Research Project

A Feasibility Study for Comparing Endogenous Oxytocin, Endogenous Vasopressin, and Oxytocin Receptor Methylation Across Body Mass Index Groups for Women Experiencing Labor Induction at Term

Principal Investigator
Maeder, Angela B.
Funding Source
Internal Research Support Program

Abstract

Nearly 4 million women give birth in the U.S. annually, and greater than 1 in 5 of these women were obese prior to becoming pregnant. Women who are obese are more likely to experience induction of labor (IOL) for conditions including hypertension, diabetes, and post-dates pregnancy than women who are non-obese, and IOL rates for all women have nearly tripled in the last 30 years. Intravenous (IV) oxytocin (OT; Pitocin) is the most commonly used medication for IOL, and was listed by the Institute for Safe Medication Practices as one of 12 high-alert (can cause significant harm if used in error) medications. Our previous study showed that women who were obese had longer labor length, higher rates of cesarean delivery, and received more IV OT than women who were non-obese. Recent animal and human studies have shown that endogenous levels of OT are related to food intake and weight gain. Another peptide, vasopressin (AVP) is structurally similar to OT, also causes uterine contraction, and each peptide can bind to the other?s receptor. In addition to differences in endogenous OT and AVP levels, there may be a dysfunction at the receptor level related to differences in uterine contractility and birth outcomes across BMI groups. The aims of this study are to 1) test the feasibility of measuring endogenous OT, endogenous AVP, and OT receptor gene DNA methylation marks for women between BMI groups, and 2) determine the effect size needed for each of these measures when controlling for potential confounders. Thirty women will be recruited upon admission to a Labor and Delivery (L&D) unit for IOL at 40 weeks gestation or greater. Women who had a BMI < 30.0 at the initiation of prenatal care during the first trimester will be considered non-obese (n=15), and women who had a BMI > 30.0 at initiation of prenatal care will be considered obese (n=15). At the initiation of the IV line, before any medications have been administered, one tube of blood will be drawn in addition to the tube drawn routinely on all women at the study site. This additional tube of blood will be analyzed for levels of endogenous OT, endogenous AVP, and OT receptor gene DNA methylation marks. At the completion of the study, outcome measures for recruitment, and measures of biological specimens will be analyzed, and effect sizes will be calculated for differences in endogenous OT, endogenous AVP, and OT receptor gene DNA methylation marks. Descriptive statistics including means, and standard deviations will be calculated, and we will explore any differences between groups using t-tests. Multiple linear regression models will be used to calculate effect size using group mean differences for endogenous OT, endogenous AVP, and OT receptor gene DNA methylation marks.