The multiple pregnancy rate increased by 50% in Norway during the time period 1988-2004, even when twin pregnancies from assisted reproduction were excluded. Maternal age and assisted reproductive technologies cannot alone satisfactorily explain the rise in the twinning rate in Norway.
Objective To examine the risk of pre-eclampsia (PE) in women conceiving after assisted reproductive technologies (ART). Potential confounding from maternal age, long intervals between births, new partner and smoking were evaluated.Design and setting Population-based cohort study with data from the Medical Birth Registry of Norway. Methods Births to the same mother were linked in sibship data files with information of ART.Main outcome measures Odds ratio (OR) (95% confidence intervals) of PE in pregnancies conceived by ART compared with spontaneous conception, stratified by parity.Results The prevalence of PE was 5.1% in first, 2.2% in second and 2.1% in third pregnancies. Corresponding figures in ART pregnancies were 6.0%, 3.3% and 4.4%. Hence, the odds ratios of PE in ART pregnancies relative to spontaneous pregnancies increased from 1.2 (1.1-1.3) in first, 1.5 (1.3-1.8) in second to 2.1 (1.4-3.3) in third pregnancies. Adjusting by maternal age lowered the odds ratio to 1.3 (1.1-1.6) and 1.8 (1.2-2.8) in second and third pregnancies, respectively. Multi-adjusted, birth interval had more impact than change of partner. Smoking was associated with a strongly reduced PE risk (odds ratio 0.65; 0.62-0.69), but there was no confounding by smoking on the ART associated risk.Conclusions Assisted reproductive technologies increases the risk of PE, and the risk may increase by parity. The association between ART pregnancies and PE is to some extent explained by interbirth intervals and advanced maternal age, but not to change of partner or smoking.
The association between preconceptional folate use and twin pregnancies was strongly confounded by IVF. After accounting for IVF pregnancies and underreporting, we found no evidence for an association between preconceptional folate supplements and twinning.
Placenta needed to be removed manually in 0.60% of all deliveries in our department. It was associated with increased incidence of hemorrhage and consequently low hemoglobin values. Women with a history of retained placenta have an increased risk of recurrence of retained placenta in subsequent deliveries.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.