Table 2

Effect of dietary and lifestyle interventions in pregnancy on secondary maternal outcomes (ranked as critically important by Delphi survey, except for vaginal delivery and gestational age at birth). Summary estimates are relative risks unless stated otherwise

	No of studies	No of participants	Summary estimate (95% CI)	P value	I² (%)
Dietary intervention
Gestational diabetes mellitus	3^{33 35 36}	409	0.39 (0.23 to 0.69)	0.001	21
Pre-eclampsia	6^{28 30 31 34-36}	2624	0.67 (0.53 to 0.85)	<0.001	0
Gestational hypertension	2^{35 36}	282	0.30 (0.10 to 0.88)	0.03	0
Preterm delivery	4^{26 30 31 35}	1474	0.68 (0.48 to 0.96)	0.03	35
Caesarean section	5^{28 29 31 35 36}	2273	0.93 (0.84 to1.04)	0.19	49
Vaginal delivery	2^{31 34}	472	0.97 0.89 to 1.07)	0.56	0
Induction of labour	4^{28 31 34 35}	2277	1.12 (0.99 to 1.27)	0.07	60
Postpartum haemorrhage	2^{28 35}	1232	0.90 (0.57 to 1.42)	0.64	0
Gestational age at delivery (weeks)	6^{28 30-32 34 35}	2625	−0.05* (−0.18 to 0.08)	0.42	71
Physical activity
Gestational diabetes mellitus	0	—	—	—	—
Pre-eclampsia	0	—	—	—	—
Gestational hypertension	0	—	—	—	—
Preterm delivery	5^{37 38 46 52 53}	450	1.22 (0.51 to 2.90)	0.65	0
Caesarean section	5^{37 39 48-50}	542	0.88 (0.66 to 1.17)	0.38	0
Vaginal delivery	3^{37 39 49}	488	1.02 (0.93 to 1.11)	0.70	0
Induction of labour	0	—	—	—	—
Postpartum haemorrhage	0	—	—	—	—
Gestational age at delivery (weeks)	11^{37-39 42 44-49 54}	1250	0.03* (−0.14 to 0.20)	0.74	0
Mixed approach
Gestational diabetes mellitus	6^{61 62 63 65-67}	1233	1.18 (0.78 to 1.77)	0.44	0
Pre-eclampsia	4^{59 63 65 66}	718	1.16 (0.70 to 1.90)	0.57	39
Gestational hypertension	4^{59 63 65 66}	779	1.08 (0.75 to 1.55)	0.69	42
Preterm delivery	4^{57 63 65 66}	728	0.90 (0.55 to 1.47)	0.68	7
Caesarean section	8^{56 57 59 61 63 65-67}	1407	0.94 (0.79 to 1.13)	0.53	10
Vaginal delivery	1⁵⁷	34	1.25 (0.88 to 1.78)	0.21	NA
Induction of labour	1⁵⁹	85	1.17 (0.78 to 1.75)	0.44	NA
Postpartum haemorrhage	0	—	—	—	—
Gestational age at delivery (weeks)	6^{57 59 61 62 65 66}	813	0.20* (−0.02 to 0.42)	0.07	1
All interventions
Gestational diabetes mellitus	9	1642	0.78 (0.57 to 1.08)	0.13	29
Pre-eclampsia	10	3342	0.74 (0.60 to 0.92)	0.006	31
Gestational hypertension	6	1061	0.89 (0.64 to 1.25)	0.51	50
Preterm delivery	13	2652	0.78 (0.60 to 1.02)	0.07	0
Caesarean section	18	4222	0.93 (0.85 to 1.01)	0.10	3
Vaginal delivery	6	994	1.00 (0.94 to 1.07)	0.91	0
Induction of labour	5	2362	1.12 (1.00 to 1.26)	0.05	47
Postpartum haemorrhage	2	1232	0.90 (0.57 to 1.42)	0.64	0
Gestational age at delivery (weeks)	23	4688	0.02* (−0.08 to 0.11)	0.72	33

NA=not applicable.

*Mean difference.