Lastly, as airway development occurs in the first trimester, we tested the interactions between maternal 25(OH D concentration and the trimester of blood sample (categorized as a binary variable indicating 1st trimester) in models of pulmonary function.
Maternal urine samples were obtained, mostly during the third trimester: 25% of samples were collected between 25 and 30 gestational weeks, 45% between 31 and 35 weeks, and the remainder between 36 and 40 weeks.
Despite the overall interspersed pattern of clustering of first trimester samples of various gestations (8 - 12 weeks), we tested to see whether any genomic regions undergo selective changes in methylation during the transition from early first trimester to late first/early second trimester.
Stool samples to measure geohelminth infections have been collected from mothers in the third trimester of pregnancy (stool samples collected after birth and before the child is 14 days old are considered to represent a third trimester stool sample where the mother has not received anthelmintic treatment) and from infants at 3, 7, 13, 18, 24, and 30 months, and at 3, 5, and 8 years.
For example, we previously reported median RBC folate concentrations ≥ 3000 nmol/L during the 3rd trimester of pregnancy in a sample of well-educated Canadian women [ 15].
Acute enterovirus infections were diagnosed by increases in enterovirus IgG and IgM in samples taken from the mother at the end of the first trimester of pregnancy and cord blood samples taken at delivery.
Table 3 shows results of the regression analyses of the association between birth outcomes and the organophosphate insecticides chlorpyrifos and diazinon in a) personal air samples collected from the mother over 48 hr during the third trimester of pregnancy and b) blood samples collected from the newborn at delivery.
Indeed, very recent screening studies of first-trimester samples of large cohorts of uncomplicated and pathological pregnancies revealed detection rates for developing early and late PE of 90% and 60%, respectively, when maternal factors, biophysical and biochemical markers were combined [23,32].
Figure 1a shows the distribution of maternal exposure levels to background pollutants three months before pregnancy and during each trimester of pregnancy in the total sample of 370 mothers.
