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Maternal and neonatal outcomes among obese women

Paper: Maternal and neonatal outcomes among obese women with weight gain below the new Institute of Medicine recommendations.

Midwives magazine: Issue 5 :: 2011

Paper | Maternal and neonatal outcomes among obese women with weight gain below the new Institute of Medicine recommendations.
Author | Blomberg M.
Publication | Obstetrics & Gynecology 2011; 117(5): 1065-70.

In this population-based cohort study, the author set out to estimate whether weight loss or low gestational weight gain in class I-III obese women is associated with adverse maternal and neonatal outcomes compared with gestational weight gain within the new Institute of Medicine (IoM) recommendations, which stated that the optimal gestational weight for obese women, or body mass index, (BMI) is 30 or higher.

The cohort consisted of 46,595 women with a BMI of 30 or higher with available data on gestational weight gain. The women gave birth in Sweden between 1 January 1993 and 31 December 2008. Midwives recorded pre-pregnancy maternal weight and height at the first antenatal visit. The women were divided into four gestational weight gain categories: less than 0kg (weight loss), 0-4.9kg (low weight gain), 5-9kg (recommended weight gain) and more than 9kg (excessive weight gain). Outcomes studied were pre-eclampsia, the rate of caesarean delivery, instrumental vaginal delivery, small- and large-for-gestational age neonate, fetal distress and low Apgar score (less than seven at five minutes). Women with a diagnosis of diabetes were not removed from the analysis.

The overall percentage of obese women gaining weight within the IoM guidelines was 27.3. The proportion of women with excessive weight gain (more than 9kg) was: class I (59.8%), class II (48.4%) and class III (39.6%). There were no significant differences among the three obesity classes concerning the number of women gaining the recommended weight (5-9kg). Obese women, irrespective of obesity class, who lose weight during pregnancy, seem to have a decreased risk of caesarean delivery and large-for-gestational-age-births and no significant increased risk for pre-eclampsia, excessive bleeding during delivery, instrumental delivery, low Apgar score, or fetal distress. Small-for-gestational-age births were found to be uncommon among obese women (1.2-3.8%) despite gestational weight gain. The risk for small-for-gestational-age is two-fold increased in obesity classes I and III among women who lose weight compared with women with recommended weight gain. The increased risk for small-for-gestational-age disappears among women with low weight gain in obesity class III, but persists in obesity class I. Class III obese women with high weight gain have no decreased risk of small-for-gestational-age. Large-for-gestational-age births occur in one of five among the heaviest women with excessive weight gain. Obese women in class I-III with low weight gain (0-5kg) do not differ markedly compared with obese women losing weight, concerning both obstetric and neonatal outcome. There is an increased risk of adverse outcomes in obesity class II women with excessive weight gain. Excessive weight gain did not decrease the risk for small-for-gestational-age in obesity class III.

Excessive weight gain substantially increases the risk of postpartum weight retention, states the author. They conclude that it seems reasonable for class II and III obese women to lose weight because the risk decreases or remains unaffected for all adverse outcomes identified. 

Obese women (class II and III) who lose weight during pregnancy seem to have a decreased risk or unaffected risk for a number of obstetric complications, both maternal and neonatal.

Jan wallis is a retired midwife and senior lecturer