Study population and data collection
Retrospective data analysis of fresh cycles from 2009-2017 at Repromed (Dulwich, South Australia and Darwin, Northern Territory clinics). Cycles including either in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) with autologous sperm and eggs and the transfer of a single blastocyst embryo were assessed (Figure S1). First singleton term birth (≥ 37 weeks’ gestation) with a birth weight recorded were included in the analysis. Pre-term (<37 weeks’ gestation), twin births and second pregnancies from the same patient couple were excluded from the analysis (Figure S1). Parental data was collected from case notes including demographic data (socioeconomic index for areas (SEIFA), ART information (insemination method and infertility diagnosis) and maternal and paternal age. SEIFA was calculated by patient’s postcode 12. A high score indicates greater social advantage, while a low score indicates relatively greater disadvantage; the average SEIFA score is 1000 and the middle two-thirds of SEIFA scores will generally fall between ~900 and 1100 12.
Birth outcomes including infant birthweight (g), gestational age (weeks), sex (male/female), twin deliveries, and delivery method (vaginal/caesarean), were supplied by the treating obstetrician as per the ART treatment act that indicates mandatory reporting to the Australian and New Zealand Assisted Reproduction Database (ANZARD). Small for gestational age (SGA) infants were classified as ≤10th percentile, while large for gestational age (LGA) infants were classified as ≥90th percentile, based on Australian specific birthweight standards reported in Dobbinset al. 13.