Interpretation
Twin pregnancies are at a higher risk for gestational diabetes than singleton pregnancies, every additional fetus in multiple pregnancies increasing the risk for GDM by 1.8 times. Consistent with these studies, data of this analysis also showed a significant association between obesity and GDM, with significantly increasing rates within obesity classes. With GDM increasing the risks for cesarean sections, preeclampsia, and preterm birth, and considering the increasing rates of GDM worldwide, prevention and information on the risks of gestational diabetes should be extended.
Obesity has been established as an important risk factor for surgical site infections after cesarean sections. Almost a third of severely obese patients were described to suffer from wound complications after a cesarean section. This study confirms these findings, showing an association between maternal weight in general and especially obesity and wound complications. Furthermore, Olsen et al. and Wall et al. showed that missing antibiotic prophylaxis is an independent risk factor for wound infections and that patients with vertical skin incisions have a significantly increased incidence of wound complications. At the Buergerhospital Frankfurt, all cesarean sections are performed under antibiotic prophylaxis with a transverse skin incision, possibly explaining the low rates of wound healing disorders in our study.
PPH is the most important reason for pregnancy-related morbidity, 70% of all PPH being caused by uterine atony or inadequate uterine contraction. Maternal obesity and multiple pregnancies are considered being important risk factors for PPH, multifetal gestations possibly leading into uterine overdistension, and consequently into uterine atony with the risk of PPH. To our knowledge, this study was the first to assess the direct influence of maternal weight on uterine atony both with the necessity of Sulprostone and intervention with a Bakri Balloon in twin pregnancies. In contrast to the studies mentioned afore, rates of PPH did not reach significance in this study, however, women with obesity class I had a threefold risk for PPH compared to obesity class II and a twofold risk for PPH compared to obesity class III.
Paidas Teefey et al. investigated rates of cesarean deliveries especially for obesity class III women in singleton pregnancies, finding rates of nearly 50% for obesity class III women and 66% for women with a BMI of at least 50 kg/m2. Albeit not statistically significant, this study confirmed these findings, showing that cesarean sections were more common with rising BMI, especially in the obese group.
Despite being a study conducted in singleton pregnancies and thus only partially applicable to twins, Bicocca et al. observed a higher risk for hypertensive pregnancy disorders, including preeclampsia, with increasing obesity classes. In twin pregnancies, findings on preeclampsia are inconsistent. On one hand, a BMI ≥30 kg/m2 is considered as a significant risk factor for preeclampsia, on the other hand, the risk for preeclampsia might only be significantly increased in obesity class III. Potentially due to low rates of preeclampsia in this study population, findings of this study contrast the studies mentioned afore, showing no significant risks.
In singleton pregnancies, obesity was shown to be the second biggest risk factor for stillbirth. Similarly, Salihu et al. described a 60% higher risk for fetal death of both twins in obese women. Both these findings contrast the results of this study, possibly because of low rates of IUD in this study in general and similar rates in all weight groups.
Neonatal outcomes in twin pregnancies have only been investigated in a few studies, while having been analyzed thoroughly in singleton pregnancies. Obesity or increasing BMI were shown to be associated with higher rates of fetomaternal complications as well as admission to NICU in singleton pregnancies. Confirming these findings, a significantly higher risk for admission to NICU in neonates of obesity class III mothers and especially for their firstborn was observed. Maternal weight did not have an impact on the mean length of stay in the NICU.
Only a few studies have been conducted in twins investigating the topic of asphyxia and low umbilical artery pH, concluding that the second twin is at a significantly higher risk for asphyxia, low umbilical artery pH values or low APGAR scores. To our knowledge, this study is the first one to assess the impact of maternal weight and obesity on the umbilical artery pH and asphyxia in twins. Significantly higher rates of pH values of 7.01 – 7.1 in neonates of obese mothers were observed in this study. Considering the sparse number of studies on this topic, the impact of obesity on the risk for asphyxia in twins should be analyzed in further investigations. Regarding the five-minute APGAR score, our findings confirmed those of Bautista et al., showing no association between maternal BMI and a low five-minute APGAR score.