Objective: To study the association between mode of conception and risk of preterm birth (PTB), including, spontaneous and provide-initiated PTB. Design: Retrospective cohort study Setting and Population: Population-based cohort included all singleton livebirths and stillbirth in Ontario, Canada, 2006-2014. Methods: Mode of conception comprised (i) subfertility without infertility treatment (N = 68,822); (ii) non-invasive infertility treatment (ovulation induction +/- intrauterine insemination) (N = 9024); or (iii) Invasive infertility treatment (in vitro fertilization [N = 8038) – each compared to births by unassisted conception (N = 646,926). Modified Poisson regression generated risk ratios (RR). Confounding was handled by inverse probability of treatment weighting using a propensity that included maternal demographics and pre-existing conditions. Main Outcome Measure: PTB < 37 completed weeks’ gestation. PTB was further categorized as spontaneous PTB or provider-initiated PTB. Results: PTB occurred among 6.0% of births by unassisted conception, 7.7% with subfertility, 8.0% with non-invasive infertility treatment, and 10.8% following invasive infertility treatment. The RR of provider-initiated PTB was higher in women with subfertility (RR 1.23, 95% CI 1.16-1.31), non-invasive infertility treatment (RR 1.48, 1.29-1.69) and invasive infertility treatment (RR 2.35, 2.09-2.64) – each relative to births by unassisted conception. The corresponding RR for spontaneous PTB were 1.15 (95% CI 1.10-1.19), 1.19 (95% CI 1.09-1.31) and 1.40 (95% CI 1.27-1.53). Conclusions: Subfertility, and receipt of infertility treatment, are each associated with a higher risk of PTB, especially provider-initiated PTB. Strategies are needed to reduce the underlying indications to deliver these women before term.

Objective: To improve the prediction of maternal end-organ injury or death using routinely-collected variables from the pre-pregnancy and the early pregnancy period. Design: Population-based cohort study using linked administrative health data. Setting: Ontario, Canada, April 1, 2006 to March 31, 2014. Sample: Women aged 18-60 years with a livebirth or stillbirth, of which one birth was randomly selected per woman. Methods and main outcome measures: We constructed a CPM for the primary composite outcome of any maternal end-organ injury or death, arising between 20 weeks’ gestation and 42 days after the birth hospital discharge date. Our CPM included variables collected from 12 months before estimated conception until 19 weeks’ gestation. We developed a separate CPM for parous women to allow for the inclusion of factors from previous pregnancy(ies). Results: Of 634,290 women, 1969 experienced the primary composite outcome (3.1 per 1000). Predictive factors in the main CPM included maternal world region of origin, chronic medical conditions, parity, and obstetrical/perinatal issues – with moderate model discrimination (C-statistic 0.68, 95% CI 0.66-0.69). Among 333,435 parous women, the C-statistic was 0.71 (0.69-0.73) in the model using variables from the current (index) pregnancy as well as pre-pregnancy predictors and variables from any previous pregnancy. Conclusions: A combination of factors ascertained early in pregnancy through a basic medical history help to identify women at risk for severe morbidity, who may benefit from targeted preventive and surveillance strategies including appropriate specialty-based antenatal care pathways. Further refinement of this model would enable clinical use.