As a first step, rates of adverse outcomes per 1000 live births were calculated according to infant sex, GA, and the studied period. Thereafter, for each time period, using the gestational age categories as the exposure variable (early term and late preterm infants, respectively, with midterm infants as the reference category), we used logistic regression to estimate odds for prematurity-related adverse outcomes such as neonatal death, low Apgar score (<7 at 5 min), pneumothorax, RDS, other respiratory conditions, and hyperbilirubinemia. Then, for each time period, odds ratios (ORs) with 95 % confidence intervals (CIs) for adverse prematurity-related outcomes among male infants, always in relation to their female counterparts, were calculated with logistic regression, separately for early term and for late preterm infants. Finally, to estimate the change in male risk before and after the introduction of ultrasound pregnancy dating, the relative change in odds for adverse prematurity-related outcomes between the two periods, among male infants in the early term and late preterm groups in relation to their female counterparts, was calculated as the ratio between the ORs for each period (Cohort Ratio, CR). The multivariate analyses were adjusted for maternal age, parity, and level of hospital care.
This new statistical analyses was indeed conducted by using the SAS nine.step 3 software program (SAS Institute, Cary, NC, USA). The ORs and CRs with regards to 95 % count on periods have been projected on GENMOD techniques.
Performance
The features of the study cohorts was displayed within the Table step one , with the quantity of male and female kids born inside the for every single GA classification throughout the 1973–1978 and you can 1995–2010. The brand new ratio away from midterm births (74.6 % in early compared to. 70.5 % throughout the later several months) are large in the early cohort, and the proportion of early term births (21.0 % in the early against. twenty-five.5 % throughout the late period) are reduced in the early cohort. The newest proportion lately preterm births try comparable on the a couple of cohorts (cuatro.3 % in the early vs. 4.0 % throughout the later months). Imply maternal many years the very first time several months (1973–1978) are twenty seven decades (SD = 5), and you will imply maternal many years on the later time frame (1995–2010) was 29 (SD = 5).
Table step one
Number and you will delivery out of one or two cohorts off singleton births when you look at the Sweden, with imply and you may important deviation (SD) regarding birthweight, delivery duration, and you can Apgar get by the infant sex and you will gestational years, both before and after new utilization of ultrasound for maternity relationship
Table dos shows rates out of prematurity-relevant bad consequences because of the gender and you can gestational ages on one or two schedules. The new ORs to own adverse outcomes was given midterm infants out-of an identical intercourse given that source category. Costs off bad neonatal consequences have been generally straight down for male and lady children regarding the after months. Cost of bad outcomes have been lower getting ladies kids than for male infants, in time periods, apart from neonatal death certainly one of late preterm babies into the new later months. ORs for prematurity-relevant consequences have been straight down having early name infants, compared to late preterm infants, as expected.
Table 2
Costs and adjusted a odds rates (OR) that have 95 % rely on durations (95 % CI) for prematurity-associated unfavorable effects from the gestational many years (GA) at the beginning certainly one of infants born in the thirty five–36 weeks or 37–38 days, compared with 39–forty days, pre and post brand new implementation of ultrasound into the Sweden to possess maternity relationship
Table step 3 boasts the latest ORs to possess prematurity-related negative effects certainly one of early title men children, that have girls kids just like the reference category, regarding two-time episodes. ORs for negative outcomes have been high for all comparisons inside relatives so you’re able to people infantsparing both schedules, ORs having male kids was indeed improved on the 2nd study period, since reflected by mathematically high cohort rates (CR). Between them schedules, discover a boost in potential for early name men kids, when considering ladies, to own pneumothorax (CR 2.05, CI step 1.step 33–step 3.16), RDS (CR step 1.99, CI 1.33–2.98), a low Apgar rating (CR step 1.26, CI step 1.08–step one.47), most other breathing conditions (CR 1.14, CI 1.00–step 1.30), and you will hyperbilirubinemia (CR step one.12, CI step 1.06–step one.19) on afterwards time period. There is no high improvement in cohort ratios to possess perinatal death (Table step three ).