yi-Qian Huang ◽

Xiao-Yan Zhang ◽

Long Shu

Keyword(s):

Systematic Review ◽

Chronic Kidney Disease ◽

Kidney Disease ◽

Dietary Patterns ◽

Dietary Pattern ◽

Lower Risk ◽

Observational Studies ◽

Meta Analysis ◽

Drinking Pattern ◽

Healthy Dietary Pattern

Abstract Background A number of studies have reported the association between dietary patterns and the risk of chronic kidney disease (CKD), however a consistent perspective hasn’t been established to date. Herein, we conducted this systematic review and meta-analysis of observational studies to assess the association between dietary patterns and CKD. Methods MEDLINE, EBSCO and references from eligible studies were searched for relevant articles published up to 9 May 2020 that examined the association of common dietary patterns and CKD. The heterogeneity among studies was assessed by Cochran’s Q test and I2 methods. Results Seventeen eligible studies, involving 149,958 participants, were included in our systematic review and meta-analysis. The highest compared with the lowest category of healthy dietary pattern was significantly associated with a lower risk of CKD (OR=0.69; CI: 0.57, 0.84; P=0.0001). A higher risk of CKD was shown for the highest compared with the lowest categories of Western-type dietary pattern (OR=1.86; CI: 1.21, 2.86; P=0.005). There were evidence of a lower risk of CKD in the highest compared with the lowest categories of light-moderate drinking pattern (OR=0.76; CI: 0.71, 0.81; P< 0.0001) and heavy drinking pattern (OR=0.67; CI: 0.56, 0.80; P< 0.0001). Conclusions The results of this systematic review and meta-analysis show that a healthy dietary pattern and alcohol drinking were associated with lower risk of CKD, whereas a Western-type dietary pattern was associated with higher risk of CKD.

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Adherence to healthy dietary pattern and risk of kidney disease: a systematic review and meta-analysis of observational studies

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000647 ◽

2020 ◽

pp. 1-13

Author(s):

Sepideh Soltani ◽

Ahmad Jayedi

Keyword(s):

Kidney Disease ◽

Dietary Patterns ◽

Dietary Pattern ◽

Lower Risk ◽

Observational Studies ◽

Meta Analysis ◽

Data Driven ◽

Inverse Association ◽

Cross Sectional ◽

Healthy Dietary Pattern

Abstract. Epidemiological studies show that adherence to healthy dietary patterns may be associated with a lower risk of decline in kidney function. However, existing evidence has not been quantitatively gathered. Pertinent observational studies investigating the association of adherence to a healthy dietary pattern, either priori-defined dietary pattern/indices or data-driven dietary patterns, with risk of kidney disease in the general population were identified by searching Medline and Scopus databases to May 28, 2018. A random-effects meta-analysis was applied. The analysis included eight prospective cohorts (5734 cases among 569,688 participants) and five cross-sectional studies (1955 cases among 16,614 participants). Higher adherence to a healthy dietary pattern (either priori-defined or data-driven dietary patterns) was associated with a 28% lower risk of kidney disease in the analysis of prospective cohort studies (RR = 0.72, 95 % CI = 0.58, 0.86; I2 = %71, n = 8). A subgroup analysis based on definition of healthy dietary pattern resulted in significant inverse association only in the subgroup of Dietary Approaches to Stop Hypertension dietary pattern (RR: 0.74, 95 % CI: 0.54, 0.93; I2 = 73%, n = 5). A dose-response analysis indicated a monotonic inverse association between adherence to the Dietary Approaches to Stop Hypertension dietary pattern with risk of kidney disease. A 32% lower risk was observed in the analysis of cross-sectional studies (OR: 0.68, 95 %CI: 0.53, 0.83, I2 = 0%, n = 5). The findings suggest that higher adherence to a healthy dietary pattern is associated with a lower risk of kidney disease.

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Prepregnancy dietary patterns and risk of preterm birth and low birth weight: findings from the Australian Longitudinal Study on Women's Health

American Journal of Clinical Nutrition ◽

10.1093/ajcn/nqaa057 ◽

2020 ◽

Vol 111 (5) ◽

pp. 1048-1058

Author(s):

Dereje G Gete ◽

Michael Waller ◽

Gita D Mishra

Keyword(s):

Longitudinal Study ◽

Birth Weight ◽

Preterm Birth ◽

Low Birth Weight ◽

Women's Health ◽

Dietary Patterns ◽

Lower Risk ◽

Factor Analyses ◽

Spontaneous Preterm Birth ◽

Australian Longitudinal Study

ABSTRACT Background Findings from previous studies on associations between prepregnancy dietary patterns and preterm birth and low birth weight (LBW) are limited and inconsistent. Objectives To examine the association between prepregnancy dietary patterns and the risk of preterm birth and LBW. Methods This study included 3422 and 3508 singleton live births from the Australian Longitudinal Study on Women's Health (ALSWH) for the analyses of preterm birth and LBW, respectively. We included women who were nulliparous and nonpregnant at baseline surveys. We used factor analyses and the Healthy Eating Index-2015 (HEI-2015) score to derive maternal dietary patterns. Four dietary patterns were identified with factor analyses: meats and high-fats; prudent diets; sugar, refined grains, and processed foods; and traditional vegetables. Preterm birth and LBW were assessed using maternal reports from ALSWH data between 2003 and 2015. Multivariable logistic regression analyses were used. Results Greater adherence to the traditional vegetables pattern before pregnancy was associated with a lower risk of preterm birth and spontaneous preterm birth after adjustments for lifestyle factors and pregnancy complications, highest compared with lowest tertile (adjusted OR = 0.72, 95% CI: 0.53, 0.99) and (RR ratio = 0.62, 95% CI: 0.39, 1.00), respectively. However, these associations were attenuated by the prepregnancy BMI. No significant associations were observed between prepregnancy dietary patterns and LBW. Conclusion This study suggests that better adherence to the traditional vegetables pattern before pregnancy is associated with a lower risk of preterm birth, particularly spontaneous preterm birth among nulliparous women. This finding warrants further examination.

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Hemoglobin Concentration and Pregnancy Outcomes: A Systematic Review and Meta-Analysis

BioMed Research International ◽

10.1155/2013/769057 ◽

2013 ◽

Vol 2013 ◽

pp. 1-9 ◽

Cited By ~ 21

Author(s):

Bunyarit Sukrat ◽

Chumpon Wilasrusmee ◽

Boonying Siribumrungwong ◽

Mark McEvoy ◽

Chusak Okascharoen ◽

...

Keyword(s):

Systematic Review ◽

Birth Weight ◽

Preterm Birth ◽

Low Birth Weight ◽

Gestational Age ◽

Pregnancy Outcomes ◽

Meta Analysis ◽

First Trimester ◽

Third Trimester ◽

The Third

Objective. To conduct a systematic review and meta-analysis of hemoglobin effect on the pregnancy outcomes.Methods. We searched MEDLINE and SCOPUS from January 1, 1990 to April 10, 2011. Observational studies addressing association between hemoglobin and adverse pregnancy outcomes were selected. Two reviewers independently extracted data. A mixed logistic regression was applied to assess the effects of hemoglobin on preterm birth, low birth weight, and small for gestational age.Results. Seventeen studies were included in poolings. Hemoglobin below 11 g/dL was, respectively, 1.10 (95% CI: 1.02–1.19), 1.17 (95% CI: 1.03–1.32), and 1.14 (95% CI: 1.05–1.24) times higher risk of preterm birth, low birth weight, and small for gestational age than normal hemoglobin in the first trimester. In the third trimester, hemoglobin below 11 g/dL was 1.30 (95% CI: 1.08–1.58) times higher risk of low birth weight. Hemoglobin above 14 g/dL in third trimester decreased the risk of preterm term with ORs of 0.50 (95% CI: 0.26–0.97), but it might be affected by publication bias.Conclusions. Our review suggests that hemoglobin below 11 g/dl increases the risk of preterm birth, low birth weight, and small gestational age in the first trimester and the risk of low birth weight in the third trimester.

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