Characteristics of study population
| Variables | Median, (IQR) or n, (%) | N |
| Age (years) | 31 (28–34) | 196 |
| Nulliparous | 93 (48%) | 196 |
| Multiparous | 103 (52%) | 196 |
| Smoking before pregnancy | 14 (7%) | 192 |
| Non-smoking at first antenatal visit | 178 (93%) | 192 |
| IVF | 11 (6%) | 183 |
| Height at first antenatal visit, cm | 168 (163–173) | 196 |
| Weight at first antenatal visit, kg | 67 (61–75) | 195 |
| BMI at first antenatal visit | 24 (22–27) | 196 |
| BP systolic at first antenatal visit, mm Hg | 112 (107–120) | 195 |
| BP diastolic at first antenatal visit, mm Hg | 65 (60–70) | 195 |
| Gestational age at first antenatal visit, weeks | 10 (10–11) | 196 |
| Gestational age at second visit, weeks | 22 (21–24) | 163 |
| Gestational age at delivery, weeks | 40 (39–41) | 179 |
| Epidural anaesthesia | 77 (43%) | 179 |
| Spontaneous vaginal delivery | 148 (83%) | 179 |
| Elective caesarean delivery | 14 (8%) | 179 |
| Emergency caesarean delivery | 12 (7%) | 179 |
| Assisted vaginal delivery | 5 (3%) | 179 |
| Oxytocin as labour augmentation | 69 (39%) | 178 |
| Oxytocin postpartum only | 96 (54%) | 178 |
| Postpartum haemorrhage >1000 mL | 25 (14%) | 177 |
| Birth weight (g) | 3618 (3322–4020) | 178 |
| Time delivery to blood sample (hours) | 26 (17–34) | 122 |
| Time delivery to postpartum visit (months) | 7 (6–8) | 150 |
BMI, body mass index; BP, blood pressure; IVF, in vitro fertilisation.