|Year : 2015 | Volume
| Issue : 4 | Page : 858-863
Effect of obesity on the length of the first and second stages of labor
Mohamed Samy1, Zakaria F Sanad1, Mohamed A Emara1, Shrouk A Mohamed Abdou MBBCh 2
1 Department of Obstetrics and Gynecology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Nabarouh Central Hospital, Dakahlia, Egypt
|Date of Submission||02-Dec-2014|
|Date of Acceptance||08-Feb-2015|
|Date of Web Publication||12-Jan-2016|
Shrouk A Mohamed Abdou
El-Semad City, Talkha, Dakahlia, 35717
Source of Support: None, Conflict of Interest: None
This study was designed to evaluate the length of the first and second stages of labor in nulliparous obese Egyptian women and compare them with those in women with normal BMI.
Maternal obesity is now the most common risk factor for maternal mortality in developed countries and is also associated with a wide spectrum of adverse pregnancy outcomes. The duration of first stage of labor, the rate of cesarean delivery, and inadequate progress of cervical dilatation during labor were found to be higher in women with BMI more than 30 compared with women of average weight.
Participants and methods
Nulliparous women of more than 37 gestational weeks who were in labor were included in this study. First-visit BMI was used to categorize weight as normal (≤24) or obese (≥30). Over 12 months (study period), we observed 603 deliveries; 239 were nulliparous and 211 were term singleton. Eighty women met the inclusion criteria: 40 women with normal BMI constituting the control group and 40 obese women who constituted the study group.
The duration of first stage of labor was significantly longer in obese women compared with normal weight women (19.76 ± 0.77 vs. 16.87 ± 0.66 h; P < 0.001), whereas the duration of the second stage of labor showed no significant difference between obese and normal weight women (61.0 ± 34.8 vs. 60.9 ± 34.3 min; P = 0.990). When adjusted for age, hypertension, and induction, the likelihood of completing stages I and II was significantly lower among obese nulliparous than among those with BMI 24 or less.
About half of nulliparous women in our population are obese and the duration of stage I is significantly longer among them, whereas the second stage of labor may be independent of maternal BMI. The second stage in the nulliparous parturient woman does not appear to be longer or more likely to end in cesarean delivery on the basis of prepregnancy BMI
Keywords: BMI, first stage, labor, obesity, second stage
|How to cite this article:|
Samy M, Sanad ZF, Emara MA, Mohamed Abdou SA. Effect of obesity on the length of the first and second stages of labor. Menoufia Med J 2015;28:858-63
|How to cite this URL:|
Samy M, Sanad ZF, Emara MA, Mohamed Abdou SA. Effect of obesity on the length of the first and second stages of labor. Menoufia Med J [serial online] 2015 [cited 2020 Jun 1];28:858-63. Available from: http://www.mmj.eg.net/text.asp?2015/28/4/858/173604
| Introduction|| |
The prevalence of obesity is increasing worldwide and this trend also affects women of reproductive age. Maternal obesity is now the most common risk factor for maternal mortality in developed countries and is also associated with a wide spectrum of adverse pregnancy outcomes  .
In the longer term, obesity and excessive weight gain during pregnancy are associated with increased risks for cardiovascular and metabolic diseases for the mother and with increased risks for obesity in the offspring , .
Gestational diabetes, hypertension, preeclampsia, macrosomia, induction of labor, cesarean delivery, postpartum hemorrhage, post-term pregnancy, preterm pregnancy, genital infection, urinary infection, wound infection, intrauterine fetal death, neonatal death, long hospitalization, birth defects, low Apgar score, neural tube defects, thromboembolic events, neonatal icterus, anemia, varicosity, and shoulder dystocia are some of the complications indicated , .
Some studies reported an increase in some of the above, which may indicate the consequence of obesity and high maternal weight  .
The impact of high maternal weight on labor is the subject of several studies, with varying results. One study reported no important difference in basal uterine contractility between overweight women and those of normal weight, but in women with BMI more than 25 the need for oxytocin during labor, as well as the duration of labor, including the active phase of labor, was higher than in patients of normal weight  .
Another study on the rate of cesarean delivery due to prolongation of first stage of labor found the incidence of cesarean delivery to be higher in overweight and obese women even if the neonatal weights were the same. The study also found that uterine contractility and frequency of contractions and increased ionized calcium (Ca +2 ) flux during labor in obese women were less than in normal weight women  .
The duration of first stage of labor, the rate of cesarean delivery, and inadequate progress of cervical dilatation during labor were found to be higher in women with BMI more than 30 compared with women of average weight. In contrast, another study revealed that there was no difference in the duration of labor or delivery method in normal and obese women  .
Studies on the characteristics of labor in obese gravid women have been limited. We are aware of only two studies that examined the duration of second stage in a nulliparous population categorized by BMI. Obesity was associated with a shorter second stage, compared with normal weight, in one study, whereas the other study demonstrated no difference in the duration of second stage between obese and normal weight participants , .
This study was designed to evaluate the length of the first and second stages of labor in nulliparous obese Egyptian women and compare them with women of normal BMI.
| Participants and methods|| |
This study included 40 nulliparous women aged 20-36 years at more than 37 gestational weeks who were in labor, along with 40 normal women who served as controls. They were selected from Bab El Shearia Hospital, Al-Azhar University, during the period from May 2012 to May 2013.
The inclusion criteria:
- The women had to be either obese (BMI≥30), to constitute the study group, or of normal weight (BMI≤24), to constitute the control group;
- They had to be nulliparous, with a singleton pregnancy of a reliable gestational age of at least 37 weeks, and in spontaneous labor.
The women were subjected to at least four digital examinations to allow us to better describe labor progression with sufficient data.
The exclusion criteria:
- BMI ranging between 25 and 29.9, or less than 18.5 (women with BMI between 18.5 and 24.9 were considered as the control group);
- Multiple gestations;
- Contraindications to vaginal delivery;
- Women enrolled initially but who delivered subsequently by cesarean section;
- Incidence of placental abruption;
- Presence of maternal heart disease; and
- Major fetal malformation.
All participants gave written consent after detailed explanation of the purpose of the study through a well-designed structured questionnaire; full data were collected from eligible patients, including detailed personal, menstrual, and obstetric history. BMI was calculated by dividing body weight in kg by height in m 2 . Approval was obtained from the ethical committee for performing the study.
Women were classified into two groups:
- Group I (control group): This group comprised 40 women with BMI ranging between 18.5 and 24.9.
- Group II (case group): This comprised 40 women with BMI equal to or more than 30.
The primary endpoints of the study were the following:
- The length of stage I labor, defined as the time from onset of active phase of labor until full cervical dilatation. After admission, women were monitored from the start of uterine contractions. The optimum rate of uterine contractions considered was 3-4/10 min. Amniotomy was performed when the cervix reached 4 cm dilatation. When augmentation was needed, no prostaglandins were used. Oxytocin was given by intravenous drip infusion at 2.5 mU/min (prepared by adding 1 U/l, infused at the rate of 40 drops/min).
- Length of the second stage of labor, defined from full cervical dilatation until expulsion of the fetus. Full cervical dilatation was confirmed by local vaginal examination and when the subjects started to bear down involuntarily.
Secondary outcome parameters included the occurrence of chorioamnionitis, third-degree or fourth-degree perineal tears, postpartum hemorrhage, or neonatal morbidity and mortality.
Data were collected and tabulated according to standard statistical methods. Demographic data and primary and secondary outcomes of both groups were compared using the t-test (for quantitative measures), the log-rank test, the c2 -test, and Fischer's exact tests (for categorical measures). A P value less than 0.05 was considered statistically significant.
| Results|| |
Over the 12-month (from May 2012 to May 2013) study period, there were 603 deliveries in Bab El Shearia Hospital, Al-Azhar University; of these, 60% (n = 364) were in parous women and 40% (n = 239) in nulliparous women. The rate of delivery before 37 weeks among nulliparous women was 12% (n = 28). Among the 211 term nulliparous pregnancies, 62% (n = 131) were excluded for reasons such as elective cesarean delivery before onset of labor, insufficient cervical exams, late prenatal care, or cesarean section after attempting vaginal delivery.
[Table 1] shows comparison between the two groups as regards age (years); the age of the women in the study group ranged from 20 to 36 years, with a mean of 28 ± 8 years, with statistically nonsignificant difference from the control group (P = 0.934).
|Table 1 Comparison between case and control groups as regards age (years)|
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[Table 2] and [Table 3] show that the two groups differed significantly with respect to hypertension, diabetes, asthma, and augmentation induction rate (P = 0.003, 0.023, 0.157, and 0.141, respectively).
|Table 2 Comparison between case and control groups as regards hypertension, diabetes, and asthma|
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|Table 3 Population characteristics as regards spontaneous and augmentation/induction|
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[Table 4] shows that there was no significant difference between the two groups as regards gestational age at delivery (weeks) and excessive gestational weight gain (P = 0.684, 0.057).
|Table 4 Gestational age at delivery (weeks) and excessive gestational weight gain|
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[Table 5] shows the duration of different stages of labor in the two groups. Obese women spent a median of about 17 h in the first stage of labor versus about 20 h for normal weight women ([Figure 1]). The measurement of the second stage of labor and the total duration of labor were not significantly different between the two groups ([Figure 2]). The mean duration of the third stage of labor was not significantly different between the two groups on the basis of parity, interval from previous pregnancy, maternal weight gain, and rupture of the membrane at the time of admission, but it was longer in the study group in which oxytocin had been used.
[Table 6] shows that there were no significant differences between the two groups as regards birth weight (g) (<2500, P = 0.571; 34000, P = 0.074).
Duration of stage I labor was compared among women with various complications, including those with augmented or induced labor. Induction and hypertensive disease were associated with significantly longer stage I but not maternal age, diabetes, asthma, and birth weight ([Table 7]).
[Table 8] displays the median duration of the second stage, expressed in hours and classified by BMI (P = 0.99).
Induction of labor is a commonly recognized risk factor for cesarean delivery and prolonged labor. Because of a higher frequency of labor induction within this cohort of obese women compared with their normal weight counterparts, the data were analyzed to determine whether the relationship between BMI and duration of second stage of labor differed between those with induced and those with spontaneous labor. The relationship between BMI and second-stage duration did not differ between women with induced and those with spontaneous labor.
| Discussion|| |
Obese women have multiple complications during the peripartum period, including a higher rate of cesarean delivery. If the BMI is 30 or more, the rate of cesarean delivery is higher  .
Others have noted that even if comorbidities such as hypertension and diabetes are excluded, obese women are more likely to have abdominal delivery  , although several studies have noted a higher likelihood of failure to progress necessitating cesarean delivery , .
There are many findings in this prospective study. First, in our population at the start of pregnancy one of three was obese. Compared with other studies, the likelihood of obesity appears to be higher in our population, our statistics corresponding to those of Vahratian et al.  .
As most women do not lose the weight gained during pregnancy, it is expected that most of the nulliparous women in our population will have a BMI greater than 25 in subsequent pregnancies, which will increase the likelihood of complications  .
The second finding was that, as the BMI increases, so does the likelihood of diabetes, hypertension, induction, cesarean delivery, and macrosomia. These complications are consistent with earlier publications and ACOG committee opinion.
For example, some studies reported that, compared with women of normal weight, obese nulliparous women are significantly more likely to have comorbidity (diabetes, hypertension), cesarean delivery, and newborns with weight over 4000 g , .
The third finding is that BMI influences stage I of labor but not stage II. The duration of stage I differs significantly among obese and normal weight women. Even when adjusted for confounding variables, obese women are 27% less likely to reach the second stage of labor than women with a normal BMI.
The fourth finding is that there was no association between maternal BMI and length of the second stage in nulliparous women. In addition, maternal BMI in nulliparous women reaching the second stage is not associated with a higher incidence of cesarean delivery.
A retrospective case-control study including 51 obese nulliparous women (BMI>35) and 60 nulliparous normal weight controls (BMI < 26) in spontaneous labor found no difference in the duration of second stage of labor  .
Another prospective cohort study that included 71 women during the second stage of labor determined that second-stage duration between obese women and nonobese controls was similar. They also found no increase in the frequency of operative delivery or perineal lacerations  .
To the contrary, the Vahratian et al.'s  study, which included 612 participants, found that obese nulliparous women had a shorter second stage of labor compared with normal weight controls, contradicting the theoretical notion that soft tissue dystocia may lead to longer labors in obese women.
Our study supports the findings of Verdiales et al.  , and Buhimschi et al.  , in that we found no evidence of increased second-stage duration in women with increasing BMI, nor did we find an association between BMI and cesarean delivery in women reaching the second stage.
Our results mirror those of Robinson et al.  in that increasing BMI appears to be a risk factor for cesarean delivery in the first stage but not in the second stage of labor.
Finally, we grouped women with induced, augmented, and spontaneous labor together. Even though labor was significantly longer for women who were augmented or induced, we were able to control for this variable, and obesity was still a significant risk factor for not completing the first stage of labor  .
| Conclusion|| |
In conclusion, over one-third of nulliparous women in our population are obese, and the duration of stage I is significantly longer among them. Prospective studies are needed to determine the optimum time intervals for cervical dilation in active phase of labor in obese women.
These data suggest that the characteristics of the second stage of labor may be independent of maternal BMI. The second stage in the nulliparous parturient woman does not appear to be longer or more likely to end in cesarean delivery on the basis of prepregnancy BMI. This knowledge may aid obstetric providers in counseling women about the expected effect of their BMI on their intrapartum course, as well as assist in clinical decision making in women who reach the second stage of labor.
Studies should be conducted to detect the relationship between obesity and cervical effacement, fetal assessment, fetal outcome, and mode of delivery.
| Acknowledgements|| |
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]