impact of the “39-week rule” on adverse maternal outcomes ... · outcome n (%) n (%) aor (95%...
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Impact of the “39-Week Rule” on Adverse Maternal Outcomes: A Statewide Analysis
A. Caroline Cochrane, MD, MSc; Ryan Batson, MD; Meredith Aragon, MD, MPH; Molly Bedenbaugh, BS; Stella Self, PhD; Katheryn Isham, MD;
Kacey Eichelberger, MD
Term pregnancy
Viability
(23 weeks)
Late
term
(410 - 416)
Full
term
(390 - 406)
Early
term
(370 - 386)
Late
pre-term
(340 - 366)
Post
term
(420 →)
Increase risk of
stillbirth Increase risk of:
- Pulmonary hypoplasia/RDS
- Necrotizing enterocolitis
- Infection
- Death
Evidence of increased adverse neonatal outcomes with early term delivery
ACOG & SMFM adopt the “39-week rule”
Medicaid and Blue Cross Blue Shield establish a non-payment policy for elective inductions prior to 39 weeks
Downstream effects
• Some scarce neonatal data available
• Unknown effects on maternal outcomes as a result of increasing gestational age
Objective
• Quantify the differences in adverse maternal outcomes as a result of widespread implementation of the “39-week rule” in South Carolina
Hypothesis
• There has been a shift in adverse maternal outcomes as an unintended consequence of the “39-week rule”
Methods
• Retrospective cohort study
• Term, singleton births in the state of South Carolina
• Group 1: “Pre-implementation” 1/1/2000 – 12/31/2008
• Group 2: “Post-implementation” 1/1/2013 – 12/31/2017
• Obtained all ICD codes, maternal age, race, BMI, and gestational age at time of delivery
• 1 week prior to delivery to 90 days post delivery
• Births having one or more codes for any outcome were counted as having an incidence of that outcome
Composite
Adverse Maternal
Outcomes
Cesarean
DeliveryHypertensive
Disorder
Postpartum
Hemorrhage
Placental
Abruption
Intrahepatic
Cholestasis
ICU
Admission
Blood
Transfusion
High Degree
Laceration
Maternal
Infection
Statistics
• Propensity score analysis was used to control for maternal age, race, and BMI to eliminate confounding data
• Outcome incidences were compared using the Cochran-Mantel-Haenszel(CMH) test, with any p-value <0.05 considered to be significant.
• Adjusted common odds ratio was used to determine direction of the significant differences
• All analysis performed in R version 3.5.2.
Study Population
Group 1
(Delivery between 2000-2008)
n = 412,632
Group 2
(Delivery between 2013-2017)
n = 221,353
P value
Maternal age (years)
< 20 57,846 (14.02%) 16,895 (7.63%) <0.01
20-29 234,447 (56.82%) 125,528 (56.71%) <0.01
30-39 113,681 (27.55%) 74,612 (33.71%) <0.01
> 39 6,658 (1.61%) 4,318 (1.95%) <0.01
Maternal race
Black/African American 136,088 (32.98%) 69,069 (31.20%) <0.01
White/Caucasian 267,133 (64.74%) 146,407 (66.14%) <0.01
Indian 6,045 (1.46%) 5,772 (2.61%) <0.01
Other 3,366 (0.82%) 105 (0.05%) <0.01
Maternal BMI
< 18.5 10,208 (2.47%) 8,383 (3.79%) <0.01
18.5 – 24.9 106,063 (25.7%) 90,210 (40.75%) <0.01
25 – 29.9 224,016 (54.29%) 57,600 (26.02%) <0.01
30 – 34.9 41,617 (10.09%) 33,135 (14.97%) <0.01
35 – 39.9 17,513 (4.24%) 17,616 (7.96%) <0.01
> 39 13,215 (3.2%) 14,409 (6.51%) <0.01
Payor status
Medicaid 118, 528 (28.72%) 115,036 (51.97%) <0.01
Private insurance 91,721 (22.23%) 88,607 (40.03%) <0.01
Self pay 15,993 (3.88%) 6,742 (3.05%) <0.01
Other 13,164 (3.19%) 10,148 (4.58%) <0.01
Unknown 173,226 (41.98%) 820 (0.37%) <0.01
Patient
Demographics
Patient Demographics
Group 1
n = 412,632
N (%)
Group 2
n = 221,353
N (%)
P value
Gestational age at time of
delivery
37w0d-38w6d 139,557 (33.82%) 63,444 (28.66%) <0.01
39w0d-≥ 41w 273,075 (66.18%) 157,909 (71.34%) <0.01
↓ 5.16%
Outcomes of Interest
Group 1
(n=412,632)
Group 2
(n=221,353)
Outcome N (%) N (%) AOR (95% CI) P value
Composite value 164,803 (39.94%) 94,658 (42.76%) 1.0580 (1.0468, 1.0633) <0.01 ↑2.82%
*Controlled for maternal age, race, and BMI
Outcomes of Interest
Group 1
(n=412,632)
Group 2
(n=221,353)
Outcome N (%) N (%) AOR (95% CI) P value
Cesarean delivery 122,116 (29.59%) 70,428 (31.82%) 1.0264 (1.0148, 1.0382) < 0.01
Hypertensive disorder diagnosis 31,960 (7.75%) 22,350 (10.10%) 1.3138 (1.2903, 1.3378) <0.01
Chorioamnionitis 5,982 (1.45%) 4,257 (1.92%) 1.4402 (1.3837, 1.4991) <0.01
Intrahepatic cholestasis 264 (0.06%) 798 (3.63%) 5.2959 (4.6044, 6.0911) <0.01
Blood transfusion 2,815 (0.68%) 2,308 (1.04%) 1.5696 (1.4845, 1.6595) <0.01
ICU admission 4,643 (1.13%) 6,734 (3.04%) 2.5959 (2.4988, 2.6969) <0.01
↑ 2.23%
↑ 2.35%
↑ 0.47%
↑ 3.57%
↑ 0.36%
↑ 1.91%
*Controlled for maternal age, race, and BMI
Outcomes of Interest
Group 1
(n=412,632)
Group 2
(n=221,353)
Outcome N (%) N (%) AOR (95% CI) P value
High degree lacerations* 13,456 (4.63%) 3,898 (2.58%) 0.5405 (0.5211, 0.5605) <0.01 ↓ 2.05%
*Controlled for maternal age, race, and BMI
Outcomes of Interest
Group 1
(n=412,632)
Group 2
(n=221,353)
Outcome N (%) N (%) AOR (95% CI) P value
Postpartum
hemorrhage 11,659 (2.83%) 6,173 (2.79%) 0.9988 (0.9678, 1.0308) 0.9472
Placental abruption 3,016 (0.73%) 1,700 (0.77%) 1.0092 (0.9505, 1.718) 0.7744
*Controlled for maternal age, race, and BMI
Hypertensive DisordersGroup 1
(n=412,632)
Group 2
(n=221,353)
Outcome N (%) N (%) AOR (95% CI) P value
Gestational hypertension
16,425
(3.98%)
12,439
(5.62%)
1.4049
(1.3715, 1.4392) <0.01
Preeclampsia without severe features
10,264
(2.49%)
6,087
(2.75%)
1.1242
(1.0884, 1.1613) <0.01
Preeclampsia with severe features /
HELLP
2,032
(0.49%)
2,046
(0.92%)
1.9231
(1.8070, 2.0468) <0.01
Eclampsia
397
(0.10%)
235
(0.11%)
1.2111
(1.0286, 1.4259) 0.0242
Chronic hypertension with
superimposed preeclampsia
1,216
(0.29%)
1,378
(0.62%)
1.8484
(1.7097, 1.9983) <0.01
Unspecified hypertension in pregnancy
2,871
(0.70%)
1,856
(0.84%)
1.1260
(1.0613, 1.1947) <0.01
↑ 1.64%
↑ 0.26%
↑ 0.43%
↑ 0.01%
↑ 0.33%
↑ 0.06%
*Controlled for maternal age, race, and BMI
Discussion
• Overall number of deliveries in the early term period decreasedsignificantly
• Diagnosis of all hypertensive disorders significantly increased
• Incidence of C-section increased
• Incidence of blood transfusion, ICU admission, maternal infection, IHC increased
• Incidence of high degree lacerations decreased
Strengths
• Large sample size
• Generalizable results
• Changing maternal demographics were controlled
Limitations
• Analysis limited to coding data
• Patient ethnicity information unavailable
• Cannot control for other shifts in population health or physician practice
Conclusions
• Incidence of several adverse maternal outcomes have increased since implementation of the 39-week rule
• This difference persists after controlling for changes in maternal race, age, and BMI
• Cannot control for changes in overall population health
• As the only country in the world with an increasing maternal mortality rate, a much closer look at the 39-week rule is warranted
Questions?
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