Obstetrical characteristics and neonatal outcome according to aetiology of preterm birth: a cohort study

The aetiology of preterm birth and risks of cerebral palsy and cognitive impairment: A systematic review and meta-analysis

AIM

The associations between the aetiology of preterm birth and later neurodevelopmental outcomes are unclear. A systematic review and meta-analysis examined the existing evidence.

METHODS

The PubMed and Embase databases were searched for papers published in English from inception to 16 December 2020. We included original papers on the causes of preterm birth and the risks of cerebral palsy (CP) and suboptimal cognitive development. Two reviewers independently evaluated the studies and extracted the data.

RESULTS

The literature search yielded 5472 papers and 13 were selected. The aetiology of preterm birth was classified under spontaneous or medically indicated delivery. A meta-analysis was performed, comprising 104 902 preterm infants from 11 papers on CP. Preterm infants born after a medically indicated delivery had a lower CP risk than infants born after spontaneous delivery, with a pooled odds ratio of 0.59 (95% confidence interval 0.40-0.86). This result was robust in the subgroup and sensitivity analyses. Cognitive development was reported in three papers, which suggested that worse outcomes were associated with medically indicated deliveries.

CONCLUSION

The aetiology of preterm delivery may contribute to the risk of CP and cognitive delay. Further research is needed, using individual-level meta-analyses to adjust for possible confounders, notably gestational age.

Extreme Temperature Exposure and Risks of Preterm Birth Subtypes Based on a Nationwide Survey in China

BACKGROUND

Previous studies have reported that ambient temperature may affect perinatal outcomes. However, whether extreme temperature affects the risk of preterm birth (PTB) remains controversial. Studies on the associations of extreme temperature with PTB subtypes are lacking.

OBJECTIVES

We aimed to investigate the associations of extreme climate events with the risks of PTB and its subtypes, discerning possible modifiers.

METHODS

Data on all singleton deliveries were obtained from the China Labor and Delivery Survey (CLDS), a nationwide investigation implemented in 2015 and 2016. PTB was defined as gestational weeks < 37 and then categorized as early (24-34 wk) and late PTBs (35-36 wk), and clinical subtypes [spontaneous PTB, preterm premature rupture of the fetal membranes (PPROM), iatrogenic PTB]. Ambient temperature data were provided by the China National Weather Data Sharing System. Five heat indexes and five cold indexes were used to define heat waves and cold spells. Generalized linear mixed models with a random term by hospital unit were used to assess the associations of short-term prenatal extreme temperature exposure. The Cox proportional hazard regression model was applied to assess the nonlinear associations of low- or high-temperature exposure at the whole and different trimesters of pregnancy with the risk of PTB. Stratified analyses were conducted to assess the possible modification by geographic region and fetal sex.

RESULTS

A total of 70,818 singleton births from 96 hospitals in China were included, among which 4,965 (7.01%) were PTBs. Exposure to extreme cold events 1 wk before delivery was associated with an increased PTB risk, with an adjusted odds ratio (aOR) [95% confidence intervals (CIs)] of 1.07 (95% CI: 1.04, 1.10) and 1.06 (1.04, 1.09) for the total days when the daily average temperature below the fifth percentile (fifth-days) and the 10th percentile (10th-days), 1.18 (1.04, 1.34) for the cold spells when the daily average temperature below the fifth percentile for two consecutive days (fifth-2D), 1.09 (1.03, 1.16) and 1.12 (1.06, 1.19) for the cold spells when the daily average temperature below the 10th percentile for three and two consecutive days (10th-3D and 10th-2D), respectively. Results of extreme temperature exposure during 2 weeks before delivery showed similarly significant associations. The association between cold spells and PTB tended to be stronger for late PTB than for early PTB. Cold spells were mainly associated with spontaneous PTB and late PPROM. A stratified analysis indicated that pregnant women in western and northern regions tended to be more sensitive to cold spells, and pregnant women with a female fetus appeared to be at a higher risk of PTB when exposed to cold spells. Pregnant women in late pregnancy were more susceptible to extreme temperatures. No significant or stable association was found between heat waves and preterm birth.

DISCUSSION

Exposure to cold spells was associated with an increased risk of PTB, especially late, spontaneous PTB and PPROM. The associations appeared to be more pronounced in the north and west regions and in pregnancies with female fetuses. https://doi.org/10.1289/EHP10831.

Exposure of ambient PM2.5 during gametogenesis period affects the birth outcome: Results from the project ELEFANT

Various environmental and behavioural factors influence neonatal health. Gamete formation (gametogenesis) is a crucial period which affects embryo development and neonatal health and ambient air pollution exposure at this stage may lead to an adverse birth outcome. Previous epidemiological and toxicological research demonstrated a strong association between maternal ambient air pollution exposure and adverse birth outcomes. However, the joint exposure-outcome of paternal exposure (76 days before the last menstruation and 14 days after the last menstruation) and maternal exposure (14 days after the last menstruation) when exploring the mechanism of the influence of air pollutants on pregnancy outcome and neonatal health remains unexplored. Here, in the Project Environmental and LifEstyle FActors iN metabolic health throughout life-course Trajectories (ELEFANT), we collected the data of 10,960 singleton pregnant women with 24-42 completed gestational weeks and included them in this study. A multinominal logistic regression model was applied to investigate the association between adverse birth outcomes and ambient PM_2.5 exposure levels during spermatogenesis and oogenesis. Results from the binary classification of ambient PM_2.5 exposure showed that the risk of abnormal birthweight was significantly greater when ambient PM_2.5 exposure was both higher during spermatogenesis and oogenesis, with RRs of 1.86 (95% CI: 1.02, 3.39). The risk of macrosomia (RR: 1.88 (95% CI: 1.13, 3.12)) increased significantly when ambient PM_2.5 levels were higher during spermatogenesis. Primiparity and primigravity are more likely to be influenced by higher ambient PM_2.5 levels during spermatogenesis. In conclusion, more attention should be paid to higher exposure level of ambient PM_2.5 during spermatogenesis.

Extracellular DNA levels and cytokine profiles in preterm birth: a cohort study

PURPOSE

The content of eight different cytokines, cell-free DNA (cfDNA) and cell-free fetal DNA (cffDNA) in women's plasma during preterm birth (PB) was studied. The purpose of this study was to identify the relationships between the investigated factors and determine their prognostic significance.

METHODS

Venous blood samples were collected from 45 women with PB and 35 women with full-term labor at 22-31 and 32-36 weeks of gestation, as well as from 17 women during labor at 39-40 weeks of gestation. The concentration of IL-2, IL-4, IL-6, IL-8, IL-10, GM-CSF, IFN-γ and TNF-α cytokines in peripheral blood plasma was measured by multiplex method. The level of cfDNA and cffDNA was evaluated using PCR analysis.

RESULTS

It was found that, the level of IL-6, IL-8 and cfDNA in the blood was significantly increased in women with PB at 22-31 weeks of gestation (p = 0.044, p = 0.001, p < 0.001) and 32-36 weeks of gestation (p = 0.025, p = 0.001, p = 0.002) compared to women with physiological pregnancy at the same terms. The level of cffDNA (p = 0.014) was significantly increased in women with PB at 32-36 weeks of gestation. The IL-8 content had a significant correlation with the cfDNA level in women with PB at all stages of labor and with the cffDNA level in the group who gave birth at 32-36 weeks of gestation. There was no correlation between IL-8, cfDNA and cffDNA, but there was consistency with other cytokines at all studied terms and during delivery in the term-delivery group.

CONCLUSION

The results of the study suggest that cfDNA is a potential marker of PB and show that the aberrant relationship between cfDNA and IL-8 may be important in the genesis of PB.

Sex Differences Are Here to Stay: Relevance to Prenatal Care

Sex differences exist in the incidence and presentation of many pregnancy complications, including but not limited to pregnancy loss, spontaneous preterm birth, and fetal growth restriction. Sex differences arise very early in development due to differential gene expression from the X and Y chromosomes, and later may also be influenced by the action of gonadal steroid hormones. Though offspring sex is not considered in most prenatal diagnostic or therapeutic strategies currently in use, it may be beneficial to consider sex differences and the associated mechanisms underlying pregnancy complications. This review will cover (i) the prevalence and presentation of sex differences that occur in perinatal complications, particularly with a focus on the placenta; (ii) possible mechanisms underlying the development of sex differences in placental function and pregnancy phenotypes; and (iii) knowledge gaps that should be addressed in the development of diagnostic or risk prediction tools for such complications, with an emphasis on those for which it would be important to consider sex.

Use of the Arabin pessary in women at high risk for preterm birth: long-term experience at a single tertiary center in Malaysia

Background

Spontaneous preterm birth is a global issue that contributed to perinatal morbidities and mortalities worldwide. The study aimed to describe the experience at UKM Medical Center in managing women at high risk for spontaneous preterm birth using the Arabin pessary.

Methods

This is a retrospective observational study involving 58 pregnancies from 1st January 2013 to 31st December 2019. Inclusion criteria were previous mid-trimester miscarriage and/or preterm birth, previous cervical surgery or short cervical length on routine sonogram. The demographic data, characteristics of each pregnancy and details of outcomes and management were described.

Results

The majority of women were Malay with mean age and body mass index of 32.9 ± 4.2 years and 27.1 ± 6.3 kg/m² respectively. The most frequent indications for Arabin pessary insertion were previous mid-trimester miscarriage (46.4%) and early preterm birth (17.2%). A total of 73.4% of these women had the pessary inserted electively at a mean cervical length of 31.6 ± 9.1 mm at median gestation of 15.0 weeks. They were managed as outpatient (56.9%), inpatient (24.1%) or mixed (19.0%) with combination of progestogen (81.0%) and 53.4% received antenatal corticosteroids. Spontaneous preterm birth at or more than 34 weeks gestation occurred in 74.1% with birthweight at or more than 2000 g (82.4%). Despite cervical funneling in 12 women (20.7%), 66.7% delivered at or later than 34 weeks gestation and 2 (16.7%) resulted in miscarriage.

Conclusions

Insertion of the Arabin pessary is beneficial to prevent spontaneous preterm birth in pregnant women who are at high risk. In particular, early insertion and close monitoring allows the best possible outcomes.

Trial registration

This study was retrospectively registered with ClinicalTrials.gov (NCT04638023) on 20/11/2020.

Iatrogenic vs. Spontaneous Preterm Birth: A Retrospective Study of Neonatal Outcome Among Very Preterm Infants

Objective: Preterm birth is a leading contributor to childhood morbidity and mortality, and the incidence tends to increase and is higher in developing countries. The aim of this study was to analyze the potential impact of preterm birth in different etiology groups on neonatal complications and outcomes and to gain insight into preventive strategies.

Methods: We performed a retrospective cohort study of preterm infants less than 32 weeks' gestation in the Third Affiliated Hospital of Zhengzhou University from 2014 to 2019. Preterm births were categorized as spontaneous or iatrogenic, and these groups were compared for maternal and neonatal characteristics, neonatal complications, and outcomes. All infants surviving at discharge were followed up at 12 months of corrected age to compare the neurodevelopmental outcomes.

Results: A total of 1,415 mothers and 1,689 neonates were included, and the preterm population consisted of 1,038 spontaneous preterm infants and 651 iatrogenic preterm infants. There was a significant difference in the incidence of small for gestational age between the two groups. Infants born following spontaneous labor presented with a higher risk of intraventricular hemorrhage, whereas iatrogenic preterm birth was associated with higher risk of necrotizing enterocolitis and coagulopathy and higher risk of pathoglycemia. There was no difference in mortality between the two groups. Follow-up data were available for 1,114 infants, and no differences in neurologic outcomes were observed between the two preterm birth subtypes.

Conclusions: Preterm births with different etiologies were associated with some neonatal complications, but not with neurodevelopmental outcomes at 12 months of corrected age.