The Relationship Between Short Interpregnancy Intervals and Adverse Pregnancy Outcomes by Maternal Age in the United States, 2013-2015 Open Access

Haight, Sarah (2017)

Permanent URL: https://etd.library.emory.edu/concern/etds/t435gd973?locale=en
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Abstract

Objective: To examine the association between interpregnancy interval (IPI) and adverse pregnancy outcomes by maternal age (15-39) to U.S. mothers on their 2nd - 4th live birth.

Methods: Publically available birth certificate data and multivariable modified Poisson regression were utilized to assess risk of preterm birth (PTB), defined as <37 weeks' gestation, and severe maternal morbidity (having any of the following conditions: gestational hypertension, gestational diabetes, maternal transfusion, perineal laceration, ruptured uterus, and unplanned hysterectomy) by length of IPI (0-23 months from last live birth to conception of next pregnancy) for 1,460,135 U.S. singleton births from 2013-2015.

Results: Compared to 18-23 month IPIs, overall adjusted risk ratios (aRR) for PTB for 12-17, 6-11, and <6 month IPIs were 1.04 (95% Confidence Interval (CI): 1.02, 1.06), 1.17 (95% CI: 1.15, 1.19) and 1.55 (95% CI: 1.52, 1.58), respectively. Across single years of maternal age, PTB risk was elevated for IPIs <6 months (aRR range: 1.28-1.75). There was also elevated PTB risk for IPIs 6-11 months among ages 19-34 (aRR range: 1.10-1.27) but not among ages 35 and older. There was a protective association of maternal morbidity with 6-17 month IPIs among ages 20-37 (aRR range: 0.81-0.95) and with <6 month IPIs for ages 20-28 (aRR range: 0.88-0.93).

Conclusions: All mothers may be advised to avoid a <6 month IPI to protect the next child from PTB risk. However, for women older than 35, when compared to an IPI of 18-23 months, an IPI of 12-17 months may not increase PTB risk, but may reduce maternal morbidity risk.

Table of Contents

CHAPTER I. BACKGROUND.. 1

Preterm Birth and Interpregnancy Interval 1

Maternal Morbidity and Interpregnancy Interval 3

Sociodemographic Risk Factors. 4

Opposing Opinions. 5

Maternal Age. 6

CHAPTER II. EXTENDED METHODS. 8

Data Source and Study Population. 8

Interpregnancy Interval 8

Preterm Birth. 9

Maternal Morbidity. 9

Maternal Age. 11

Race/Ethnicity. 12

Education. 12

Marital Status. 13

WIC. 13

Pre-Pregnancy Smoking. 13

Pre-Pregnancy BMI 14

Parity. 14

Previous PTB, Pre-Pregnancy Hypertension, and Pre-Pregnancy Diabetes. 14

Plurality. 15

Study Restrictions. 15

Descriptive Analysis Methods. 16

Modeling Methods. 17

Software. 18

CHAPTER III. MANUSCRIPT.. 19

Introduction. 19

Materials and Methods. 20

Data Source and Study Population. 20

Interpregnancy Interval 21

Preterm Birth. 21

Maternal Morbidity. 22

Maternal Age. 23

Other Covariates. 24

Study Restrictions. 25

Descriptive Analysis Methods. 25

Modeling Methods. 26

Software. 27

Results. 27

Discussion. 29

CHAPTER IV. PUBLIC HEALTH IMPLICATIONS AND FUTURE DIRECTIONS. 33

Public Health Implications. 33

Future Directions. 34

CHAPTER V. TABLES AND FIGURES. 37

Table 1. Characteristics of the Study Population by Maternal Age at Beginning of Interpregnancy Intervala(N= 1,460,135). 37

Figure 1. Preterm Birth (PTB) and Interpregnancy Interval (IPI) by Maternal Age at Beginning of Interval, Adjusteda 38

Figure 2. Maternal Morbidity and Interpregnancy Interval (IPI) by Maternal Age at Beginning of Interval, Adjusteda 39

Table 3. Preterm Birth (PTB) and Interpregnancy Interval (IPI) by Maternal Age at Beginning of Interval, Unadjusted. 40

Table 4. Preterm Birth (PTB) and Interpregnancy Interval (IPI) by Maternal Age at Beginning of Interval, Adjusteda 41

Table 5. Maternal Morbidity and Interpregnancy Interval (IPI) by Maternal Age at Beginning of Interval, Unadjusted. 42

Table 6. Maternal Morbidity and Interpregnancy Interval (IPI) by Maternal Age at Beginning of Interval, Adjusteda 43

CHAPTER VI. REFERENCES. 44

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