Giles 2003

Methods	Multi‐centred randomised controlled trial ‐ block randomisation, block of 20. Individual women, 2‐trial arm.
Participants	Women with twin pregnancies (monochorionic and dichorionic) at 25 weeks. 2 viable apparently normally formed fetuses seen on ultrasound scan. Exclusions: fetal anomalies; polyhydramnois/oligohydramnois; demise of 1 twin before 25 weeks. Significance of chorionicity not realised at time randomisation began so no attempt was made to assess chorionicity. N = 539 women.
Interventions	Intervention: Doppler and biometry ultrasound. Doppler + biometry at 25, 30 and 35 weeks; “the clinicians were advised to undertake interventions if there was an abnormal umbilical artery Doppler study (> 95th centile systolic diastolic ratio) or abnormal ultrasound biometry indicating discordant growth. The suggested intervention was intensive surveillance by obstetrics caregivers...if other indicators of fetal well‐being (lack or serial growth, decreased amniotic fluid or abnormal fetal monitoring) were abnormal, the early delivery was advised after 25 weeks; “An abnormality of Doppler waveforms themselves was not considered an indication for immediate delivery unless there was absence of diastolic flow velocity at > 32 weeks of gestation”. Comparison: biometry ultrasound. Biometry only at 25, 30 and 35 weeks.
Outcomes	Maternal: antenatal admission, presence of hypertension, gestation at delivery, indication for delivery and mode of delivery. Fetal: ultrasound biometry measurements, umbilical artery doppler systolic diastolic ratios and the occurrence of fetal death and causative factors. Neonatal: birthweight, Apgar scores, admission to NICU, admission to special care nursery, requirements for ventilation and occurrence of neonatal death (up to 28 days of life).
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	“....opaque sealed envelopes containing the randomisation code the envelope being opened by an observer remote from patient care”.
Allocation concealment (selection bias)	Low risk	“....opaque sealed envelopes containing the randomisation code the envelope being opened by an observer remote from patient care".
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Blinding women and/or staff in these trials was not generally feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinding women and/or staff in these trials was not generally feasible.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Describe any loss of participants to follow‐up at each data collection point: 539 women were randomised in Doppler Assessment in multiple pregnancy (DAMP) study: Doppler 268 and control 271. 13 were lost to follow‐up after randomisation at 25 weeks and were not included in the results. This left 526 women with complete follow‐up 262 in Doppler and 264 in no Doppler.                              Describe any exclusion of participants after randomisation: was the analysis ITT? If not have the data been able to be re‐included? 7 women in the no Doppler group had Doppler.
Selective reporting (reporting bias)	Unclear risk	There seems to be no evidence of selective reporting bias but we have not assessed the trial protocol.
Other bias	Low risk	If the study was stopped early, explain the reasons: not stopped early but PNM on which power calculation was much lower than expected. Power calc on 85.7/1000 and in reality 11/1000 so study significantly underpowered ‐ needed 3300 per arm. Describe any baseline in balance: no imbalances.