To examine the likelihood of classical hysterotomy across preterm gestational ages and to identify factors that increase its occurrence.
This is a secondary analysis of a prospective observational cohort collected by the Maternal-Fetal Medicine Network of all women with singleton gestations who underwent a cesarean delivery with a known hysterotomy. Comparisons were made based on gestational age. Factors thought to influence hysterotomy type were studied, including maternal age, body mass index, parity, birth weight, small for gestational age (SGA) status, fetal presentation, labor preceding delivery, and emergent delivery.
Approximately 36,000 women were eligible for analysis, of whom 34,454 (95.7%) underwent low transverse hysterotomy and 1,562 (4.3%) underwent classical hysterotomy. The median gestational age of women undergoing a classical hysterotomy was 32 weeks and the incidence peaked between 24 0/7 weeks and 25 6/7 weeks (53.2%), declining with each additional week of gestation thereafter (P for trend <.001). In multivariable regression, the likelihood of classical hysterotomy was increased with SGA (n=258; odds ratio [OR] 2.71; confidence interval [CI] 1.78–4.13), birth weight 1,000 g or less (n=467; OR 1.51; CI 1.03–2.24), and noncephalic presentation (n=783; OR 2.03; CI 1.52–2.72). The likelihood of classical hysterotomy was decreased between 23 0/7 and 27 6/7 weeks of gestation and after 32 weeks of gestation when labor preceded delivery, and increased between 28 0/7 and 31 6/7 weeks of gestation and after 32 weeks of gestation by multiparity and previous cesarean delivery. Emergent delivery did not predict classical hysterotomy.
Fifty percent of women at 23–26 weeks of gestation who undergo cesarean delivery have a classical hysterotomy, and the risk declines steadily thereafter. This likelihood is increased by fetal factors, especially SGA and noncephalic presentation.
The likelihood of classical hysterotomy is 54% at 24 weeks of gestation, declines with advancing gestation, and increases with noncephalic presentation and low birth weight.
Department of Obstetrics and Gynecology, Lucille Packard Children's Hospital, Stanford University School of Medicine, Stanford, and the Department of Obstetrics and Gynecology, Santa Clara Valley Medical Center, San Jose, California.
Corresponding author: Sarah Osmundson, MD, 300 Pasteur Drive, HH333 MC 5317, Stanford, CA 94305; e-mail: email@example.com.
The authors thank the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the Maternal-Fetal Medicine Units Network, and the Protocol Subcommittee in making the database available on behalf of the project. The contents of this report represent the views of the authors and do not represent the views of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network or the National Institutes of Health.
Financial Disclosure The authors did not report any potential conflicts of interest.