Compared with normal-weight women, obese women are twice as likely to undergo labor induction (Denison, 2008). Unfortunately, obese women are also twice as likely to experience a failed induction, and this risk rises with greater degrees of obesity (Wolfe, 2011). In a retrospective analysis of 470 nul liparous women with a BMI >30 kg/mrand an unfavorable cervix, those who underwent labor induction at 39 weeks' gestation were compared with those expectantly managed beyond 39 weeks (Wolfe, 2014). Two thirds of pregnancies expectantly managed either labored or had spontaneously ruptured membranes. Compared with this cohort, those who underwent planned labor induction had an elevated cesarean delivery rate-26 versus 40 percent. Moreover, their newborns were more frequently admitted to the neonatal intensive care unit-6 versus 18 percent. Conversely, Lee and associates (2016) reviewed statistics from 74,725 deliveries in obese women and reported that elective induction at 37 to 39 weeks in nulliparas and especially multiparas was actually associated with a lower cesarean delivery rate. hese conflicting results highlight the diiculties faced by obstetrical providers as they contemplate the seemingly competing interests of the fetus and the obese mother. To address this, the Maternal-Fetal Medicine Units Network is conducting a randomized trial of planned labor induction at 39 weeks' gestation in nulliparous women.
Obese women present anesthesia challenges that include diicult epidural and spinal analgesia placement and complications from failed or diicult intubations. Evaluation of super-morbidly obese gravidas by the anesthesiologist is recommended during prenatal care or upon arrival to the labor unit (American College of Obstetricians and Gynecologists, 2017). Although the rationale for antepartum anesthesia consultation and early epidural analgesia access seems logical, little published data truly demonstrates benefits from these practices (Eley, 2016) .
Regional analgesia for morbidly obese women is associated with longer neuraxial procedure times and more failed placement attempts (Tonidandel, 2014). Importantly, however, spinal analgesia in obese women for cesarean delivery does not appear to have benefits over combined spinal-epidural. For example, Ross and colleagues (2014) compared single-shot spinal analgesia with combined spinal-epidural analgesia and found that both methods could be placed with equal expediency and function similarly in morbidly obese patients.
Obese women who undergo regional analgesia that is complicated by relative hypotension more frequently have neonates with umbilical artery cord blood acidemia, probably due to delayed delivery. Edwards and colleagues (2013) studied 5742 obese women and found that pH significantly dropped, and base deficit rose, with increasing BMI. The rate of pH <7.1 doubled from 3.5 percent for a BMI <25 kg/mrto 7.1 percent for a BMI ::40 kg/mr. Anesthetic risks and complications are discussed in more detail in Chapter 25.