Table 1

Effect of dietary and lifestyle interventions in pregnancy on primary outcomes (weight gain in pregnancy and birth weight) and secondary weight related outcomes ranked as critically important by Delphi survey (except for exceeding IOM recommendations)

	No of studies	No of participants	Summary estimate (95% CI)	P value	I² (%)
Dietary intervention
Weight gain in pregnancy (kg)	10^{25-28 31-36}	2560	−3.84* (−5.22 to −2.45)	<0.001	92
Birth weight (g)	10^{26-28 30-36}	2861	−60* (−190 to 80)	0.41	84
Small for gestational age	3^{28 30 31}	2252	1.02† (0.75 to 1.37)	0.91	0
Large for gestational age	5^{28 29 31 34 35}	2378	0.78† (0.51 to 1.19)	0.26	63
Exceeds IOM recommendations	0	—	—	—	—
Physical activity
Weight gain in pregnancy (kg)	14^{37-39 42 43 45-48 50-54}	1057	−0.72* (−1.20 to −0.25)	0.003	30
Birth weight (g)	14^{37-40 42 44-50 52 53}	1369	−60* (−120 to −10)	0.02	0
Small for gestational age	4^{37 38 46 53}	409	1.28† (0.52 to 3.15)	0.60	0
Large for gestational age	4^{38 39 46 52}	355	0.52† (0.25 to 1.09)	0.08	0
Exceeds IOM recommendations	1⁴⁶	74	0.33† (0.11 to 0.98)	0.05	NA
Mixed approach
Weight gain in pregnancy (kg)	10^{7 56 59-63 65-67}	1864	−1.06* (−1.67 to −0.46)	<0.001	36
Birth weight (g)	7^{57 59 61-63 65 66}	1048	10* (−50 to 70)	0.86	0
Small for gestational age	4^{58 63 65 66}	891	0.88† (0.53 to 1.44)	0.60	0
Large for gestational age	9^{57-59 61 62 63 65-67}	1500	1.05† (0.79 to 1.40)	0.72	0
Exceeds IOM recommendations	4^{61 63 65 66}	899	0.89† (0.71 to 1.13)	0.33	56
All interventions
Weight gain in pregnancy (kg)	34	5481	−1.42* (−1.89 to −0.95)	<0.001	80
Birth weight (g)	31	5278	−50* (−100 to 0)	0.08	57
Small for gestational age	11	3552	1.00† (0.78 to 1.28)	0.99	0
Large for gestational age	18	4233	0.85† (0.66 to 1.09)	0.21	38
Exceeds IOM recommendations	5	873	0.85† (0.66 to 1.11)	0.21	60

IOM=Institute of Medicine; NA=not applicable.

*Mean difference.

†Relative risk.