Maternal BMI and gestational weight gain reflect nutritional status before and during pregnancy. Some evidence has considered abnormal weight gain to have a significant relationship with poor pregnancy outcomes. However, weight gain in most pregnant women is not within normal range suggested by IOM .
For instance, our data indicates only half the subjects had a normal prepregnancy BMI (19.8–26 kg/m2). Furthermore, 50% of women with a normal BMI did not ultimately achieve the recommended weight gain. Abnormal weight gain was also seen in more than half of obese women (BMI > 29 kg/m2). Overall, there was no significant difference between the initial BMI and percentage of desired gestational weight gain.
Although 60% of low educated subjects were recognized with abnormal weight gain, we could not find any significant difference between weight gain and educational level. Although level of education did not influence weight gain significantly, but illiterate subjects were at higher risk for poor weight gain. This is perhaps explained by patient compliance and access to nutritional counseling and resources.
Previous studies have shown that pregnancy weight gain within the ranges recommended by IOM is associated with the best outcome for both mothers and infants [9, 10]. On the contrary, some studies, that retrospectively assessed the sensitivity and specificity of this indictor, concluded that maternal weight gain alone is neither a sensitive nor a specific predictor of poor pregnancy outcomes . Rasmussen et. al reported that constitutional low weight for height is not a predictor of complications during delivery, and no special observation of this group is recommended .
Since the amount of total weight gain is widely variable among women with good pregnancy outcomes, and the perinatal outcomes of interest are multifactorial in origin, it should not be expected for weight gain alone to be utilized as a perfect diagnostic or screening tool . Our study suggests that deviation in maternal weight gain can act as a useful marker of newborn weight at birth and, also pre-pregnancy BMI can predict fetal weight especially in women with BMI < 19.8 kg/m2. Ogunyemi et. al has mentioned that normal BMI and ideal weight gain in pregnancy is associated with decreased perinatal complications and an optimum birth weight . Another study showed that being moderately underweight was not associated with increased risk of adverse pregnancy outcomes, but being severely underweight was an important risk factor for reduced fetal growth .
Many studies looked more closely at the association between pregnancy weight gain and the rates of cesarean delivery.
In our study, weight gain was not associated with increased cesarean section rates, but frequency of cesarean section was significantly different among women in different levels of pre-pregnancy BMI, where, obese women experiencing the highest rate of cesarean. This is most likely explained based on the high incidence of large infants in this group. Another study showed that overweight status (25.0= BMI < 30.0 kg/m2) and obesity (BMI = 30.0 kg/m2) are only weak predictors of labor complications .
Steinfeld et.al reported obese Hispanic and African American women were more likely than obese white women to deliver by cesarean (P = 0.03). Therefore racial differences affect the complication rates in obese women, and may also influence prenatal counseling and pregnancy management . It is important to consider the underlying issues in controversy, as maternal anthropometry differs across ethnic groups and therefore different recommendations should be made for specific populations.
The relation between low pregnancy weight gain and increased risk of preterm birth was previously illustrated by Caminchael et. al . Although the biological mechanism underlining this association is unknown, it appears that a rate of pregnancy weight gain below the lower limit of the IOM's recommended range especially in late pregnancy may be related to a higher risk of preterm birth . Other studies have found that risk of preterm birth was not associated with maternal BMI . In our study there was no difference between weight gain and preterm delivery. This may be due to our data collection as we did not analyze weight fluctuations weekly, and therefore we were not able to assess any acute inappropriate weight gains, which may have occurred during period of a week.