ketonuria, and in pregnant nondiabetic women, only 7 percent developed ketonuria. Measurement of blood ketones was never positive if the urine measure was ≤ 2 plus and acetoacetate levels were always less than 1 mmol/L. There was no difference in neonatal outcomes among the three groups.
In summary, pregnant women are more likely to develop elevated measures of blood βHA and acetoacetate during prolonged fasting (after 12-18 hours) as a result of the metabolic and hormonal changes that occur during pregnancy. Although pregnant women with diabetes are more likely to develop elevated blood ketones than women with normal glucose tolerance, a substantial proportion of pregnant women with normal glucose tolerance have elevated blood ketone levels at some time during gestation. Although the evidence is based on associations and does not demonstrate causality, caution should be exercised regarding weight loss during pregnancy or no GWG, given the propensity to develop ketonemia, increased urinary nitrogen excretion, and decreased gluconeogenic amino acids. As discussed in Chapter 6, there are significant consequences of caloric insufficiency, low GWG, and poorly controlled diabetes for the child, and these are discussed in Chapter 6.
Total GWG in normal-term pregnancies displays considerable variability; nevertheless, some generalizations can be made regarding mean tendencies and patterns of GWG:
A consistent inverse relationship is observed between GWG and pregravid BMI category.
Mean GWG ranges from 10.0 to 16.7 kg in normal weight adults and 14.6 to 18.0 kg in adolescents giving birth to term infants.
The pattern of GWG is most commonly described as sigmoidal, with mean weight gains higher in the second than the third trimester across BMI categories, except for obese women.
Lower GWGs, on the order of 11 kg and 9 kg, have been confirmed in large cohorts of obese women and very obese women, respectively.
In its evaluation of GWG in multiple pregnancies, the committee relied on observational GWG data of women giving birth to twins born at 37-42 weeks of gestation and with an average twin birth weight ≥ 2,500 g: