Comment: The quality of evidence is upgraded by consistent findings and dose-response effect.
A meta-analysis «Goldstein RF, Abell SK, Ranasinha S et al. Associa...»1 included including 23 trials (n=1 309 136 ) evaluated the Institute of Medicine (IOM) guidelines (see below table «Recommended weight gain in pregnancy (IOM guideline 2009) ...»1) and maternal and infant outcomes. Gestational weight gain (GWG) was below or above IOM guidelines in 23% and 47% of pregnancies, respectively. GWG below the recommendations was associated with higher risk of small for gestational age (SMA) (OR 1.53, 95% CI 1.44 to 1.64), absolute risk difference (ARD) 5% and preterm birth (OR 1.70, 95% CI 1.32 to 2.20), ARD, 5%, and lower risk of large for gestational age (LGA) (OR 0.59, 95% CI 0.55 to 0.64), ARD -2%, and macrosomia (OR 0.60, 95% CI 0.52 to 0.68), ARD -2%. GWG above the recommendations was associated with lower risk of SGA (OR 0.66, 95% CI 0.63 to 0.69), ARD -3% and preterm birth (OR 0.77, 95% CI 0.69 to 0.86), ARD -2% and higher risk of LGA (OR 1.85, 95% CI 1.76 to 1.95), ARD 4%, macrosomia (OR 1.95, 95% CI 1.79 to 2.11), ARD 6%, and caesarean delivery (OR 1.30, 95% CI 1.25 to 1.35), ARD 4%. Gestational diabetes (GDM) could not be evaluated.
| BMI before pregnancy | Recommended weight gain (kg) |
|---|---|
| < 18.5 | 12.5 – 18.0 |
| 18.5 – 24.9 | 11.5 – 16.0 |
| 25.0 – 29.9 | 7.0 – 11.5 |
| ≥ 30 | 5.9 – 9.0 |
Another systematic review and meta-analysis «...»5 included 54 studies with a total of 30 245 946 pregnancies. Compared with women who gained weight as recommended in the guidelines, those who gained less weight had lower odds for LGA neonates, for preeclampsia, and for cesarean delivery (table «Outcomes with weight gain below the current guidelines compared with within the guidelines for all classes of maternal obesity...»2), no heterogeneity, P<00001, except for preeclampsia class III. The incidence of small for gestational age neonates was below the expected limits (<10%) and was not associated with increased neonatal morbidity.
| Outcome | Odds ratio (95% confidence interval) | ||
|---|---|---|---|
| BMI 30-34.9 kg/m2 (class I) | BMI 35-39.9 kg/m2 (class II) | BMI > 40 kg/m2 (class III) | |
| Large for gestational age | OR 0.69 (0.64 to 0.73) | OR 0.68 (CI 0.63 to 0.74) | OR 0.65 (0.57 to 0.75) |
| Preeclampsia | OR 0.71 (0.63 to 0.79) | OR 0.82 (0.73 to 0.91) | OR 0.82 (0.70 to 0.94) |
| Caesarean delivery | OR 0.76 (0.72 to 0.81) | OR 0.82 (0.77 to 0.87) | OR 0.87 (0.82 to 0.91) |
| Postpartum weight retention | 0.20 (0.05 to 0.82) in the overall obesity group (P=0.03) | ||
| Composite neonatal morbidity | 0.93 (0.87 to 0.99) in the overall obesity group (P=0.04) | ||
Another meta-analysis «Rogozinska E, Zamora J, Marlin N et al. Gestationa...»3 analyzed individual participant data (IPD) of healthy women with a singleton pregnancy and a BMI of 18.5 or more from the control arms of 36 randomised trials (16 countries). Out of 4429 women (from 33 trials), two thirds gained weight outside the IOM recommendations (1646 above; 1291 below). The median GWG outside the IOM recommendations was 3.1 kg above and 2.7 kg below. In comparison to GWG within the IOM recommendations, GWG above was associated with increased odds of caesarean section (aOR 1.50, 95% CI 1.25 to 1.80), LGA (aOR 2.00, 95% CI 1.58 to 2.54), and reduced odds of SGA (0.66, 95% CI 0.50 to 0.87); no significant effect on preterm birth was detected. The relationship between GWG below the IOM recommendation and caesarean section or LGA was inconclusive; however, the odds of preterm birth (aOR 1.94, 95% CI 1.31 to 2.28) and SGA (aOR 1.52, 95% CI 1.18 to 1.96) were increased.
A systematic review and meta-analysis «Teede HJ, Bailey C, Moran LJ et al. Association of...»4 evaluating the association of different types of diet and physical activity-based antenatal lifestyle interventions with gestational weight gain (GWG) and maternal and neonatal outcomes included 117 RCTs with a total of 34 546 women. Compared with routine care, diet was associated with less GWG (-2.63 kg; 95% CI, -3.87 to -1.40) than physical activity (-1.04 kg; 95% CI, -1.33 to -0.74) or mixed interventions (eg, unstructured lifestyle support, written information with weight monitoring, or behavioral support alone) (-0.74 kg; 95% CI, -1.06 to -0.43). Diet was associated with reduced risk of GDM (OR, 0.61; 95% CI, 0.45 to 0.82), preterm delivery (OR, 0.43; 95% CI, 0.22 to 0.84), large for gestational age neonate (OR, 0.19; 95% CI, 0.08 to 0.47), neonatal intensive care admission (OR, 0.68; 95% CI, 0.48 to 0.95), and total adverse maternal (OR, 0.75; 95% CI, 0.61 to 0.92) and neonatal outcomes (OR, 0.44; 95% CI, 0.26 to 0.72). Physical activity was associated with reduced GWG and reduced risk of GDM (OR, 0.60; 95% CI, 0.47 to 0.75), hypertensive disorders (OR, 0.66; 95% CI, 0.48 to 0.90), cesarean section (OR, 0.85; 95% CI, 0.75 to 0.95), and total adverse maternal outcomes (OR, 0.78; 95% CI, 0.71 to 0.86). Diet with physical activity was associated with reduced GWG (-1.35 kg; 95% CI, -1.95 to -0.75) and GDM (OR, 0.72; 95% CI, 0.54 to 0.96) and total adverse maternal outcomes (OR, 0.81; 95% CI, 0.69 to 0.95).
A retrospective observational study «Aiken CEM, Hone L, Murphy HR et al. Improving outc...»2 assessed whether weight control after GDM diagnosis improves outcomes (n=546). Higher total gestational weight gain was associated with caesarean section (OR 1.05, 95% CI 1.02 to 1.08, P < 0.001) and LGA (OR 1.08, 95% CI 1.03 to 1.12, P < 0.001). Higher late gestational weight gain (28–36 weeks; n = 144) was associated with LGA (OR 1.17, 95% CI 1.01 to 1.37, P < 0.05), instrumental deliveries (OR 1.26, 95% CI 1.03 to 1.55, P < 0.01), higher total daily insulin doses (36 weeks; beta coefficient 4.37, 95% CI 1.92–6.82, P < 0.001).
A retrospective cohort study «...»6 included 30 910 pregnant women. 7569 pregnancy women had less than recommended GWG, 13 088 had adequate GWG, and 10 253 had excessive GWG. The incidence of macrosomia and LGA continues to increase from inadequate GWG to excessive GWG groups (dose-response). Pregnant women without GDM who have excessive GWG were at higher risk of macrosomia (a-OR 2.19; 95% CI 1.83 to 2.63) and LGA (a-OR 2.19, 95% CI 1.89 to 2.54) than pregnant women with GDM. Moreover, this risk increased with increasing pre-pregnancy BMI. Only those with inadequate GWG and pre-pregnancy BMI < 18.5 kg/m2 had an increased risk of SGA.