Objectives To assess the cumulative costs and consequences of double embryo transfer (DET) or elective single embryo transfer (eSET) in women commencing in vitro fertilisation (IVF) treatment aged 32, 36 and 39 years. Design Microsimulation model.Setting Three assisted reproduction centres in Scotland.Sample A total of 6153 women undergoing treatment at one of three Scottish IVF clinics, between January 1997 and June 2007.Methods A microsimulation model, populated using data inputs derived from a large clinical data set and published literature, was developed to compare the costs and consequences of using eSET or DET over multiple treatment cycles.Main outcome measures Disability-free live births; twin pregnancy rate; women's quality-adjusted life-years (QALYs); health service costs.Results Not only did DET produce a higher cumulative live birth rate compared with eSET for women of all three ages, but also a higher twin pregnancy rate. Compared with eSET, DET ranged from costing an additional £27 356 per extra live birth in women commencing treatment aged 32 years, to costing £15 539 per extra live birth in 39-year-old women. DET cost £28 300 and £20 300 per additional QALY in women commencing treatment aged 32 and 39 years, respectively.Conclusions Considering the high twin pregnancy rate associated with DET, coupled with uncertainty surrounding QALY gains, eSET is likely to be the preferred option for most women aged £36 years. The cost-effectiveness of DET improves with age, and may be considered cost-effective in some groups of older women. The decision may best be considered on a case-by-case basis for women aged 37-39 years.Keywords Cost-effectiveness, in vitro fertilisation, single embryo transfer.Please cite this paper as: Scotland G, McLernon D, Kurinczuk J, McNamee P, Harrild K, Lyall H, Rajkhowa M, Hamilton M, Bhattacharya S. Minimising twins in in vitro fertilisation: a modelling study assessing the costs, consequences and cost-utility of elective single versus double embryo transfer over a 20-year time horizon.

Aim To determine the effect of maternal body mass index (BMI) on obstetric and perinatal outcomes in all pregnancies at a population level in Scotland. Methods All women with singleton pregnancies who delivered in Scottish maternity units from 01/01/2003 until 31/12/2009 were included (124,280 deliveries from 109,592 women). Women were grouped by WHO BMI criteria with BMI 18.5<25kg/m2 used as the reference group. Data were analysed by univariate tests and random effects hierarchical regression. A fixed effects model was used for sensitivity analyses. Odds ratios (OR) were adjusted for maternal age, deprivation and smoking. Results Overweight, obese and morbidly obese women respectively were at an increased risk of essential hypertension (adjusted OR 1.87, 95% confidence interval (CI)1.18-2.97, 11.90 (7.18-19.72) and 36.10 (18.33-71.10)), pregnancy induced hypertension (1.76 (1.6-1.95), 2.98 (2.65-3.36) and 4.48 (3.57-5.63)), pre-existing diabetes (2.54 (1.79-3.61), 3.76 (2.59-5.47), 7.71 (4.04-14.71)), gestational diabetes (3.39 (2.30-4.99), 11.90 (7.54-18.79), 67.40 (37.84-120.03)), induction of labour (IOL) (1.30 (1.25-1.35), 1.64 (1.57-1.72), 1.97 (1.78-2.18)), elective caesarean section (CS) (2.06 (1.84-2.30), 4.61 (4.06-5.24) 17.92 (13.20-24.34) or emergency CS (1.94 (1.71-2.21), 3.40 (2.91-3.96) 14.34 (9.38-21.94) and iatrogenic preterm birth (1.25 (1.10-1.42), 1.45 (1.26-1.68) 2.12 (1.57-2.86)) compared to women with normal BMI. Sensitivity analyses demonstrated for women with normal BMI in earlier pregnancies, becoming obese and morbidly obese in subsequent pregnancies was associated with increased risk of IOL, CS and neonatal unit admission >48 hours, respectively (all p<0.05). Conclusion Maternal obesity has adverse outcomes for obstetric and perinatal health for all pregnant women, regardless of parity.

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Aim To determine the effect of maternal body mass index (BMI) on inpatient costs for all pregnancies in Scotland, and outpatient costs for a separate cohort. Methods All women with singleton pregnancies, and estimable BMI, who delivered in Scottish maternity units between 01/01/2003 and 31/12/2009 were included (285,361 admissions, 123,931 pregnancies, 109,291 women). Duration of stay and provider data were combined with hospital level unit cost data to estimate the cost of each admission and total admission cost for each pregnancy. Outpatient costs were analysed in a separate cohort of women delivering in Edinburgh (n=5052). Women were grouped using WHO BMI criteria. The reference group for all analyses was BMI 18.5<25kg/m2. Data were analysed by ANOVA and a Generalised Linear Model adjusted for age, deprivation, hospital, smoking status. Results Mean (SD) number of admissions/pregnancy in underweight, normal, overweight, obese and morbid obesity were 2.40 (2.10), 2.14 (1.83), 2.3 (2.04), 2.64 (2.39), and 3.09 (2.87). Corresponding mean (SD) admission days were 3.58 (4.46), 3.31 (3.60), 3.47 (3.71), 3.79 (4.06) and 5.16 (3.97), respectively (p<0.01). Adjusted additional admission costs (mean (95% CI)) associated with underweight, overweight, obesity and morbid obesity were £172 (85-258), £157 (129-185), £474 (436-512) and £865 (767-963), respectively. Although attenuated, the U-shaped relationship between admission costs and BMI remained after ajusting for obstetric complications. Outpatient costs were also significantly higher (mean diff (95%CI)) in overweight (£22 (11-13)), obese (£53 (38-67)) and morbid obesity (£145 (96-193)), and ultrasound costs higher in underweight (£30 (13-46)) and morbid obesity (£99 (79-120))(unadjusted P <0.01). Conclusion Obesity has significant cost implications for maternity services independent of obstetric complications.