Results
Maternal characteristics of women with insufficient GWG and women with the IOM recommended GWG are detailed in Table 1. In the total group (n = 314), age, ethnicity, family history of diabetes, smoking status, starting BMI, booking SBP and DBP week of GDM diagnosis, parity and first recorded HbA1C were not statistically significant between groups. On the 75g OGTT the 1-hour glucose value was higher (189mg/dL(10.5mmol/L) vs 181.8mg/dL (10.1 mmol/L) in women with GWG <5kg vs those with ideal GWG trending towards but not reaching statistical significance (p=0.05).
The groups were divided for further analysis into those treated with lifestyle intervention only (GDM-D) compared to those receiving insulin (GDM –I). In the GDM-I subgroup there were no differences in any of the baseline characteristics. In the GDM-D subgroup booking SBP (123.6mmHg vs 117.3mmHg; P<0.03) and DBP (73mmHg vs 68 mmHg; p<0.01) were significantly higher in women with GWG of <5kg compared to those with the recommended GWG. Both the 1-hour (189mg/dL(10.5mmol/L) vs 167.4 mg/dL(9.3mmol/L); p<0.01) and 2-hour (133.2mg/dL(7.4mmol/L) vs 118.8mg/dL(6.6 mmol/L); p=0.02) glucose values on the OGTT were significantly higher in those with GWG <5kg compared to those with the recommended GWG. Gestational week of delivery (38.9 vs 39.8, p=0.01) was lower in those with GWG <5kg compared to those with the recommended GWG. All other characteristics assessed were similar. On the 3-way analysis between women with insufficient GWG, the recommended amount of GWG and excessive amount of GWG, women with GWG <5kg were more likely to be older (34.4 years ±5.2 vs 33.8 years±4.5 vs 33.1 years ±5.4, p=0.01), to have a higher baseline BMI (37.1 kg/m2±5.4 vs 36.4 kg/m2±5.1 vs 35.5 kg/m2±4.5, p<0.01) and deliver earlier (38.8 weeks ± 2.1 vs 39.2weeks ±1.4 vs 39.2 weeks ±2.3, p<0.01).Women with GWG above the IOM recommendations were more likely to have a higher DBP at booking (73.4mmHg±9.1 vs 72.7mmHg±9.7 vs 70.3mmHg±9.4, p=0.01) and higher HbA1c levels (37.3mmol/mol ± 16.6 vs 35.3mmol/mol ± 8.8 vs 35.5mmol/mol ± 16.7) compared to women with GWG <5kg and women with GWG 5-9 kg.
Maternal outcomes are reported in Table 2. In the total group, women with GWG <5kg were more likely to have PPH (10% vs. 5.2%, p<0.01) or polyhydramnios (14.8% vs 5.3, p=0.03) compared to women with ideal GWG. On subgroup analysis, in the GDM-I group, women with GWG <5kg had higher rates of PPH (7.9% Vs 0%, p=0.05). In the GDM-D group, women with GWG <5kg were more likely to have PPH (13.2% Vs. 0%, p=0.03) and PIH (15.4% Vs 0%, p=0.02) compared to the ideal weight gain group. On the 3-way analysis between women with insufficient GWG, the recommended amount of GWG and excessive GWG, women with GWG <5kg were more likely to have higher rates of PPH (10%vs 5.2% vs 8.2%, p=0.02) and higher rates of polyhydramnios (14.8% vs 5.3% vs 5.2%, p<0.01). The higher rates of polyhydramnios were also found in the subgroup analysis in the GDM-I subgroup (20.1% vs 8.7% vs 5.2%, p< 0.01). Women with GWG above the IOM recommendations, were also more likely to have higher rates of PIH in the total group (18.5% vs 13.9% vs 6.6%, p=0.02) and in the GDM-D subgroup (20.1% vs 15.4% vs 0%, p=0.02).
Infant outcomes are shown in Table 3. The rates of LGA were higher in infants of GDM women with a GWG of <5kg compared to those who gained an ideal weight(17.3% vs 7.9%, p=0.04). On subgroup analysis, in the GDM-D group, the rate of prematurity was greater in infants of women with GWG <5kg (14.3% vs 0%, p=0.03). On the 3-way analysis between women with insufficient GWG, the recommended amount of GWG and excessive amount of GWG, infants of women with GWG <5kg were more likely to have a lower birth weight (3517.9g ± 566.6 vs 3563.2g ± 388.8 vs 3662.21± 604, p<0.01). However, there was no difference between groups in SGA rates (3.5% vs 1.3% vs 2.6%, p=0.50). Infants of women with GWG >9kg were more likely to have higher rates of macrosomia (26.6% vs 18.5% vs 15.6%, p=0.01) and LGA (23.5% vs 17.3% vs 7.9%, p<0.01) compared to the other 2 groups).
Logistic regression analysis (Table 4) determined that women with weight loss or GWG <5kg had higher odds ratios to develop PIH and polyhydramnios (OR 3, 95%CI 1.1-8.9, p=0.04; OR 3, 95%CI 1.1-8.1, p=0.04 respectively). However, when adjusted for baseline BMI, insulin use, smoking status, parity, family history, ethnicity and age, GWG <IOM recommendation in obese women with GDM was not associated with adverse outcomes.