Maternal smoking during pregnancy and fetal growth. Effects in preterm infants of gestational age less than 33 weeks.

OBJECTIVE: To evaluate the effects of maternal smoking during pregnancy on foetal growth in preterm infants with gestational age (GA) <33 weeks. POPULATION AND METHODS: Prospective observational cross-sectional study from two French perinatal networks cohort of preterm infants. Cases were 358 very preterm infants (GA 24-32 weeks) divided into two groups as maternal smokers (129) and non-smokers (229). 361 term infants (GA 37-41 weeks) also divided into two groups as maternal smokers (129) and non-smokers (232) served as comparison group (controls). We studied the influence of maternal smoking on foetal anthropometric growth parameters (BW, BL and head circumference defined according to AUDIPOG curves) in groups and compared cases and controls. Other causes of foetal growth restriction were excluded. RESULTS: Maternal characteristics (age, height, pre-pregnancy body weight, parity, foetus sex) were similar in both groups and sub-groups. Mothers who smoked were younger (P <0.001), more likely to be unemployed (P <0.001) and to have undergone less school education (P <0.001). Smoking did not alter foetal growth in preterm infants: maternal smokers versus non-smokers BW (P = 0.52), BL (P = 0.44) and HC (P = 0.81). Growth restriction was marked in term infants with BW (P <0.001), BL (P <0.001) and HC (P <0.01). In multivariate analysis, after adjustment for other confounding factors, foetal growth appeared to be significantly altered by maternal smoking during pregnancy only in term infants. CONCLUSION: Our study suggests that effects of maternal smoking during pregnancy on foetal growth are gestational age-dependent.

Very preterm birth: who has access to antenatal corticosteroid therapy?

We describe the administration of antenatal corticosteroid therapy (ACT) for liveborn very preterm neonates in a population-based study. A total of 790 very preterm neonates (between 24 and 31 full weeks of gestation) were included in this regionally defined population of very preterm neonates in France. The main outcome measure was non-access to ACT. Data were analysed using logistic and polytomous models to control for neonatal and sociodemographic characteristics, mechanisms of very preterm birth and neonatal network organisation. As compared with level III, births in levels I-II maternity units were closely related to non-access to ACT (60.1% vs. 8.8%), but not to pregnancy follow-up (19.7% vs. 17.8%). Only 6.3% of very preterm neonates that benefited from antepartum referral did nor receive ACT. Births associated with rupture of membranes and gestational hypertension were significantly more often transferred to level-III units (73.8% and 68.3% respectively) than those due to maternal bleeding and spontaneous labour (57.0% and 50.7% respectively), and the neonates had a lower probability of not receiving ACT (8.5%, 11.5%, 23.0%, 31.2% respectively). Very preterm neonates referred in utero to a level-III unit came from a more favourable socio-economic environment. Non-access to ACT was more often observed in neonates born to 14- to 24-year-old mothers, smokers, of low socio-economic status, and preterm birth resulting from maternal bleeding or spontaneous labour. These data from a French regional study show that access to ACT is not only explained by practitioners' support of recommendations. In our population-based study, ACT access was related to socio-economic factors and to the mechanisms of very preterm birth. Improving the rate of access to ACT should take these organisational, medical and socio-economic dimensions into account.

Heart rate variability in preterm infants and maternal smoking during pregnancy.

OBJECTIVE: Tobacco smoke exposure increases the risk of premature birth and of dying of sudden infant death syndrome (SIDS). Prematurity significantly increases the risk of dying of SIDS, but mechanisms underlying this epidemiological finding are unclear. The cumulated effect of both prematurity and prenatal exposure to nicotine on autonomic heart rate control has not been studied. METHODS: Using coarse-graining spectral analysis, we compared heart rate variability (HRV) indices of preterm newborns at 33-34 weeks post-conceptional age from smoking (n = 19) and non-smoking (n = 21) mothers. Assessment of tobacco exposure relied on maternal reports and newborns cotinine analysis. We observed how indicators of HRV depended on gestational age at birth. RESULTS: At 33-34 weeks postconceptional age, the newborns from smoking mothers had lower HRV low frequency power normalised to the total spectral power (LF/TP) than the control group (median values: 8% vs. 15% respectively, p < 0.02). In the non-smoking group, RR-interval values and total HRV power were correlated with gestational age at birth, with a shorter RR and a lower total HRV power in lesser gestational ages (rho = 0.67, p = 0.03, rho = 0.71, p = 0.003 respectively). This correlation was not observed for RR values in the group with smoking mothers.