The interleukins IL-6 and IL-1Ra: a mediating role in the associations between BMI and birth weight?

Inflammatory markers in pregnancy - surprisingly stable. Mapping trajectories and drivers in four large cohorts

Adaptations of the immune system throughout gestation have been proposed as important mechanisms regulating successful pregnancy. Dysregulation of the maternal immune system has been associated with adverse maternal and fetal outcomes. To translate findings from mechanistic preclinical studies to human pregnancies, studies of serum immune markers are the mainstay. The design and interpretation of human biomarker studies require additional insights in the trajectories and drivers of peripheral immune markers. The current study mapped maternal inflammatory markers (C-reactive protein (CRP), interleukin (IL)-1β, IL-6, IL-17A, IL-23, interferon- γ ) during pregnancy and investigated the impact of demographic, environmental and genetic drivers on maternal inflammatory marker levels in four multi-ethnic and socio-economically diverse population-based cohorts with more than 12,000 pregnant participants. Additionally, pregnancy inflammatory markers were compared to pre-pregnancy levels. Cytokines showed a high correlation with each other, but not with CRP. Inflammatory marker levels showed high variability between individuals, yet high concordance within an individual over time during and pre-pregnancy. Pre-pregnancy body mass index (BMI) explained more than 9.6% of the variance in CRP, but less than 1% of the variance in cytokines. The polygenic score of CRP was the best predictor of variance in CRP (>14.1%). Gestational age and previously identified inflammation drivers, including tobacco use and parity, explained less than 1% of variance in both cytokines and CRP. Our findings corroborate differential underlying regulatory mechanisms of CRP and cytokines and are suggestive of an individual inflammatory marker baseline which is, in part, genetically driven. While prior research has mainly focused on immune marker changes throughout pregnancy, our study suggests that this field could benefit from a focus on intra-individual factors, including metabolic and genetic components.

Changes in Serum Cytokines Throughout Pregnancy in Women With Polycystic Ovary Syndrome

CONTEXT

Polycystic ovary syndrome (PCOS) is a common endocrine disorder associated with low-grade inflammation and increased incidence of pregnancy complications, but its influence on the maternal immune system in pregnancy is unknown. Longitudinal serum cytokine profiling is a sensitive measure of the complex immunological dynamics of pregnancy.

OBJECTIVE

This work aimed to determine the immunological dynamics of serum cytokines throughout pregnancy in women with PCOS and compare it to pregnancy in women without PCOS.

METHODS

A post hoc analysis was conducted of longitudinal serum samples from 2 randomized, placebo-controlled multicenter studies of pregnant women with PCOS and 2 studies of pregnant women without PCOS. Pregnant women with PCOS (n = 358) and without PCOS (n = 258, controls) provided 1752 serum samples from 4 time points in pregnancy (weeks 10, 19, 32, and 36). Main outcome measures included maternal serum levels of 22 cytokines and C-reactive protein (CRP) at 4 time points in pregnancy.

RESULTS

Women with PCOS showed marked immunological changes in serum cytokines throughout pregnancy. Compared to controls, women with PCOS showed higher levels of 17 cytokines and CRP at week 10 of pregnancy and a distinct cytokine development throughout pregnancy. The immunological dynamics in women with PCOS was significantly affected by maternal body mass index, smoking, and fetal sex.

CONCLUSION

Pregnancy in women with PCOS was associated with a strong early mobilization of inflammatory and other serum cytokines persisting throughout pregnancy, indicating a more activated immune status. These findings provide a novel basis for further study of PCOS and pregnancy complications.

Ultrasonographic placental thickness versus fetal outcome: A prospective study in Southern India

Background:

Variations in placental thickness are associated with increased perinatal morbidity and mortality. However, only very few studies have been established on the correlation between placental thickness with birth outcomes. This study correlated placental thickness in 2^nd and 3^rd trimesters with neonatal outcome, maternal weight gain, and body mass index (BMI).

Methods:

A total of 116 patients aged between 20 to 50 years with singleton pregnancy and regular menstrual history (and sure about their last menstrual period) were included. Placental thickness was measured at 24 and 36 weeks by ultrasound and was divided into three groups: Group A (normal placenta), Group B (thin placenta), and Group C (thick placenta); and correlated with neonatal outcome, maternal weight gain, and BMI.

Results:

Out of the 116 pregnant women, 55 (47.4%) were primigravida and 61 (52.6%) were multigravida. Six patients (3.6%) delivered pre-term before 36 weeks. In the 2^nd and 3^rd trimesters, most cases had normal placental thickness (Group A; 93.1% and 92.7%), followed by thin placenta (Group B; 5.2% and 7.3%) and thick placenta (Group C; 1.7% and 0), respectively. Two patients with thin placenta had neonatal death. A significant positive correlation was found between birth weight and placental thickness (at 24 weeks; 0.516^r, P<0.00001 and at 36 weeks; 0.669^r, P<0.00001) and maternal weight gain and birth weight (0.563^r, P<0.00001).

Conclusion:

Placental thickness on ultrasonography demonstrated well the correlation between birth weight in 2^nd and 3^rd trimesters and increased incidence of antenatal and postpartum complications resulting from thin placenta.

Cytokine Patterns in Maternal Serum From First Trimester to Term and Beyond

Pregnancy implies delicate immunological balance between two individuals, with constant changes and adaptions in response to maternal capacity and fetal demands. We performed cytokine profiling of 1149 longitudinal serum samples from 707 pregnant women to map immunological changes from first trimester to term and beyond. The serum levels of 22 cytokines and C-reactive protein (CRP) followed diverse but characteristic trajectories throughout pregnancy, consistent with staged immunological adaptions. Eotaxin showed a particularly robust decrease throughout pregnancy. A strong surge in cytokine levels developed when pregnancies progressed beyond term and the increase was amplified as labor approached. Maternal obesity, smoking and pregnancies with large fetuses showed sustained increase in distinct cytokines throughout pregnancy. Multiparous women had increased cytokine levels in the first trimester compared to nulliparous women with higher cytokine levels in the third trimester. Fetal sex affected first trimester cytokine levels with increased levels in pregnancies with a female fetus. These findings unravel important immunological dynamics of pregnancy, demonstrate how both maternal and fetal factors influence maternal systemic cytokines, and serve as a comprehensive reference for cytokine profiles in normal pregnancies.

The programming role of maternal antenatal inflammation on infants' early neurodevelopment: A review of human studies: Special Section on "Translational and Neuroscience Studies in Affective Disorders" Section Editor, Maria Nobile MD, PhD

BACKGROUND

Maternal inflammation during pregnancy is a frequently proposed mechanism underlying the link between maternal antenatal physical (e.g. infections, immune disease, obesity) and/or psychological (e.g. depression, anxiety) conditions and child outcomes. However, the extent to which maternal inflammation is directly associated with offspring's early development and health in humans remains largely unknown.

METHODS

In this review, empirical findings on the prospective association between maternal prenatal levels of inflammatory markers and infants' neurodevelopmental outcomes are summarized. Fifteen studies were included with sample sizes ranging from 36 to 6016 mother-infant dyads and average overall quality score 9.53 (range 6-12).

RESULTS

Findings concerning the link between maternal antenatal inflammation and, respectively, infants' health and birth outcomes, stress reactivity or cognitive development are mixed. However, it is noteworthy that all higher quality studies (scores >10) reviewed here do find evidence of an association between levels of inflammation, mostly as indexed by Interleukin-6 (IL-6), in healthy women across the whole gestation and offspring's neurodevelopmental outcomes, including structural and functional brain alterations.

LIMITATIONS

The correlational nature of the findings and conspicuous methodological heterogeneity across studies make drawing strong conclusions premature.

CONCLUSIONS

Findings, albeit preliminary, are consistent with animal studies and speak in favor of a role of maternal antenatal inflammation in shaping fetal development with possible long-term effects.

Mediating role of maternal serum interleukin-1beta and tumor necrosis factor-alpha in the association between environmental tobacco smoke exposure in pregnancy and low birth weight at term

OBJECTIVES

To explore the mediation effects of maternal serum interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) on the association between environmental tobacco smoke (ETS) exposure during pregnancy and low birth weight (LBW) at term.

METHODS

ETS exposure, birth weight, blood sample and covariates were collected from 195 pregnant women delivered term LBW infants and 195 controls delivered normal birth weight infants in two Maternity and Child Hospitals in Guangdong, China. Maternal serum IL-1β and TNF-α were measured by flow cytometry. Logistic regression models and path analyses explored the mediation effects of maternal IL-1β and TNF-α on the association between ETS exposure and LBW.

RESULTS

LBW was significantly associated with maternal ETS exposure (OR = 2.14 (95% CI =1.06-4.32)). TNF-α and IL-1β were significantly associated with both LBW (OR = 1.87 (1.41-2.47) and OR = 1.53 (1.14-2.05)) and ETS (β = 0.32 (0.04-0.60) and β = 0.27 (0.05-0.49)). Traditional mediation analyses indicated the separate mediation effect of TNF-α and IL-1β was 32.2% and 24.6%, respectively. Path analysis revealed the combined mediation effects of TNF-α and IL-1β as 29.4% in the pathway from ETS exposure to LBW.

CONCLUSIONS

Maternal serum IL-1β and TNF-α may play a mediating role in the association between maternal ETS exposure during pregnancy and term LBW.

Potential pathways by which maternal second-hand smoke exposure during pregnancy causes full-term low birth weight

It is well documented that maternal exposure to second-hand smoke (SHS) during pregnancy causes low birth weight (LBW), but its mechanism remains unknown. This study explored the potential pathways. We enrolled 195 pregnant women who delivered full-term LBW newborns, and 195 who delivered full-term normal birth weight newborns as the controls. After controlling for maternal age, education level, family income, pre-pregnant body mass index, newborn gender and gestational age, logistic regression analysis revealed that LBW was significantly and positively associated with maternal exposure to SHS during pregnancy, lower placental weight, TNF-α and IL-1β, and that SHS exposure was significantly associated with lower placental weight, TNF-α and IL-1β. Structural equation modelling identified two plausible pathways by which maternal exposure to SHS during pregnancy might cause LBW. First, SHS exposure induced the elevation of TNF-α, which might directly increase the risk of LBW by transmission across the placenta. Second, SHS exposure first increased maternal secretion of IL-1β and TNF-α, which then triggered the secretion of VCAM-1; both TNF-α and VCAM-1 were significantly associated with lower placental weight, thus increasing the risk of LBW. In conclusion, maternal exposure to SHS during pregnancy may lead to LBW through the potential pathways of maternal inflammation and lower placental weight.

Newborn body fat: associations with maternal metabolic state and placental size

BACKGROUND

Neonatal body composition has implications for the health of the newborn both in short and long term perspective. The objective of the current study was first to explore the association between maternal BMI and metabolic parameters associated with BMI and neonatal percentage body fat and to determine to which extent any associations were modified if adjusting for placental weight. Secondly, we examined the relations between maternal metabolic parameters associated with BMI and placental weight.

METHODS

The present work was performed in a subcohort (n = 207) of the STORK study, an observational, prospective study on the determinants of fetal growth and birthweight in healthy pregnancies at Oslo University Hospital, Norway. Fasting glucose, insulin, triglycerides, free fatty acids, HDL- and total cholesterol were measured at week 30-32. Newborn body composition was determined by Dual-Energy X-Ray Absorptiometry (DXA). Placenta was weighed at birth. Linear regression models were used with newborn fat percentage and placental weight as main outcomes.

RESULTS

Maternal BMI, fasting glucose and gestational age were independently associated with neonatal fat percentage. However, if placental weight was introduced as a covariate, only placental weight and gestational age remained significant. In the univariate model, the determinants of placenta weight included BMI, insulin, triglycerides, total- and HDL-cholesterol (negatively), gestational weight gain and parity. In the multivariable model, BMI, total cholesterol HDL-cholesterol, gestational weight gain and parity remained independent covariates.

CONCLUSION

Maternal BMI and fasting glucose were independently associated with newborn percentage fat. This effect disappeared by introducing placental weight as a covariate. Several metabolic factors associated with maternal BMI were associated with placental weight, but not with neonatal body fat. Our findings are consistent with a concept that the effects of maternal BMI and a number of BMI-related metabolic factors on fetal fat accretion to a significant extent act by modifying placental weight.

Adiposity-related inflammation: effects of pregnancy

In the nonpregnant population, there is extensive evidence of a systemic low-grade inflammatory status in relation to excess adipose tissue. Less is known about the relation during pregnancy.

OBJECTIVE

Our main objective was therefore to explore the effect of pregnancy on adiposity-related systemic inflammation.

DESIGN AND METHODS

This study is a longitudinal cohort study of 240 pregnant women of Scandinavian heritage at Oslo University hospital-Rikshospitalet, Norway from 2002 to 2005. The inflammatory markers (C-reactive protein [CRP], Interleukin-6 [IL-6], monocyte chemoattractant protein 1 [MCP-1], IL1-Ra, tumor necrosis factor receptor II, and IL-10) were measured at four timepoints during pregnancy and analyzed by enzyme immuno-assay. The women were categorized based on BMI at inclusion (BMI <25, 25-30, and >30 kg/m(2)). Data were analyzed by Friedman-test, Wilcoxon signed rank test, or Kruskal-Wallis test as appropriate.

RESULTS

Maternal adiposity was associated with significantly higher circulatory levels of several inflammatory markers (CRP, MCP-1, IL-6, and IL-1Ra). However, this proinflammatory upregulation was not evident toward the end of pregnancy, as levels of CRP, MCP-1, and IL-6 were not any longer significantly different between the BMI categories.

CONCLUSIONS

Although normal pregnancy exhibits proinflammatory features, this does not seem to have additive or synergistic effects on the inflammation associated with adiposity. On the contrary, we found that the BMI-dependent increase in proinflammatory markers was not evident at the end of pregnancy.

Fetal growth versus birthweight: the role of placenta versus other determinants

Introduction

Birthweight is used as an indicator of intrauterine growth, and determinants of birthweight are widely studied. Less is known about determinants of deviating patterns of growth in utero. We aimed to study the effects of maternal characteristics on both birthweight and fetal growth in third trimester and introduce placental weight as a possible determinant of both birthweight and fetal growth in third trimester.

Methods

The STORK study is a prospective cohort study including 1031 healthy pregnant women of Scandinavian heritage with singleton pregnancies. Maternal determinants (age, parity, body mass index (BMI), gestational weight gain and fasting plasma glucose) of birthweight and fetal growth estimated by biometric ultrasound measures were explored by linear regression models. Two models were fitted, one with only maternal characteristics and one which included placental weight.

Results

Placental weight was a significant determinant of birthweight. Parity, BMI, weight gain and fasting glucose remained significant when adjusted for placental weight. Introducing placental weight as a covariate reduced the effect estimate of the other variables in the model by 62% for BMI, 40% for weight gain, 33% for glucose and 22% for parity. Determinants of fetal growth were parity, BMI and weight gain, but not fasting glucose. Placental weight was significant as an independent variable. Parity, BMI and weight gain remained significant when adjusted for placental weight. Introducing placental weight reduced the effect of BMI on fetal growth by 23%, weight gain by 14% and parity by 17%.

Conclusion

In conclusion, we find that placental weight is an important determinant of both birthweight and fetal growth. Our findings indicate that placental weight markedly modifies the effect of maternal determinants of both birthweight and fetal growth. The differential effect of third trimester glucose on birthweight and growth parameters illustrates that birthweight and fetal growth are not identical entities.