BACKGROUND: Prenatal exposure to opioids (PEO) is a worldwide public health issue. Opioids cross the placental barrier and may affect the developing foetus and the birth outcomes.
OBJECTIVE: This review aimed to explore newborns\' weight, length and head circumference, preterm birth, and perinatal death as primary outcomes in relation to PEO. The secondary outcomes were gestational age at birth, Apgar scores and length of hospitalisation after delivery.
METHODS: PubMed, Embase, PsycInfo and the Web of Science.
METHODS: Inclusion criteria were (i) cohort, case-control or cross-sectional peer-reviewed studies published in English through 1 March 2021; (ii) comparing outcomes between prenatal exposed and unexposed groups to opioids (prescribed or obtained illegally). Exclusion criteria were foetal alcohol syndrome and non-opioid primary exposure.
RESULTS: Data were extracted by two authors. The Newcastle-Ottawa Quality Assessment Scale was used for study quality assessment. Due to heterogeneity across studies, we used random effects models to obtain pooled standardised mean difference (SMD), pooled risk ratio (RR) and 95% confidence interval (CI).
RESULTS: Data from 80 studies were extracted. In meta-analyses, opioid-exposed neonates had lower birthweight (SMD -0.77, 95% CI -0.90, -0.64, I2  = 82%), smaller head circumference (SMD -0.67, 95% CI -0.86, -0.48, I2  = 84%), shorter birth length (SMD -0.97, 95% CI -1.24, -0.70, I2  = 91%) and gestational age (SMD -0.45, 95% CI -0.60, -0.30, I2  = 80%) than unexposed neonates. Pooled risks of neonatal death and preterm birth were higher among opioid-exposed compared to unexposed neonates (RR 4.05, 95% CI 2.12, 7.72, I2  = 73%; and RR 1.92, 95% CI 1.57, 2.35, I2  = 99%).
CONCLUSIONS: We found increased risks of adverse birth outcomes in relation to PEO. Caution should be used in interpreting the findings, as many studies were rated as poor quality, and with substantial inter-study heterogeneity. Future studies should ensure comparability of opioid-exposed and -unexposed group to strengthen internal validity.

The aetiology of primary central nervous system (CNS) tumours remains largely unknown, but their childhood peak points to perinatal parameters as tentative risk factors. In this meta-analysis, we opted to quantitatively synthesise published evidence on the association between birth anthropometrics and risk of primary CNS tumour.
Eligible studies were identified via systematic literature review; random-effects meta-analyses were conducted for the effect of birth weight and size-for-gestational-age on childhood and adult primary CNS tumours; subgroup, sensitivity, meta-regression and dose-response by birth weight category analyses were also performed.
Forty-one articles, encompassing 53,167 CNS tumour cases, were eligible. Birth weight >4000 g was associated with increased risk of childhood CNS tumour (OR: 1.14, [1.08-1.20]; 22,330 cases). The risk was higher for astrocytoma (OR: 1.22, [1.13-1.31]; 7456 cases) and embryonal tumour (OR: 1.16, [1.04-1.29]; 3574 cases) and non-significant for ependymoma (OR: 1.12, [0.94-1.34]; 1374 cases). Increased odds for a CNS tumour were also noted among large-for-gestational-age children (OR: 1.12, [1.03-1.22]; 10,339 cases), whereas insufficient data for synthesis were identified for other birth anthropometrics. The findings remained robust across subgroup and sensitivity analyses controlling for several sources of bias, whereas no significant heterogeneity or publication bias were documented. The limited available evidence on adults (4 studies) did not reveal significant associations between increasing birth weight (500-g increment) and overall risk CNS tumour (OR: 0.99, [0.98-1.00]; 1091 cases) or glioma (OR: 1.03, [0.98-1.07]; 2052 cases).
This meta-analysis confirms a sizeable association of high birth weight, with childhood CNS tumour risk, particularly astrocytoma and embryonal tumour, which seems to be independent of gestational age. Further research is needed to explore underlying mechanisms, especially modifiable determinants of infant macrosomia, such as gestational diabetes.

BACKGROUND: Previous studies suggest that birth weight is related to later risk of asthma. However, few meta-analyses have investigated these associations. Therefore, we performed a meta-analysis with different classifications to further validate the relationship between birth weight and asthma.
METHODS: PubMed (1990-2013), ScienceDirect (1990-2013), EMBASE(1990-2013),EBSCO (1990-2013) and Springer (1990-2013) were searched for articles. The following MeSH terms were used: \"birth weight\", \"fetal growth retardation\", \"intrauterine growth restriction\", \"asthma\", \"wheezing\".
RESULTS: We included 18 studies with data from a total of over 90,000 children and adults. (1) Low birth weight (<2,500g) as compared with BW>2,500g and BW=2500-4000g was associated with increased risk of asthma (Children: OR, 1.28; 95% CI, 1.09-1.50, P<0.05; OR, 1.34; 95% CI, 1.13-1.60, P<0.05, Adults: OR, 1.25; 95% CI, 1.12-1.39, P<0.05; OR, 1.25; 95% CI, 1.12-1.40, P<0.05). (2) High birth weight (>4,000g) was not associated with the risk of asthma when BW<4,000g and BW=2500-4000g were used as the reference.
CONCLUSIONS: These results suggest that low birth weight (<2,500g) is associated with increased risk of asthma both in children and adults and may serve as a mediator between prenatal influences and later disease risk; but high birth weight (>4,000g) was not associated with increased risk of asthma.