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Obesity in Pregnancy
1. Obesity in
Pregnancy
Healthy Mothers, Healthy
Babies Coalition
Conference
October 7, 2015
Nicole S. Carlson, CNM, PhD Candidate
NIH NINR Grant # March of Dimes
2. Objectives
• Review scope of obesity epidemic in U.S.
• Review the influence of obesity on outcomes for both
mother and baby in pregnancy.
• Review the incidence and sequelae of unplanned
cesarean among obese women.
• Review the influence of increased BMI on patterns of
labor progress.
• Provide discussion of the use of common intrapartal
interventions with obese women.
• Review evidence-based recommendations for pre-conceptual,
antepartal, and postpartum care of obese
woman.
3. Obesity Epidemic in U.S.
• Obesity epidemic
– Dramatic increase from 1990-2010
• Obesity disproportionate among racial/ethnic minorities in U.S.1
199
0
2000 2010
• Cesarean delivery among obese women associated with poor outcomes
– Post-op infection, clotting disorder, hemorrhage, prolonged hospitalization
– 1/3 of maternal deaths associated with obesity complications, many following cesarean delivery2
1Flegal et al, 2012
2Grundy et al, 2008
33.4% obese
(95% CI 30.3-36.6)
40.7% obese
(95% CI 36.7-44.8)
58.6% obese
(95% CI 52.5-64.5)
CDC
No Data <10% 10%–14% 15%–19% 20%–24% 25%–29% ≥30%
5. Obesity in Women
2/3 of U.S. women of childbearing age are
obese or overweight1
1Flegal, et al (2012). Prevalence of obesity and trends in the distribution of body mass index
among US adults, 1999-2010. JAMA, 307(5), 491-497.
6. Racial Disproportions of Obesity
• Obesity disproportionate among racial/ethnic minorities in U.S.1
• Cesarean delivery among obese women associated with poor outcomes
– Post-op infection, clotting disorder, hemorrhage, prolonged hospitalization
– 1/3 of maternal deaths associated with obesity complications, many following cesarean delivery2
1Flegal et al, 2012
2Grundy et al, 2008
33.4% obese
(95% CI 30.3-36.6)
40.7% obese
(95% CI 36.7-44.8)
58.6% obese
(95% CI 52.5-64.5)
Flegal et al, 2012
7. Maternal Obesity: Multiple Risks for
Mom & Baby in Pregnancy
Risks to Obese Woman1
• depression & anxiety4
– depression pregnancy OR 1.43 (1.27-1.61)
– PPD OR 1.30 (1.20-1.42)
– Anxiety OR 1.41 (1.10-1.80)
• GDM
– increase by 0.82% with each 1kg/m2 increase
BMI (3.76X increase on avg)
• gestational HTN
– 2.5-3.2 OR
• pre-eclampsia
– Double risk with each increase 5-7 kg/m2 in
BMI
• prolonged pregnancy
– Double risk (>41wk)
Risks to Baby
• risk congenital anomalies, neural
tube defects especially2
• 2-to 3-fold increase macrosomia1
• lifetime risk of DM, heart
disease, obesity2
• 2 fold risk IUFD in late 3rd trimester1
• 1.5-2 fold increase in risk of
spontaneous extremely preterm
delivery (22-27wks), dose-dependent
by BMI3
• 1.5-2.7 fold increased risk of
induced preterm delivery, dose-dependent
by BMI3
1Mission, J. F., et al (2013). Obesity in pregnancy: a big problem and getting bigger. Obstet Gynecol Surv, 68(5), 389-399.
2O'Reilly, J. R., & Reynolds, R. M. (2013). The risk of maternal obesity to the long-term health of the offspring. Clin Endocrinol (Oxf), 78(1), 9-16.
3Cnattingius, et al (2013). Maternal obesity and risk of preterm delivery. JAMA, 309(22), 2362-2370.
4Molyneaux et al, 2014. Obesity and mental disorders during pregnancy and postpartum: a systematic review and meta-analysis. Obstet & Gynec
123(4), 857-867.
9. Preconception
• Contraception
US Medical Eligibility Criteria:
Categories
1
No restriction for the use of the contraceptive method
for a woman with that medical condition
2
Advantages of using the method generally outweigh
the theoretical or proven risks
3
Theoretical or proven risks of the method usually
outweigh the advantages – or that there are no other
methods that are available or acceptable to the
women with that medical condition
4
Unacceptable health risk if the contraceptive method
is used by a woman with that medical condition
http://www.cdc.gov/mmw r/pdf/rr/rr5904.pdf
10. Bariatric Surgery
• Most effective weight loss treatment for morbid obesity
• Incidence increased 800% from 1998-2005
• Women account for 83% of procedures among reproductive age
• Generally available to women with BMI >40 or BMI >35 with
comorbidities
• Types of Surgery –
• Restrictive Procedures (i.e., lap band/sleeve)
• Decreases stomach capacity
• Malabsorptive Procedures (i.e., Roux-en-Y gastric bypass)
• Decreases absorption of calories & nutrients by shortening functional
length of small intestine
• Bariatric Surgery and Pregnancy. ACOG Practice Bulletin No. 105. American College of Obstetricsians and Gynecologists. Obstet Gynecol 2009;113:1405-
13.
11. Effect of Surgery on Fertility
• Rapid weight loss follows bariatric surgery
• Improves PCOS, anovulation, irregular menses
• Results in higher fertility rates
• Avoid pregnancy for 12-24 months after
surgery
• Patient allowed to achieve full weight loss
• Fetus not exposed to rapid maternal weight
loss environment
– Paulen, ME et al. Contraceptive use among women with a history of bariatric surgery: a systematic review. Contraception 82
(2010) 86-94.
13. IOM Guidelines (2009)
Balance risks of having LGA infants, SGA infants, preterm births,
and postpartum weight retention
Pre-pregnancy weight category BMI Recommended total
weight gain
Recommended rate of
weight gain in the 2nd/3rd
trimesters
Underweight < 18.5 28-40 lbs 1 lb (1-1.3)
Normal 18.5 – 24.9 25-35 lbs 1 lb (0.8-1)
Overweight 25 – 29.9 15-25 lbs 0.6 lbs (0.5-
0.7)
Obese (includes all classes)
Class I: BMI 30-34.9
Class II: BMI 35-39.9
Class III: BMI >40
> 30 11-20 lbs 0.5 lbs (0.4-
0.6)
14. Gestational Weight Gain
gestational weight gain associated with risk of C-section, HTN, GDM
15. Early Pregnancy
• Height/weight and calculate BMI at 1st visit
• Ultrasound in 1st tri to confirm dates (ovulatory dysfxn common in obese women)
• Aneuploidy Screening 1st trimester options (sequential screen, NT US, NIPT)
• Depression & Anxiety screeningNOB, 28 weeks, and in 3rd trimester
• Risk factor identification
• Risk HTN d/o’s Baseline PET labs before 20 wks
• Risk GDM A1c to screen for pre-existing DM and 2hr GTT at 24 wks
• Nutritional counseling & explicit weight gain recommendations*
• Exercise encouragement & recommendations*
• Detailed fetal anatomy scan 16-20wks (earlier GA if class III obesity) with explanation of
limitations
• Frequent visits in 3rd trimester for assessment of fetal growth + maternal heath (BP
measurements, weight gain, OSA sx’s, orthopedic difficulties)
• Strong evidence does not exist for timing of delivery and/or antenatal surveillance
16. Nutrition & Exercise
• Offer nutrition consultation
• Consider having patients plot their own weight on charts
• Additional folic acid for all obese women (4mg/day starting 2 mo prior conception thru
1st trimester)
• Nutritional considerations for women who have had a bariatric procedure
• Risk for protein, iron, vit B12, folate, vit D, calcium deficiencies
• Supplement if deficient
• Monitor CBC, iron, ferritin, calcium, vit D q trimester
• Treatment of Obese Pregnant Women (TOP) Study Renault KM, Norgaard K, Nilas L et al. The Treatment of Obese Pregnant Women (TOP) Study: a
randomized controlled trial of the effect of physical activity intervention assessed by pedometer with or without dietary intervention in obese pregnant women. Am J Obstet Gynecol 2014;210:134.e1-9.
• RCT 425 obese pregnant women in Denmark
• Goal < 5kg TWG
• physical activity (pedometer – daily step count 11,000)
• physical activity + diet (1200-1575kcal Mediterranean-style, nutrition f/u q 2 weeks)
• control group w/ standard care
• Gestational weight gain lower in 2 intervention groups
• No difference in neo birthweights among 3 groups (TWG < 5kg did not result in SGA
infants)
• Lower rate of emergency Cesarean delivery in physical activity + diet group
18. Obesity & Cesarean Delivery
Several meta-analysis examining link between maternal BMI & cesarean delivery.
• Chu et al, 2007. Maternal obesity and risk of cesarean delivery: a meta-analysis. Obesity Reviews, 8(5), 385-394.
– N=33 cohort studies, include all parities, include co-morbidities.
• Poobolan et al, 2008. Obesity as an independent risk factor for elective and emergency caesarean delivery in
nulliparous women – systematic review and meta‐analysis of cohort studies. Obesity Reviews, 10(1), 28-35.
– N=11 cohort studies, only nulliparous women, no co-morbidities, unplanned
cesarean delivery.
Odds Ratios for Cesarean Delivery (95% Confidence Intervals)
Study Normal
weight
BMI 20-25
Overweight
BMI 25-29
Obese
BMI 30-35
Very Obese
(BMI >35)
Chu 07 1 1.46(1.34-1.60) 2.05 (1.86-2.27) 2.89 (2.28-
3.79)
Poobolan
08
1 1.64 (1.55-1.73) 2.23 (2.07-2.42)
19. Dose-Dependent Association Obesity
& Cesarean Delivery
Kominiarek, et al 2011
• N=118,978 women, multi-site U.S.
• Consortium of Safe Labor
5% increase in risk of unplanned
cesarean with each increase in
BMI of 1 kg/m2
1Kominiarek et al, 2010. The maternal body mass index: a strong association with delivery route. Am J Obstet Gynecol, 203(3), 264 e261-267.
20. So What…Outcomes of Cesarean
Delivery Among Obese Women
Cesarean delivery among obese women associated with poor
outcomes:
• Wound infection/breakdown
• clotting disorder (VTE)
• hemorrhage
• prolonged hospitalization
• Endometritis
• Respiratory/airway complications
o 2-4X increased risk of post-op complications in women with BMI>45
o Primary infectious outcome
o Would infection
o Emergency department visit
o 1/3 of maternal deaths associated with obesity complications,
many following cesarean delivery2
Flegal et al, 2012
Obesity in Pregnancy. Committee Opinion No. 549. American College of Obstetricians and Gynecologists. Obstet Gynecol 2013:121;213-7.
21. Obesity & Cesarean Delivery
Dose-dependent association with
unplanned cesarean delivery
Primarily linked to
Kominiarek et al, 2011. Contemporary labor patterns: the impact of maternal body mass index.
American Journal of Obstetrics and Gynecology, 205(3), 244.e241-244.e248.
22. Abnormally slow progress during active phase labor
resulting from abnormalities in…1
Passage
Passenger
Power
1ACOG, 2003
Labor Dystocia
23. Abnormally slow progress during active phase labor
resulting from abnormalities in…1
Passenger
Power
2Crane et al, 1997. Association between pre-pregnancy obesity and the risk of cesarean delivery. Obstetrics and Gynecology, 89(2), 213-216.
3Fyfe et al, 2011. Risk of first-stage and second-stage cesarean delivery by maternal body mass index among nulliparous women in labor at
term. Obstet Gynecol, 117(6), 1315-1322.
4Kominiarek et al, 2011. Contemporary labor patterns: the impact of maternal body mass index. American Journal of Obstetrics and
Gynecology, 205(3), 244.e241-244.e248.
Labor Dystocia
24. Labor Dystocia
Abnormally slow progress during active phase labor
resulting from abnormalities in…
Power
Verdiales, 2009. The effect of maternal obesity on the course of labor. Journal of Perinatal Medicine, 37(6), 651-655.
25. Labor Dystocia
Abnormally slow progress during active phase labor
resulting from abnormalities in…
Zhang et al, 2007. Contractility and calcium signaling of human myometrium are profoundly affected by cholesterol
manipulation: implications for labor? Reprod Sci, 14(5), 456-466.
Cedergren, 2010. Non-elective caesarean delivery due to ineffective uterine contractility or due to obstructed labour in relation
to maternal body mass index. Eur J Obstet Gynecol Reprod Biol, 145(2), 163-166.
26. Leptin & Cholesterol in Obese Women
Leptin
• Elevated in obese women
• Produced by fat cells
• Also produced by placenta
• In obesity, leptin resistance
Tessier, D. R., Ferraro, Z. M., & Gruslin, A. (2013). Role of leptin in
pregnancy: consequences of maternal obesity. Placenta, 34(3), 205-
211.
Cholesterol
• Elevated in obese women
• Positive association with
BMI, especially in people
between 25-35 years of age
Gostynski, M., et al. (2004). Analysis of the relationship between total
cholesterol, age, body mass index among males and females in the
WHO MONICA Project. Int J Obes Relat Metab Disords, 28(8), 1082-
1090
27. BIOLOGY OF OBESITY IN
PREGNANCY (4 MODELS)
Cholesterol causes disrupted contractility in
uterus
Smith et al, 2005
28. MODEL 2
Leptin disrupts contractility &
cervical/uterine ripening.
Wendremaire et al, 2012
From Moynihan et al, 2006
29. Garabedian et al, 2011; Elmes et al, 2011
MODEL 3
Decreased oxytocin receptors &
Connexin-43 connections
between myocytes.
30. Electrophysiologic Model of Uterus
with Irregular Propagation
Aslanidi, et al (2011). Towards a computational reconstruction of the electrodynamics of premature and full term human labour.
Prog Biophys Mol Biol, 107(1), 183-192.
31. Intrapartum Care of Obese Women
• Intrapartum intervention choices &
timing explain much of the
association between obesity &
unplanned cesarean delivery1
• Optimal intrapartum care lowered
rate of unplanned cesarean in
mixed weight group,
.2
1Abenhaim & Benjamin, 2011. Higher cesarean section rates in
women with high body mass index: are we managing
differently? J Obstet Gynaecology Canada, 33(5), 443-448.
2Leeman & Leeman, 2003. A Native American Community with
a 7% Cesarean Delivery Rate: Does Case Mix, Ethnicity, or
Labor Management Explain the Low Rate? The Annals of
Family Medicine, 1(1), 36 -43.
32. Intrapartum Interventions in the U.S.
FREQUENTLY INVOLVES HIGH-TECHNOLOGY
INTERVENTIONS, USED WITH
TIMING/INDICATION AGAINST EVIDENCE-BASED
GUIDELINES1
1Declercq et al, 2013.
33. Listening to Mothers Survey III
(n=2400 women)
High-Technology Intervention
in Labor
Intervention
No
Intervention
How Many Interventions in
Labor?
3 or more
interventions
1-2
interventions
Declercq et al, 2013
34. Intrapartum Interventions Associated with
Cesarean in Mixed-Weight Groups of Women
1Jackson, 2003
2Smyth et al, 2013
3Nguyen et al, 2009
4Dunne et al, 2009
5Debiec et al, 2009
35. Intrapartum Interventions in the
Labors of
SYSTEMATIC REVIEW OF THE LITERATURE, N=8 STUDIES:
Obese Women more often receive intrapartum
interventions including:
Induction of labor
Early Hospital Admission
AROM
Augmentation of labor
Epidural
Unplanned Cesarean Delivery
When compared to normal BMI referent
Carlson & Lowe, 2014 Intrapartum management associated with obesity in
nulliparous women. J Midwifery Womens Health, 59(1), 43-53 .
37. Induction of Labor in Obese Women
• Takes longer than spontaneous labor (which is already LONG)
• Labor duration & progress inversely related to maternal weight
• Failure to respond to prostaglandin cervical ripening
– 54.7% failure among obese
– 34.5% failure among normal wt women, p=.0016
– Up to 80% failure of induction rate among Obese III women who had
macrosomic fetus & no previous vaginal delivery2
1Gauthieret al 2011. Obesity and cervical ripening failure risk. Journal of Maternal-Fetal and Neonatal Medicine, 1-4.
2Wolfe, et al (2011). The effect of maternal obesity on the rate of failed induction of labor. American Journal of Obstetrics and
Gynecology, 205(2), 128.e121-128.e127.
38. Obese poorer response to oxytocin
During Induction
• Walsh & Foley, 2010. Journal of Maternal-Fetal & Neonatal Medicine, 24(6), 817-
821.
– Prospective Irish standardized AML trial 1015 term, nulliparous induced women
– linear relationship BMI increase to cesarean despite oxytocin infusion per protocol
• Nuthalpaty et al, 2004. Obstetrics and Gynecology, 103(3), 452-456.
– Prospective IOL trial UAB 509 women, controlled for DM, etc.
– IUPC, pitocin infusion standardized, protocol
– Ran pitocin higher on obese women
• Lean women pit avg @ 16 mU/min
• Obese women pit avg @ 24 mU/min
– Obese women higher rate labor dystocia resulting in unplanned cesarean
For each additional 10kg of maternal weight, 17% increase in risk of
cesarean in this induction RCT
39. Obese poorer response oxytocin
augmentation
N= 2,143 term, nulliparous women spontaneous labor, Ireland
Prospective observational study, Active Management of Labor
protocol
Obese women significantly more likely to fail oxytocin
augmentation (require cesarean for dystocia despite
augment).
(Walsh & Foley, 2010)
40. Intrapartum
Interventions in the Labors of Obese
Women
How do
intrapartum
interventions
interact in the
unique
physiology of
an ?
obese
woman?
No Current Guidelines for Best Use of Intrapartum Interventions in
Obese Women
41. Timing of Interventions—Also
Important
Liberal guidelines for hospital admission
in early labor2
&
Often applied using stringent timelines
for labor progression3
2Jackson, 2003. Impact of Collaborative Management and Early Admission in Labor on
Method of Delivery. Journal of Obstetric, Gynecologic, and Neonatal Nursing, 32(2), 147-157.
3Lavender et al, 2012. Effect of partogram use on outcomes for women in spontaneous labour
at term. Cochrane Database Syst Rev, 8, CD005461.
46. Median Duration of Labor in Hours
(Slowest 5%ile) in Nulliparous
Women by BMI, normal neonates
(Kominiarek et al, 2011)
Cervical
dilation,
cm
BMI <25 BMI 25.0-
29.0
BMI 30-
34.9
BMI 35.0-
39.9
BMI ≥ 40 P value
for trend
4-10 cm 5.4 (18.2) 5.7 (18.8) 6.0 (19.9) 6.7 (22.2) 7.7 (25.6) < .0001
2nd stage
0.61 (2.5) 0.44 (1.9) 0.50 (2.1) 0.44 (1.9) 0.65 (2.7) .49
without
epidural
2nd stage
with
epidural
0.75 (2.6) 0.83 (2.8) 0.79 (2.7) 0.69 (2.4) 1.18 (3.7) .81
47. Median Duration of Labor in Hours
(Slowest 5%ile) in Multiparous
Women by BMI, normal neonates
(Kominiarek et al, 2011)
Cervical
dilation,
cm
BMI <25 BMI 25.0-
29.0
BMI 30-
34.9
BMI 35.0-
39.9
BMI ≥ 40 P value
for trend
4-10 cm 4.6 (17.5) 4.5 (17.4) 4.7 (17.9) 5.0 (19.0) 5.4 (20.6) < .0001
2nd stage
0.17 (1.0) 0.17 (1.0) 0.15 (0.9) 0.15 (0.9) 0.12 (0.7) <.0001
without
epidural
2nd stage
with
epidural
0.40 (1.7) 0.33 (1.5) 0.27 (1.2) 0.25 (1.1) 0.36 (1.6) <.0001
48. Slowest Cervical Dilation/Hour in
Active Phase Labor
Lowest range of normal=Need to intervene clinically
• Friedman (1954) 1cm/hr
• Zhang, 2002: 1cm/hr (mixed weight sample)
• Neal et al, 2010: 0.5 cm/hr (mixed weight sample)
• Kominiarek et al, 2011 (obese women):
– Slowest between 4-5cm: 0.15-0.11 cm/hr
(i.e. 6.3 to 9 hours/cm)
– Slowest between 5-6cm: 0.25-0.2 cm/hr
– Slowest in transition: 0.6 cm/hr
49. Take Away: Management of Obese
Pregnant Women
In Labor
If baby and mother stable, obese women average 0.5 cm/hr in
transition (1.6 cm/hr slowest)
May take up to 6 hours/cm in early active labor for BMI 30, up to 9 hours
for higher BMIs
Delay admission to L&D until active phase labor if possible
Allow TOL for EFW ≤ 5000g non-DM, ≤4500g DM
Running pitocin:
Obese women may need higher doses, run for longer periods of time
than normal-weight women
Avoid IOL whenever possible—obese women more likely to fail IOL
than normal weight women
Consider multi-day cervical ripening protocols
Consider multiple methods of cervical ripening
51. Postpartum in Obese Women
Immediate Postpartum
• Increased risk PPH (atonic)1
• VTE prophylaxis 1 wk class III?2
• Delayed lactogenesis3 (>60-72
hours)
• Reduced duration of lactation2
• PPD and anxiety4
Long-term Postpartum
• PPD & Anxiety
• Need to decrease weight (antenatal
lifestyle & dietary)5
• Testing for DM
• Follow-up for HTN
• Referrals—weight reduction
specialist, endocrine, etc. (ACOG #549)
1Blomberg, 2011. Maternal obesity and the risk of postpartum hemorrhage. Obstet Gynecol
118: 561-568.
2RCOG, 2012. Reducing the risk of thrombosis and embolism (#37).
3Lepe, M. et al (2011). Effect of maternal obesity on lactation: systematic review. Nutr Hosp,
26(6).
4Molyneaux et al, 2014. Obesity and mental disorders during pregnancy and postpartum: a
systematic review and meta-analysis. Obstet & Gynec 123(4), 857-867.
5van der Pligt, P., et al (2013). Systematic review of lifestyle interventions to limit postpartum weight
retention: implications for future opportunities to prevent maternal overweight and obesity following
childbirth. Obes Rev, 14(10), 792-805.
Review risks.
Remember that when we talk about OR, or increased risk, there are still many obese women who have relatively normal pregnancies, do not have to be induced, and enter labor with a plan for a vaginal delivery. This is still the norm, even in this population.
Molyneaux article: meta-analysis done 2014 of 62 studies on total of 540,373 women.
Increases in PTD found among obese women has been known for some time; When adjust these analyses for hypertension and diabetic disease in pregnancy, see these increases largely disappear.
Only recently 2013 do we have new information out of Sweden (nationwide cohort study, 1.5 million n) revealing increased, dose-dependent risk of extrememly PTD for obese women.
Nutritional Considerations for women who have had a bariatric procedure
Roux-en-Y gastric bypass
Protein, iron, vit B12, folate, vit D, calcium deficiencies
Supplement if deficient
Monitor CBC, iron, ferritin, calcium, vit D q trimester
Consider nutrition consultation
Denmark Cohort Study 2013
339 women with singleton delivery after bariatric surgery (84.4% gastric bypass)
matched to 1277 unexposed women
- Infants born after maternal bariatric surgery have lower birthweight, lower GA, 3.3x LOWER risk of LGA, 2-3x HIGHER risk of SGA than infants born by a matched group of women w/o bariatric surgery. The impact on SGA was even higher in the subgroup with gastric bypass.
Kjaer MM, Lauenborg J, Breum BM, et al. The risk of adverse pregnancy outcome after bariatric surgery: a nationwide register-based matched cohort study. Am J Obstet Gynecol 2013;208:464.e1-5.
Recommendations are independent of age, parity, smoking hx, race, and ethnic background.
Twin pregnancy – IOM recommends gest weight gain of 16.8-24.5kg (37-54 lbs) if normal weight, 14.1-22.7kg (31-50 lbs) if overweight, and 11.3-19.1kg (25-42 lbs) if obese.
Excess weight gain is associated with increased risk of hypertensive d/o’s, C-section, and LGA neonates
Graph from files of Johanna Warren, MD
Nutritional Considerations for women who have had a bariatric procedure
Roux-en-Y gastric bypass
Protein, iron, vit B12, folate, vit D, calcium deficiencies
Supplement if deficient
Monitor CBC, iron, ferritin, calcium, vit D q trimester
Consider nutrition consultation
Increased risk unplanned cesarean delivery.
Unplanned=not an elective c/s, not breech. These are women who went into labor, with the expectation that they would have a vaginal delivery.
Poobolan et al, 2008 meta-analysis found nullips had risk unplanned c/s double that of normal BMI women if obese, and triple if morbidly obese.
Results from the two meta-analyses were confirmed in this large study out of the CSL in 2011
N=
Found increased risk of unplanned c/s among obese.
Able to quntify that risk to
Kominiarek data used admission BMI
When compared to normal weight women having cesarean delivery, obese women have increased risk of serious complications.
As for the why of obese women so often ending up with c/s, studies indicate that this is primarily because obese women are more likely to be diagnosed with labor dystocia.
We will now review each of these three abnormalities which can cause labor dystocia, and talk about some of the research on obese women.
This brings us to the last mechanism for labor dystocia, the powers of labor.
This is the basis for the current theory explaining unplanned c/s in obese women.
Studies have shown that obese women have dysregulated powers of labor, or myometrial dysfunction.
Both in in vitro and in clinical studies we see this effect.
We will now discuss 4 examples of how an obese woman’s biology creates myometrial dysfunction. Many of these findings are very recently made, and have not been investigated fully in women. However, this biologic work is starting to reveal a picture of labor dystocia in obese women as a problem that probably involves multiple systems suffering from dysfunctions, creating an additive effect on labor.
Our first models of biologic difficulty in the labors of obese women:
Cholesterol. This graph looks a little bit like a contractile pattern we would see while monitoring a woman in labor.
Graph is showing a contraction pattern, but in this experiment, the contraction pattern we are seeing here is from a single bundle of myometrial cells.
Smooth muscle researchers are able to describe the contractions of myometrial cells by hooking them up to small electrodes, and suspending them in small containers of liquid.
This graph=myometrial cells exposed to increasing concnetrations of cholesterol
Increased cholesterol=contractions which are both further apart, and also have decreased force (the height of these peaks)
A second model helping to explain the myometrial dysfunction found among obese women in labor involves the hormone leptin.
Leptin has two known actions that may change labor in the obese woman.
First, similar to cholesterol, leptin decreases both the force and frequency of uterine contractions.
Diagram.
Top graph: control cell bundle
Second graph: another control cell bundle, this one exposed to addition of pitocin to the perfusate. You can see how the contractions get more forceful with pitocin.
Bottom graph: Cell bundle first exposed to leptin, then to pitocin. Unlike the second graph, you can see how the leptin-exposed cells do not respond to pitocin. Repeated exposure to pitocin has no effect, with contractions showing less force as time goes on.
Second, leptin has been shown to block cellular changes necessary for the ripening of both the uterine cervix and body of the uterus.
For cellular ripening to occur, the some cells in the cervix and upper uterus must undergo an organized cell death. Leptin appears to block this action, resulting in a slower ripening of the cervix and uterus in preparation for labor.
Leptin has multiple actions:
Keeps myometrial cells in proliferative phenotype, instead of moving to contractile phenotype as needed for labor (anti-apoptosis)
Decreases uterine contractions, spontaneous and in response to pit
Inhibits uterine remodeling of extracellular matrix, via matrix metalloproteinases (MMP) activation. Leptin prevented collagen degradation and MMP activation in human myo.
Researchers have also shown that there are problems with both oxytocin receptors and Connexin-43 connection in situations of obesity.
Oxytocin receptors=expressed on uterus in the hours preceding labor.
Allow uterus to respond to both natural and synthetic oxytocin.
Obesity=decreased expression these receptors
Implies that obese women would have a Decreased response to oxytocin.
Connexin-43 is the primary gap junction protein in the uterus. Allows the millions of myometrial cells in the uterus to perform as a unified whole, passing contractions down in an organized wave pattern to push the baby against the cervix.
Connections laid down in the 24 hours prior labor=expression of this protein in myometrial cells
Obesity=findings of decreased expression of Connexin-43 in uterus.
??Possible implications for the uterus having hard time initiating contractions, or working as a whole to pass contractions.
The synthetic oxytocin that is able to stimulate myometrial cells would further lower intracellular pH, thus perhaps be unable to enhance uterine contractions.
So now we’ve reviewed 4 biologic models of labor dystocia in obese women. Each of these biologic models would create hardships in a woman’s labor. However, the situation in an obese women is possibly particularly bad because she may be suffering from the effects of multiple dysfunctions happening at the same time.
I mentioned earlier that these biologic models of labor difficulty in the obese women are thought to perhaps work together to create problems.
To illustrate that point, these are pictures of a uterine model having contractions.
These electrophysiologic models of the uterus are created using a computer program, similar to models of cardiac function. These computer models are created to help us better understand how cellular changes in the muscle cells play out at the organ level.
Picutre c to the left: normal uterus with contraction passing in organized fashion as a wave from fundus to cervix.
Picture d to right: abnormal contraction pattern. Created when researchers inserted a small area of myocyte cells that were more resistant to contraction, such as we’ve seen in obese women from cholesterol and leptin.
Result in this model from this small area of myometrial difficulty: contraction wave starts, hits that abnormal area, and is disrupted, resulting in an unorganized firing of myometrial cells across the uterus.
Loose the wave pattern of normal contractions, the hallmark of normally progressing labors.
Used with cardiac modeling1
Bridge between cellular-level effects and tissue mechanics
Use to identify ‘arrhythmias’ and genetic/environmental causes & treatments
More recently expanded to uterine models2
1Clayton et al, 2011
2Aslanidi et al, 2011
Abenhaim study done on single site Montreal on 11,922 women. Intrapartum interventions controlled for: epidural, augmentation, IOL.
Confounders: age, parity, gestational age, prev c/s, DM, PIH, cervix on admit, IOL, BW.
Leeman study: CNM management, with emphasis on giving women time in labor.
LTM III survey (2013) n-2400 women U.S. found:
AROM to speed labor, 20%
Continuous electronic fetal monitoring 66%
Augmentation 31%
Medically-induced labor 30%
1/8 had no interventions,
Interventions tracked: Continuous fetal monitoring, AROM, IOL, augmentation
Also found that average cervical dilation of U.S. mothers when admitted to hospital was 3cm.
Various studies done on high-technology interventions have found them to be associated with increased risk c/s and longer labor.
So what does happen in the labors of obese women? In a systematic review of the literature Nancy and I completed last year, we found that all of these interventions performed more frequently on obese women…
We’ll now turn to look in more depth at the intrapartum interventions used in the labors of obese women.
As we reviewed earlier, these interventions have been found to explain much of the association between obesity and unplanned cesarean.
PROBLEM: we have no current guidelines to guide our use of intrapartum interventions in the labors of obese women.
We know that obese women are more likely to have interventions in their labors when compared to lean women.
We know that obese women are often needing more pitocin, run for longer periods of time, and are still ending up with labor dystocia.
We know that obese women are more often failing prostaglandins.
What we do not know is how, exactly, these medications and other interventions are interacting with the very different physiology present in the obese woman’s body.
We discussed earlier the many ways that an obese woman may be different than a lean woman in labor.
However, we have no protocols to guide our use of interventions given that very different physiology.
In the absence of these protocols, healthcare providers are left to take their best guess at proper dosages and timelines for medications and other interventions in labor.
Researchers of intrapartum interventions also have seen that the TIMING of interventions is important in the outcomes of labor.
Stringent progression guidelines and early admission to hospital in labor both found to often be present in decisions regarding timing of intervention.
IF timing is such an important part of how providers manage labors, Where do we get information that helps us decide WHEN to use interventions in a woman’s labor?
This is the Friedman labor curve, introduced 1950’s, MEDIAN RATES OF CERVICAL CHANGE FROM THIS STUDY USED AS MAJOR GUIDING FORCE IN INTRAPARTUM MANAGEMENT until recently.
N=500 nullips, 1.8% c/s rate, 96% sedated, 14% pitocin use, rectal exams every 1-2 hours. Obesity rate at that time among childbearing women (age 13-42 in this study)=9.7%
Active labor median 4.6 hours.. 95%ile 11.7 hours, 1.2 cm/hr
From this, introduced idea of graphically tracking women’s labors: partograph using median times.
Friedman’s graph of labor was pretty much the law for many decades.
Then, in the early 2000’s, several studies reported on labor progression graphs for contemporary populations that looked different than Friedman’s graph.
Here is a graph created from a large multisite retrospective observational study ,the CSL with information from women in spontaneous labor.
Can see that the nulliparous women, the PO line here, shows no maximal dilation slope. Instead, we see a gradual cervical change through labor, with some small speeding up at around 6-7cm.
Among multips, we do see an inflection line, but it is much later than described by Friedman. For this study, active phase labor seems to start around 6cm.
The trends toward longer labors in contemporary populations shown on the previous slide in small studies provoked the study which produced this graph: the CSL; multisite retrospective observational U.S. all normal maternal and neonatal outcomes 2002-2008
N=27,170 nullip, spontaneous labor, SVD
No consistent “active phase” pattern, or inflection point.
Median labor “should not be the basis of clinical diagnosis of protraction or arrest. Instead, use upper limit of normal labor to guide clinical interventions.
Here are the same techniques used to create labor progression curves for women by their BMI at delivery.
Can see that as women have higher BMI, their labor curves lengthen, straighten.
Also use CSL data, n= 44,326 nullips achieving vaginal birth, adjusted for age, DM, gestational age, augmentation, epid, BW, only women achieving 2nd state included here.
Here are the same data for multips women by BMI.
Similar to the nullips obese graph, see that increased BMI leads to longer course of labor, with more time in latent phase labor.
Unlike nullip lines, we do still see an inflection point happening for multips, at around 6-7 cm.
Also use CSL data, n= 44,326 nullips achieving vaginal birth, adjusted for age, DM, gestational age, augmentation, epid, BW, only women achieving 2nd state included here.
Here we can see the data that the previous graphs were based on.
Here, the median duration of labor is the first number you see, with the slowest 5th percentile for labor duration in parenthesis.
This slowest 5th percntile number is given because this is generally seen as the appropriate place where interventions to speed labor should occur—at the point where 95% of women would have already progressed past.
So, for lean women of normal BMI, median is 5.4, with 18.2 hours being the slowest we would normally see.
You can see that as the women’s BMI goes higher, her time in labor gets longer.
By contrast, when we look at the time it takes for women of different BMI to get through 2nd stage, obese women are actually faster than lean women.
These results from same multi-location clinic U.S. sample of 57,462 nulliparous women, mixture of induced, augmented, spontaneous labors.
Replicated in several other studies with populations from Europe and U.S. Canada.
BMI dose-dependent effect on progress
Here are the same data, but for multiparous women.
These results from same multi-location clinic U.S. sample of 61,516 multiparous women, mixture of induced, augmented, spontaneous labors.
Replicated in several other studies with populations from Europe and U.S. Canada.
BMI dose-dependent effect on progress
Clinicians often want a shorthand way of knowing if their patient is progressing normally through labor.
Problems with this shorthand way—
but
Based on Friedman’s 1950’s data, the lowest range of normal cervical dilation in active phase labor was used as the threshold after which the clinician should intervene clinically.
For years, clinicians were trained using Friedman’s recommendation that we should be seeing 1cm/hour after active phase labor for normal progression.
You can see here the updated estimates of active phase labor progress, as re-calculated using more modern populations of women.
Here is what we know about how best to care for obese women now in labor…
In other words, patience is a virtue with obese women. Midwifery, with attention to labor care that decreases rates of labor dystocia, can make a huge difference for all women, but especially for obese women.
As we work towards ways to prevent obesity from affecting so many childbearing women, we must move patiently through these women’s labors to achieve the best outcome possible.
Monitoring contractions: either toco or EHG equally sensitive.
Monitoring fetal heart rate is more reliable when using abdominal fetal electrocardiogram over ultrasound Doppler (like the Monica AN24, see http://www.monicahealthcare.com/products/).
Lepe article 2011 was a systematic review of prospective studies assessing effect of maternal obesity on lactation.
Vander Pligt 2013 study was a systematic review of effectiveness of lifestyle interventions in reducing postpartum weight. n-=11 studies, 10 were RCT. 6 trials helped women achieve weight loss, but methods best suited to help women not clear from this analysis. Diet and exercise seem to be important.
Molyneaux article: meta-analysis done 2014 of 62 studies on total of 540,373 women.