In a recent study published in the journal PLoS ONE, researchers investigate the association between excessive weight gain during pregnancy and the subsequent risk of prolonged labor or comorbid complications during delivery in Japanese women.
Study: Maternal excessive weight gain as a potential risk factor for prolonged labor in Japanese pregnant women: The Japan Environment and Children’s Study. Image Credit: aslysn / Shutterstock.com
The risks of prolonged labor
Prolonged labor, which is colloquially known as failure to progress, is a suboptimal and often dangerous pattern of labor wherein the delivery of the infant progresses at a very slow pace. This condition can result in labor halting indefinitely at either the first or second stage of labor and can have severe and long-term consequences for the mother and infant, including death.
Despite affecting only 8% of all pregnant women, incidences of prolonged labor are rising globally, with the condition representing one of the most common labor complications in the world. While decades of research have explored different approaches that can be used to accelerate labor to minimize clinical harm to the mother and her newborn, few studies have identified the risk factors associated with prolonged labor.
Nulliparity, the use of regional anesthesia, older maternal age, high birth weight, smaller maternal stature, and excessive maternal weight gain may increase the risk of prolonged labor. In particular, excessive maternal weight gain has been evaluated in clinical settings, with results suggesting its association with increased failure to progress risk.
Many of these studies used small sample sizes, included biased participant selection, and produced slightly contradicting results. Furthermore, all studies on this topic included only American or European women.
About the study
Given the potential role of stature in prolonged labor risk and the significant role of ethnicity in defining stature, investigations into the ethnicity-linked associations between maternal weight gain and prolonged labor are needed.
To address this potential association, the Japanese Society of Obstetrics and Gynecology (JSOG) Perinatal Committee recently issued recommendations on appropriate weight gain during pregnancy. To this end, excessive weight gain was defined as weight gain of 15, 13, 10, or five kg in women with pre-pregnancy body mass index (BMI) values less than 18.5 kg/m2, 18.5- 25 kg/m2, 25-30 kg/m2, and over 30.0 kg/m2, respectively. However, these recommendations have never been scientifically validated.
The present study aims to investigate the association between excessive weight gain and prolonged labor using the new JSOG recommendations. Data were obtained from the Japan Environment and Children’s Study (JECS), an ongoing Japanese birth control study conducted at 15 regional centers across Japan comprising women recruited between January 2011 and March 2014.
Study inclusion criteria included women with expected delivery dates after August 2011 with completed obstetric and demographic records. Women who delivered before 37 weeks of gestation, after 42 weeks of gestation, underwent Cesarean sections or had multiple pregnancies were excluded from the analysis.
Collected data included medical and obstetric records and participant-completed questionnaires during the first, second, and third trimesters and postpartum. Pregnancy weight gain was calculated by comparing maternal body weight before pregnancy and seven days before delivery. Confounding covariates included obesity, stature, large-for-gestational-age (LGA) infants, anesthesia, and maternal age.
Statistical analyses included the Student’s t-test and χ2 test for confounding variables analysis, multivariate logistic regressions for calculating odds ratios (ORs) and adjusted ORs (aORs), and Kaplan-Meier analysis to estimate the influence of maternal weight gain on labor duration.
Study findings
Of the 104,062 participants of the JECS cohort, 71,154 women met the study inclusion criteria. The mean maternal age was 30.9 years, with a mean BMI of 21.1 kg/m2.
The cohort comprised 28,442 nulliparous and 42,712 multiparous women. Using JSOG criteria, 15,996 women presented with excessive pregnancy weight gains, 82.9% of whom had pre-labor BMIs over 25 kg/m2.
Gestational age, pre-pregnancy BMI, pre-labor BMI, maternal height, and labor duration were significantly increased in the excessive maternal weight gain sub-cohort as compared to the non-excessive weight gain cohort. The overall incidence rate of prolonged labor was 10.2%, with a mean labor duration of 12.4 hours compared to the normal group’s 8.5 hours. Over 82% of women with prolonged labor had a pre-labor BMI exceeding 25 kg/m2.
Multivariate and Kaplan-Meier analyses established a statistically significant association between excessive maternal weight gain during pregnancy and the subsequent risk of prolonged labor for both nulliparous and multiparous women with aORs of 1.21 and 1.15, respectively.
Conclusions
In the present nationwide Japanese cohort, excessive maternal weight gain was significantly associated with prolonged labor. These findings are likely an underestimate of the true association between the estimated variables due to a large proportion of excluded cesarean section deliveries having been prolonged vaginal deliveries if more time had been taken.