scholarly journals Relation of Hemoglobin Measured at Different Times in Pregnancy to Preterm Birth and Low Birth Weight in Shanghai, China

1998 ◽  
Vol 148 (10) ◽  
pp. 998-1006 ◽  
Author(s):  
L.-M. Zhou ◽  
W.-W. Yang ◽  
J.-Z. Hua ◽  
C.-Q. Deng ◽  
X. Tao ◽  
...  
Author(s):  
Giovanni Corrao ◽  
Federico Rea ◽  
Matteo Franchi ◽  
Benedetta Beccalli ◽  
Anna Locatelli ◽  
...  

This study aimed to illustrate and account for immortal time bias in pregnancy observational investigations, using the relationship between late use of antibiotics and risk of preterm birth as an example. We conducted a population-based cohort study including 549,082 deliveries between 2007 and 2017 in Lombardy, Italy. We evaluated the risk of preterm births, low birth weight, small for gestational age, and low Apgar score associated with antibiotic dispensing during the third trimester of pregnancy. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CI) of the outcomes, considering the use of antibiotics as time-fixed (with biased classification of exposure person-time) and time-varying (with proper classification of exposure person-time) exposure. There were 23,638 (4.3%) premature deliveries. There was no association between time-fixed exposure to antibiotics and preterm delivery (adjusted HR 0.96; 95% CI 0.92 to 1.01) but an increased risk of preterm birth when time-varying exposure to antibiotics was considered (1.27; 1.21 to 1.34). The same trend was found for low birth weight and low Apgar score. Immortal time bias is a common and sneaky trap in observational studies involving exposure in late pregnancy. This bias could be easily avoided with suitable design and analysis.


BMJ ◽  
2020 ◽  
pp. m3811
Author(s):  
Matthew Francis Chersich ◽  
Minh Duc Pham ◽  
Ashtyn Areal ◽  
Marjan Mosalam Haghighi ◽  
Albert Manyuchi ◽  
...  

Abstract Objective To assess whether exposure to high temperatures in pregnancy is associated with increased risk for preterm birth, low birth weight, and stillbirth. Design Systematic review and random effects meta-analysis. Data sources Medline and Web of Science searched up to September 2018, updated in August 2019. Eligibility criteria for selecting studies Clinical studies on associations between high environmental temperatures, and preterm birth, birth weight, and stillbirths. Results 14 880 records and 175 full text articles were screened. 70 studies were included, set in 27 countries, seven of which were countries with low or middle income. In 40 of 47 studies, preterm births were more common at higher than lower temperatures. Exposures were classified as heatwaves, 1°C increments, and temperature threshold cutoff points. In random effects meta-analysis, odds of a preterm birth rose 1.05-fold (95% confidence interval 1.03 to 1.07) per 1°C increase in temperature and 1.16-fold (1.10 to 1.23) during heatwaves. Higher temperature was associated with reduced birth weight in 18 of 28 studies, with considerable statistical heterogeneity. Eight studies on stillbirths all showed associations between temperature and stillbirth, with stillbirths increasing 1.05-fold (1.01 to 1.08) per 1°C rise in temperature. Associations between temperature and outcomes were largest among women in lower socioeconomic groups and at age extremes. The multiple temperature metrics and lag analyses limited comparison between studies and settings. Conclusions Although summary effect sizes are relatively small, heat exposures are common and the outcomes are important determinants of population health. Linkages between socioeconomic status and study outcomes suggest that risks might be largest in low and middle income countries. Temperature rises with global warming could have major implications for child health. Systematic review registration PROSPERO CRD 42019140136 and CRD 42018118113.


2021 ◽  
Vol 8 (29) ◽  
pp. 2609-2614
Author(s):  
Pradeep Kumar M ◽  
Mayadevi Brahmanandan ◽  
Dini S.B

BACKGROUND Multiple micronutrient deficiencies commonly coexist in pregnancy and may play a role in the pathogenesis of many high-risk events in pregnancy. Mineral estimation during the first and second trimester may help in the identification of high-risk pregnancies predisposed to pre-eclampsia, preterm birth or low birth weight. Body mass index (BMI) is an independent risk factor influencing the serum levels of micronutrients like iron, calcium, phosphorous and magnesium. The purpose of this study was to compare the serum levels of iron, magnesium, calcium and phosphorus during first & second trimesters of pregnancy and their correlation with body mass index and adverse pregnancy outcomes. METHODS This was a longitudinal descriptive study, done over a period of twelve months, from April 2017 to March 2018. 94 low risk pregnant women were selected in the first trimester, and they were followed up for the entire duration of pregnancy. 2 ml of blood is collected at first and second trimester and analysed for the serum levels of iron (µg/dl), magnesium (mg/dl), calcium (mg/dl) and inorganic phosphorus (mg/dl). Mean values of these elements were noted and BMI was measured. Patients were followed up to observe the pregnancy outcome, especially development of hypertension, preterm birth and low birth weight. The data were subjected to suitable statistical analyses. P value less than 0.05 is considered as statistically significant. RESULTS Mean values of Ca, Mg, inorganic P and Fe were 9.3 mg/dl ± 0.52, 1.79 mg/dl ± 0.28, 3.59 mg/dl ± 0.54 and 83.7 µg/dl ± 25.36 respectively in first trimester and 8.9 mg/dl ± 0.47, 1.62 mg/dl ± 0.16, 3.17 mg/dl ± 0.44 and 76.17 µg/dl ± 21. 69 respectively in the second trimester. Hypocalcaemia was noted in 12.7 % and 38.3 % in the first and second trimester respectively. Hypomagnesaemia was seen in 51.1 % and 80.9 % in the first and second trimester respectively. Hypophosphatemia was seen in 3.2 % and 14.8 % in the first and second trimester respectively. These findings were statistically significant. There was no significant change in the iron levels in the present study. 19.1 % were underweight. 56.4 % had normal BMI. 19.2 % were overweight. 5.3 % were obese. CONCLUSIONS There is no correlation between serum values of trace elements and the BMI of study subjects. Even though significant hypocalcaemia, hypophosphatemia and hypomagnesaemia was noted in second trimester compared to first, there was no predisposition to the development of adverse outcomes like pre-eclampsia, preterm birth or low birth weight. This may be the effect of dietary and pharmacological supplementation during pregnancy. KEYWORDS Micronutrients, Pregnancy Complications, Calcium, Phosphorus, Magnesium, Iron


2014 ◽  
Vol 36 (1) ◽  
pp. 13-18 ◽  
Author(s):  
Hsiang Huang ◽  
Shane Coleman ◽  
Jeffrey A. Bridge ◽  
Kimberly Yonkers ◽  
Wayne Katon

PLoS ONE ◽  
2014 ◽  
Vol 9 (7) ◽  
pp. e100247 ◽  
Author(s):  
Marcus J. Rijken ◽  
Alysha M. De Livera ◽  
Sue J. Lee ◽  
Machteld E. Boel ◽  
Suthatsana Rungwilailaekhiri ◽  
...  

2016 ◽  
Vol 44 (3) ◽  
Author(s):  
Wolf Kirschner ◽  
Joachim W. Dudenhausen ◽  
Wolfgang Henrich

AbstractThe conditions of iron deficiency are highly incident in pregnancy with elevated risks for preterm birth and low birth weight. In our recent study, we found 6% of participants having anemia, whereas between 39% and 47% showed iron deficiency without anemia. In many countries in prenatal care solely hemoglobin (Hb) measurement is applied. For the gynecologists till date there is no indication to determine other markers (e.g., serum-ferritin). As iron deficiency results from an imbalance between intake and loss of iron, our aim was to find out if the risk of iron deficiency conditions can be estimated by a diet history protocol as well as questionnaires to find about iron loss. We found that the risk of having iron deficiency in upper gestational week (>=21) increased by a factor of five. Thus, additional diagnostics should be done in this group by now. Using the questionnaire as a screening instrument, we further estimated the probability of disease in terms of a positive likelihood ratio (LR+). The positive LR for the group below 21


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