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ORIGINAL RESEARCH |
From the Nurse-Midwifery Center and Department of Obstetrics and Gynecology, Milwaukee Clinical Campus, University of Wisconsin Medical School, Milwaukee, Wisconsin.
Address reprint requests to: Paul S. Kaiser, MSN, CNM Sinai Samaritan Medical Center Department of Obstetrics and Gynecology P.O. Box 342 Milwaukee, WI 53201-0342 E-mail: paulkcnm{at}aol.com
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Abstract |
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Methods: We studied 1881 women who delivered between 1994 and 1998 and were managed by an academic inner-city hospital-certified nurse-midwifery practice. We calculated prepregnancy BMI and weight gain during pregnancy by using clinical data from a comprehensive clinical database, and did descriptive analyses and univariate and multivariate logistic regression analyses.
Results: The overall cesarean rate was 5.1%, but was 7.7% for obese women compared with 4.1% for women with normal BMI (19.8–25.9). The unadjusted odds ratio (OR) for cesarean for obese women was 2.02 (95% confidence interval [CI] 1.26, 3.25, P < .01). Other factors associated with increased risk of cesarean delivery included primigravidity, primiparity, maternal age 35 years or older, short stature (height under 155 cm), very low birth weight infant, failure to progress, breech presentation, abruption, fetal bradycardia, and severe preeclampsia. Maternal race and marital status were not associated with cesarean delivery. After adjustment for weight gain, short stature, advanced maternal age, primiparity, and intrapartum complications, the OR for obesity was 3.99 (95% CI 2.00, 7.95, P < .001).
Conclusion: Even among low-risk women managed by nurse-midwives, the risk of cesarean delivery was higher for obese women. Short, obese women were at higher risk of cesarean delivery compared with women with normal BMIs, but were not high enough risk to preclude them from receiving nurse-midwifery care.
Much research shows the health risks of obesity, which cross all racial-ethnic and social strata, and poses a significant problem for black women, for whom the obesity rates can be twice as frequent as for white women.1,2 Maternal obesity associates with antenatal complications from diabetes and hypertension to postdatism, and with intrapartum complications including prolonged second stage of labor, increased need for oxytocin, macrosomia, shoulder dystocia, and higher cesarean delivery rates.3
Studies on perinatal outcomes of women who received care from certified nurse-midwives have shown similar or better results compared with those who received care from physicians. Those outcomes included lower cesarean rates, fewer low birth weight (LBW) infants, and lower neonatal mortality rates.4,5 Oakley et al6 reported a 19% cesarean delivery rate for a physician care group compared with 13% for a nurse-midwife care group, and a difference in operative delivery rates of 16% compared with 7% for physician and nurse-midwife groups, respectively. Davis et al7 found that women cared for by nurse-midwives had lower cesarean delivery rates, fewer interventions, and equally good maternal and infant outcomes compared with those cared for by physicians. Women served by nurse-midwifes tended to have lower health risks.6–8
Researchers have begun to use body mass index (BMI) to differentiate obese from nonobese individuals. Obese women (BMI above 29) have increased risk of cesarean delivery.9 Cnattingnius et al10 found that the effect of prepregnant BMI on cesarean delivery rate was influenced by maternal height. Tall, lean women had the lowest cesarean rate (5%), followed by tall, obese (11%), and short, lean women (19%), whereas short obese women had the highest rate (36%). Witter et al11 found that as prepregnant BMI or total weight gain for pregnancy increased, cesarean delivery risk increased linearly. However, they did not define a threshold for prepregnant BMI or total pregnancy weight gain above which cesarean rates increased rapidly.
We evaluated whether obese women who received prenatal care at nurse-midwifery clinics were at increased risk of cesarean delivery compared with women with normal prepregnant BMIs, and examined the effect of associated risk factors on cesarean delivery including pregnancy weight gain and maternal stature.
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Materials and Methods |
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Data for the nurse-midwife practice’s deliveries were entered into a comprehensive computerized database. One author (PSK) was responsible for collecting and abstracting all data from in-patient medical records and prenatal records for the database. The database contained maternal demographic characteristics; medical and obstetric histories; and antepartum, intrapartum, postpartum, and neonatal outcomes. When women had more than one pregnancy during the study, all were included. If data on maternal height or prepregnancy weight were missing, that case was removed from the study.
Prepregnant height and weight were self-reported at initial prenatal visits. Height was measured at the first prenatal visit if women were uncertain about it. Weight at first prenatal visit was selected as prepregnant weight if that value was uncertain or there was a large discrepancy and the woman was at less than 12 weeks’ gestation. Studies of self-reported height and weight have shown relatively small errors, with errors in self-reported weight increasing with degree of obesity.12 That introduced a potential bias to our analysis, but the average woman gains 2–4 lbs during the first trimester, so the overall effect of errors in attribution of prepregnancy weight is likely to be small.13
Total pregnancy weight gain was calculated by subtracting prepregnant weight from weight at last prenatal visit closest to delivery. We did not calculate that weight if there was a lapse in prenatal care longer than 3 weeks from the last prenatal visit to delivery.
The BMI was calculated using prepregnant weight. We classified BMI according to the Institute of Medicine categories: under 19.8 (lean), 19.8–26.0 (normal), 26.1–28.9 (overweight), and 29 or higher (obese). Total weight gain during pregnancy was classified according to the Institute of Medicine’s report on nutrition in pregnancy, modified to provide an upper limit for normal weight gain for obese women based on the study by Parker and Abrams (Table 1
).14,15 Each BMI group was evaluated separately for pregnancy weight gain compared with those recommendations. Among 2320 women who delivered from 1994–1998, 439 cases (18.9%) were removed because of missing height (n = 25), prepregnant weight (n = 19), or both (n = 395), leaving 1881 cases for analysis. An additional 93 subjects were removed because we were unable to calculate total weight gain. Analysis of population characteristics between cases studied and those removed showed some differences. Cases we were unable to analyze were more likely to be primiparas, nonblack, and slightly older than study subjects. There were three cesareans among 439 removed cases (0.7%).
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2 and t test for difference of means) and univariate and multivariate logistic regression. Univariate analysis of predictors of cesarean delivery included known risk factors (ie, birth weight less than 1500 g) and demographic, reproductive, and intrapartum measures. Multivariable logistic regression analysis was used to evaluate the association of cesarean delivery with various outcomes, controlling for potential confounding variables and race and marital status. Statistical analyses were done using the Statistical Analysis System (SAS 6.12; SAS Institute, Cary, NC). |
Results |
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. The racial and marital composition was largely black (77.1%) and single (90.6%), indicative of the general population served by the hospital. The mean maternal age was 21.1 years. There were 96 cesarean deliveries among 1881 subjects (5.1%). For obese women the rate was 7.7%, and for lean women 3.6% (Table 3), compared with a rate of 4.1% for average-weight women. The unadjusted odds ratio (OR) of cesarean delivery for obese women was 2.02 (95% confidence interval [CI] 1.26, 3.25; P < .01) compared with an OR of 0.90 (95% CI 0.43, 1.90; P > .05) for lean women (Table 4). Compared with 20–24-year-old women, there were no differences in unadjusted risk of cesarean delivery by age among women under age 35 years. Women 35 years or older were at increased risk of cesarean delivery (OR 3.61; 95% CI 1.31, 9.93; P < .02). Other factors associated with cesarean delivery included primigravidity (OR 1.53, 95% CI 1.02, 2.28; P < .04), primiparity (OR 2.69, 95% CI 1.75, 4.14; P < .001), and short stature (height under 155 cm, OR 2.45, 95% CI 1.41, 4.26; P < .001).
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Results of the multivariable analysis are shown in Table 5. After controlling for maternal race (black), marital status, primigravidity, very low birth weight, and all other factors in the table, the adjusted OR of cesarean delivery for obesity was 3.99 (95% CI 2.00, 7.95; P < .001). Maternal age 35 years or older, short stature, and weight gain greater than that recommended by the Institute of Medicine also independently increased the odds of cesarean delivery.
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. In the overweight group, 70.0% had weight gain in excess of recommendation, whereas 72.1% of the obese group were within the recommended range as modified for this study.
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Discussion |
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Our results suggest that even among low-risk women managed by nurse-midwives, the risk of cesarean delivery is three to four times higher if they are obese, which does not make obese women inappropriate for prenatal management by nurse-midwives. Even with the increased risk, this inner-city population had an overall cesarean rate of 5.1% and 7.7% for obese women. Those rates are far below the Healthy People 20001 recommended goal for cesarean births. Obesity in the study population (24%) was similar to findings by Crane et al9 (18.2%), but outcomes were very different (7.7% compared with 33.8% cesarean delivery rates).
We concur with the findings of Cnattingius et al10 of increased risk of cesarean delivery for short, obese women. There was no association between maternal age and cesarean delivery for women under 35 years old. Compared with 20–24-year-old women, those 35 or older had a threefold greater likelihood of cesarean delivery. After controlling for all factors studied (Table 5
), older maternal age increased the likelihood of cesarean delivery more than fivefold.
In 1990, the Institute of Medicine established recommended pregnancy weight gain ranges for underweight, normal, and overweight women. For obese women, they set a minimum level to gain of 15 lb but made no upper range limit. Several studies14,17,18 recommended a weight gain range of 15–37 lb for women with BMIs above 29. Women who gain less than the lower limit are at increased risk of having small for gestational age infants. Women with weight gains beyond the upper limits for their BMIs are at increased risk of having large for gestational age infants and cesarean delivery. Frentzen et al19 suggested that no minimum weight gain be required for women whose degree of obesity is at or above 135% of standard body weight for height. Pregnancy weight gain was associated with birth weight in the average weight groups but did not significantly affect birth weight in the obese group. Neither Hickey et al20 nor Schieve et al21 found support for race-specific prenatal weight gain recommendations. However, it is difficult to compare results of pregnancy weight gain studies. Some researchers used the Metropolitan Life Insurance height and weight tables, whereas others used prepregnant weight greater than 200 lb (90 kg), regardless of maternal height, as the definition of obesity. Still other studies defined it as weight of 50–300% greater than ideal weight for height. There is general agreement that normal weight for height is a BMI of 20–26, but studies are inconsistent in their definitions of obesity. With BMI alone, it is not possible to differentiate between lean muscle and total body fat.
After controlling for other factors, we found that pregnancy weight gain above the Institute of Medicine’s recommendations was associated with an almost twofold increase in adjusted risk of cesarean delivery. The Institute did not establish an upper limit for pregnancy weight gain in obese women, so it was necessary to use other studies to establish an upper limit for obese women to study the effect of excessive gains. We used the limits defined by Parker and Abrams.14 The upper limit of normal weight gain for obesity might have been set too high. Further studies are needed to establish an appropriate upper limit for recommended weight gain for women with BMIs above 29 during pregnancy.
We found that as BMI increased, the proportion of women with below-recommended weight gain or loss decreased, although obese women were more likely than overweight women to have weight gain below the recommendations. Patient height is not modifiable, but obstetric care providers should focus on preconception nutrition and anthropometrics. Body mass index–specific pregnancy weight gain objectives should be managed expectantly by prenatal care providers, including dietitians for nutritional support, early testing for gestational diabetes, and ultrasound to monitor fetal growth.
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Footnotes |
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Received January 3, 2000. Received in revised form July 6, 2000. Accepted September 7, 2000.
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References |
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2. Kuczmarski RJ, Flegal KM, Campbell SM, Johnson CL. Increasing prevalence of overweight among US adults. The National Health and Nutrition Examination Surveys, 1960 to 1991. JAMA 1994;272: 205–11.[Abstract]
3. Ekblad U, Grenman S. Maternal weight, weight gain during pregnancy and pregnancy outcome. Int J Gynaecol Obstet 1992;39: 277–83.[Medline]
4. Butler J, Abrams B, Parker J, Roberts JM, Laros RK Jr. Supportive nurse-midwife care is associated with a reduced incidence of cesarean section. Am J Obstet Gynecol 1993;168:1407–13.[Medline]
5. Chambliss LR, Daly C, Medearis AL, Ames M, Kayne M, Paul R. The role of selection bias in comparing cesarean birth rates between physician and midwifery management. Obstet Gynecol 1992;80:161–5.
6. Oakley D, Murray ME, Murtland T, Hayashi R, Andersen HF, Mayes F, et al. Comparisons of outcomes of maternity care by obstetricians and certified nurse-midwives. Obstet Gynecol 1996; 88:823–9.[Abstract]
7. Davis LG, Riedmann GL, Sapiro M, Minogue JP, Kazer RR. Cesarean section rates in low-risk private patients managed by certified nurse-midwives and obstetricians. J Nurse-Midwifery 1994;39:91–7.[Medline]
8. MacDorman MF, Singh GK. Midwifery care, social and medical risk factors, and birth outcomes in the USA. J Epidemiol Community Health 1998;52:310–7.[Abstract]
9. Crane SS, Wojtowycz MA, Dye TD, Aubry RH, Artal R. Association between pre-pregnancy obesity and the risk of cesarean delivery. Obstet Gynecol 1997;89:213–6.[Abstract]
10. Cnattingius R, Cnattingius S, Notzon FC. Obstacles to reducing cesarean rates in a low-cesarean setting: The effect of maternal age, height, and weight. Obstet Gynecol 1998;92:501–6.[Abstract]
11. Witter FR, Caulfield LE, Stoltzfus RJ. Influence of maternal anthropometric status and birth weight on the risk of cesarean delivery. Obstet Gynecol 1995;85:947–51.[Abstract]
12. Lederman SA, Paxton A. Maternal reporting of prepregnancy weight and birth outcome: Consistency and completeness compared with the clinical record. Matern Child Health J 1998;2:123–6.[Medline]
13. Abrams B. Maternal nutrition. In: Creasy RK, Resnik R, eds. Maternal Fetal Medicine: Principles and Practice. 2nd ed. Philadelphia: WB Saunders, 1994:162–70.
14. Parker JD, Abrams B. Prenatal weight gain advice: An examination of the recent prenatal weight gain recommendations of the Institute of Medicine. Obstet Gynecol 1992;79:664–9.
15. Institute of Medicine. Nutrition during pregnancy and lactation. An implementation guide. Washington, DC: National Academy Press, 1992.
16. Rates of cesarean delivery—United States, 1993. MMWR Morb Mortal Wkly Rep 1995;44:303–7.[Medline]
17. Cogswell ME, Serdula MK, Hungerford DW, Yip R. Gestational weight gain among average-weight and overweight women—what is excessive? Am J Obstet Gynecol 1995;172:705–12.[Medline]
18. Edwards LE, Hellerstedt WL, Alton IR, Story M, Himes JH. Pregnancy complications and birth outcomes in obese and normal-weight women: Effects of gestational weight change. Obstet Gynecol 1996;87:389–94.[Abstract]
19. Frentzen BH, Dimperio DL, Cruz AC. Maternal weight gain: Effect on infant birth weight among overweight and average-weight low-income women. Am J Obstet Gynecol 1988;159:1114–7.[Medline]
20. Hickey CA, McNeal SF, Menefee L, Ivey S. Prenatal weight gain within upper and lower recommended ranges: Effect on birth weight of black and white infants. Obstet Gynecol 1997;90:489–94.[Abstract]
21. Schieve LA, Cogswell ME, Scanlon KS. An empiric evaluation of the Institute of Medicine’s pregnancy weight gain guidelines by race. Obstet Gynecol 1998;91:878–84.[Abstract]
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