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The impact of postpartum contraception on reducing preterm birth: findings from California

      Objective

      Family planning is recommended as a strategy to prevent adverse birth outcomes. The potential contribution of postpartum contraceptive coverage to reducing rates of preterm birth is unknown. In this study, we examine the impact of contraceptive coverage and use within 18 months of a birth on preventing preterm birth in a Californian cohort.

      Study Design

      We identified records for second or higher-order births among women from California’s 2011 Birth Statistical Master File and their prior births from earlier Birth Statistical Master Files. To identify women who received contraceptive services from publicly funded programs, we applied a probabilistic linking methodology to match birth files with enrollment records for women with Medi-Cal or Family Planning, Access, Care, and Treatment Program (PACT) claims. The length of contraceptive coverage was determined through applying an algorithm based on the specified method and the quantity dispensed. Preterm birth was defined as a birth occurring <37 weeks’ gestation, and calculated from the medical record. We further examined differences in preterm birth using subcategories defined by the World Health Organization: extremely preterm (<28 weeks); very preterm (28 to <32 weeks); and moderate to late preterm (32 to <37 weeks). We built a multivariable regression model to examine the effect of contraceptive coverage on the odds of a preterm birth and control for key covariates.

      Results

      The cohort consisted of 111,948 women who were seen at least once by a Medi-Cal or Family PACT provider within 18 months of delivery. Of the cohort, 9.75% had a preterm birth. Contraceptive coverage was found to be protective against preterm birth. For every month of contraceptive coverage, odds of a preterm birth <37 weeks decrease by 1.1% (odds ratio, 0.989; 95% confidence interval, 0.986–0.993).

      Conclusion

      Improving postpartum contraceptive use has the potential to reduce preterm births.

      Key words

      See related editorial, page 602
      Preterm birth (<37 weeks’ gestational age) remains a significant cause of neonatal morbidity and mortality in the United States and globally.
      • Zhu B.P.
      • Le T.
      Effect of interpregnancy interval on infant low birth weight: a retrospective cohort study using the Michigan maternally linked birth database.
      • Ananth C.V.
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      • et al.
      Global, regional, and national causes of child mortality: an updated systematic analysis for 2010 with time trends since 2000.
      Preterm birth is now the second most common cause of death in children age <5 years, with an estimated 1.1 million infants dying annually from complications of preterm birth.
      • Liu L.
      • Johnson H.L.
      • Cousens S.
      • et al.
      Global, regional, and national causes of child mortality: an updated systematic analysis for 2010 with time trends since 2000.
      It is also an important factor in long-term morbidity, such as cognitive, visual, and learning impairments.
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      Lancet Neonatal Survival Steering Team. 4 Million neonatal deaths: When? Where? Why?.
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      Long-term neurodevelopmental outcomes after intrauterine and neonatal insults: a systematic review.
      Reduction in mortality from preterm birth, and prevention of preterm birth, is the focus of national and international efforts.
      March of Dimes, Save the Children, WHO
      Born too soon: the global action report on preterm birth.
      However, although prevention of preterm birth is a public health priority, international estimates reveal it to be a persistent and substantial problem in a wide range of countries.
      • Blencowe H.
      • Cousens S.
      • Oestergaard M.Z.
      • et al.
      National, regional, and worldwide estimates of preterm birth rates in the year 2010 with time trends since 1990 for selected countries: a systematic analysis and implications.
      In the United States, the rate of preterm birth increased by nearly 30% from 1981 through 2006.
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      • Hamilton B.E.
      • Ventura S.J.
      • Osterman M.J.
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      Births: final data for 2010.
      In 2007, this trend began to reverse, with a decline from a high of 12.8% in 2006 to 11.73 in 2011.
      • Martin J.A.
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      Births: final data for 2010.
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      Centers for Disease Control and Prevention. Preterm births–United States, 2006 and 2010.
      • Martin J.A.
      • Hamilton B.E.
      • Ventura S.J.
      • Osterman M.J.
      • Mathews T.J.
      Births: final data for 2011.
      Despite this promising trend in preterm birth rates, the overall number of premature infants born in the United States remains higher than in any single year from 1981 through 2006, and significant racial and ethnic disparities exist.
      • Martin J.A.
      • Hamilton B.E.
      • Ventura S.J.
      • Osterman M.J.
      • Wilson E.C.
      • Mathews T.J.
      Births: final data for 2010.
      • Martin J.A.
      • Osterman M.J.
      Centers for Disease Control and Prevention. Preterm births–United States, 2006 and 2010.
      The causes of preterm birth are multifactorial and poorly understood, making prevention challenging.
      • Chang H.H.
      • Larson J.
      • Blencowe H.
      • et al.
      Preventing preterm births: analysis of trends and potential reductions with interventions in 39 countries with very high human development index.
      A range of different interventions such as progesterone supplementation, cerclage, smoking cessation, reduction in transfer of multiple embryos with assisted reproductive technology, and eliminating nonmedically indicated inductions have been evaluated for their potential to reduce preterm birth.
      • Chang H.H.
      • Larson J.
      • Blencowe H.
      • et al.
      Preventing preterm births: analysis of trends and potential reductions with interventions in 39 countries with very high human development index.
      Even with full implementation of these complex interventions however, the estimated reduction in rates of preterm birth would be small.
      • Chang H.H.
      • Larson J.
      • Blencowe H.
      • et al.
      Preventing preterm births: analysis of trends and potential reductions with interventions in 39 countries with very high human development index.
      To effectively and equitably reduce preterm birth rates, there is an urgent need to address the underlying social determinants of poor reproductive health.
      • Iams J.D.
      American Gynecological and Obstetrical Society 2013: social determinants of reproductive health.

      Iams JD. Presidential address. American Gynecological and Obstetrical Society 32nd annual meeting; 2014. Available at: . http://www.agosonline.org/public/PDF/2013/11-iams.pdf. Accessed December 13, 2014.

      • Kim D.
      • Saada A.
      The social determinants of infant mortality and birth outcomes in Western developed nations: a cross-country systematic review.
      Individual socioeconomic status, inequalities in income and education, social policies, neighborhood deprivation, and intermediary factors such as health behaviors are examples of social determinants of health.

      Iams JD. Presidential address. American Gynecological and Obstetrical Society 32nd annual meeting; 2014. Available at: . http://www.agosonline.org/public/PDF/2013/11-iams.pdf. Accessed December 13, 2014.

      • Kim D.
      • Saada A.
      The social determinants of infant mortality and birth outcomes in Western developed nations: a cross-country systematic review.
      Influencing health behaviors through preconception care is one strategy that has been adopted to try and improve reproductive outcomes. Attention has focused on the potential for preconception and interconception care to reduce preterm birth by promoting birth spacing and preventing unintended pregnancy, in particular among adolescents.
      March of Dimes, Save the Children, WHO
      Born too soon: the global action report on preterm birth.
      • Salihu H.M.
      • August E.M.
      • Mbah A.K.
      • et al.
      The impact of birth spacing on subsequent feto-infant outcomes among community enrollees of a federal healthy start project.
      • Teitler J.O.
      • Das D.
      • Kruse L.
      • Reichman N.E.
      Prenatal care and subsequent birth intervals.
      Optimizing interpregnancy interval through birth spacing is one proposed solution for reducing adverse birth outcomes.
      • Zhu B.P.
      • Le T.
      Effect of interpregnancy interval on infant low birth weight: a retrospective cohort study using the Michigan maternally linked birth database.
      • Conde-Agudelo A.
      • Rosas-Bermudez A.
      • Kafury-Goeta A.C.
      Effects of birth spacing on maternal health: a systematic review.
      Evidence suggests that risks of preterm birth, low birthweight, and small-for-gestational-age infants are minimized when interpregnancy intervals are between 18–23 months.
      • Zhu B.P.
      • Le T.
      Effect of interpregnancy interval on infant low birth weight: a retrospective cohort study using the Michigan maternally linked birth database.
      • Conde-Agudelo A.
      • Rosas-Bermudez A.
      • Kafury-Goeta A.C.
      Effects of birth spacing on maternal health: a systematic review.
      • Zhu B.P.
      • Rolfs R.T.
      • Nangle B.E.
      • Horan J.M.
      Effect of the interval between pregnancies on perinatal outcomes.
      • Zhu B.P.
      • Haines K.M.
      • Le T.
      • McGrath-Miller K.
      • Boulton M.L.
      Effect of the interval between pregnancies on perinatal outcomes among white and black women.
      However, optimizing interpregnancy intervals alone is not enough to reduce adverse birth outcomes; it has also been proposed that interpregnancy intervals are a proxy for maternal variables that cannot be easily monitored, such as attitudes, lifestyle, and cultural norms.
      • Ball S.J.
      • Pereira G.
      • Jacoby P.
      • de Klerk N.
      • Stanley F.J.
      Re-evaluation of link between interpregnancy interval and adverse birth outcomes: retrospective cohort study matching two intervals per mother.
      Analyses that compare interpregnancy intervals and birth outcomes from the same woman control for these factors, and can clarify the association between adverse birth outcomes and different variables.
      • Ball S.J.
      • Pereira G.
      • Jacoby P.
      • de Klerk N.
      • Stanley F.J.
      Re-evaluation of link between interpregnancy interval and adverse birth outcomes: retrospective cohort study matching two intervals per mother.
      Data from California provide an opportunity to examine the relationship between postpartum contraception and birth outcomes in detail. In 2011, the costs of half of all births in California (50.4%) were paid for by Medicaid (Medi-Cal).

      Research and Analytic Studies Division, California Department of Health Care Services. Medi-Cal statistical brief. Sacramento, CA, 2014. Available at: http://www.dhcs.ca.gov/dataandstats/statistics/Documents/RASD_Issue_Brief_MC_Births.pdf. Accessed Dec. 13, 2014.

      Women who have their delivery paid by Medi-Cal continue to be eligible for postpartum and pregnancy-related services, through the end of the second month after the month of delivery, and may then be eligible to receive family planning services through Medi-Cal, or California’s family planning program, Family Planning, Access, Care, and Treatment Program (PACT).

      Medi-Cal Services for Immigrants, Including Non-Citizens and Undocumented Immigrants. http://www.healthconsumer.org/Medi-CalOverview2008Ch14.pdf. Accessed December 13, 2014.

      • Thiel de Bocanegra H.
      • Chang R.
      • Menz M.
      • Howell M.
      • Darney P.
      Postpartum contraception in publicly funded programs and interpregnancy intervals.
      Previous research from California has established the importance of publicly funded family planning programs in establishing optimal interpregnancy intervals through ensuring access to postpartum contraception and promoting use of highly effective methods of contraception.
      • Thiel de Bocanegra H.
      • Chang R.
      • Menz M.
      • Howell M.
      • Darney P.
      Postpartum contraception in publicly funded programs and interpregnancy intervals.
      • Thiel de Bocanegra H.
      • Chang R.
      • Howell M.
      • Darney P.
      Interpregnancy intervals: impact of postpartum contraceptive effectiveness and coverage.
      Women with a postpartum visit were 33% less likely to have a short interpregnancy interval than women who did not (relative risk 0.67).
      • Thiel de Bocanegra H.
      • Chang R.
      • Menz M.
      • Howell M.
      • Darney P.
      Postpartum contraception in publicly funded programs and interpregnancy intervals.
      The protective effect varies by contraceptive method dispensed. Women receiving the most effective forms of contraception (long-acting, reversible methods, eg, the intrauterine device and implant) had significantly increased odds of achieving an optimal birth interval.
      • Thiel de Bocanegra H.
      • Chang R.
      • Howell M.
      • Darney P.
      Interpregnancy intervals: impact of postpartum contraceptive effectiveness and coverage.
      Because of the uncertainty of a causal mechanism between interpregnancy intervals and preterm birth, we wanted to directly examine the potential impact of provision of postpartum contraception in reducing preterm birth.
      • Ball S.J.
      • Pereira G.
      • Jacoby P.
      • de Klerk N.
      • Stanley F.J.
      Re-evaluation of link between interpregnancy interval and adverse birth outcomes: retrospective cohort study matching two intervals per mother.
      Family planning is recommended as a strategy to prevent adverse birth outcomes.
      • Martin J.A.
      • Osterman M.J.
      Centers for Disease Control and Prevention. Preterm births–United States, 2006 and 2010.
      The potential contribution of postpartum contraceptive coverage to reducing rates of preterm birth is unknown. We hypothesized that postpartum contraception would be associated with a significant reduction in preterm birth. In this study, we examine the impact of contraceptive coverage and use within 18 months of a birth on preventing preterm birth in a Californian cohort.

      Materials and Methods

      The data analysis was approved by the University of California, San Francisco, Committee of Human Subjects Approval and the California State Committee of Human Subjects Protection. We built a cohort of women aged 12–44 years who received publicly funded contraceptive services in the 18 months after birth. We identified records for second or higher-order births among women from California’s 2011 Birth Statistical Master File and their prior births from earlier Birth Statistical Master Files. Outcomes are reported for the 2011 birth. The birth immediately prior to the 2011 birth is referred to as the “index birth.” Women whose index births occurred before Jan. 1, 2005, or outside California were excluded. Other exclusions were: multiple births, unknown last menstrual period, missing birth date data, documented sterilization at time of index birth, birth intervals of <30 days, and missing or improbable maternal age (eg, age <12 years at the time of the birth).
      To identify women who received contraceptive services from publicly funded programs, we applied a probabilistic linking methodology to match Birth Statistical Master Files maternal data with enrollment records for women with Medi-Cal or Family PACT claims. The linking algorithm determines whether a pair of records from 2 disparate data files belongs to the same person.
      • Thiel de Bocanegra H.
      • Chang R.
      • Menz M.
      • Howell M.
      • Darney P.
      Postpartum contraception in publicly funded programs and interpregnancy intervals.
      • Thiel de Bocanegra H.
      • Chang R.
      • Howell M.
      • Darney P.
      Interpregnancy intervals: impact of postpartum contraceptive effectiveness and coverage.
      • Winkler W.
      Frequency based matching in Fellegi-Sunter model of record linkage.
      We used the state’s Management Information System/Decision Support System to analyze administrative Medi-Cal and Family PACT clinic and pharmacy claims, and encounter data, to identify the provision of contraceptive methods. Women were defined as receiving contraception if they had at least 1 Medi-Cal or Family PACT claim for receipt of a contraceptive method. Emergency contraception was excluded from the definition of method of contraception received.

      Variables

      This study explores whether contraceptive coverage and use within 18 months of the index birth were associated with decreased odds of a preterm birth. Contraceptive coverage estimates the amount of contraceptive supply that a woman received. The length of coverage is determined through applying an algorithm based on the specified method and the quantity dispensed (eg, the number of pill packs or condoms distributed) from pharmacy and on-site claims during the study period. For cases of method switching, coverage was calculated on the aggregate of both methods without double counting periods of overlap. In cases of multiple contraceptive method provision, coverage was estimated based on the most effective method. The cutoff and maximum length of coverage was set at 18 months from a woman’s index birth. For long-acting reversible contraceptives (LARC) such as the intrauterine device and implant, unless a removal claim was found, we assigned the maximum length of coverage. The length of coverage was summed across service dates from the first postpartum visit until the 18-month cutoff.
      Preterm birth was defined as a birth occurring <37 weeks’ gestation, and calculated from the medical record. Preterm birth was further examined using subcategories defined by the World Health Organization: extremely preterm (<28 weeks); very preterm (28 to <32 weeks); and moderate to late preterm (32 to <37 weeks).
      • Blencowe H.
      • Cousens S.
      • Oestergaard M.Z.
      • et al.
      National, regional, and worldwide estimates of preterm birth rates in the year 2010 with time trends since 1990 for selected countries: a systematic analysis and implications.
      Births with ≥37 weeks’ gestational length were defined as term births.
      Client demographics for the mother were determined from the information recorded in the 2011 Birth Statistical Master File. Demographic variables consisted of education level (less than high school graduate, high school graduate/some college, or college graduate or more), race/ethnicity (white, black, Hispanic, Asian/Pacific Islander, Native American, or other/unknown), nativity (United States or foreign-born), age at index birth (continuous variable), and parity (2 births or >2 births). Univariate analyses were conducted on the demographic variables to examine the distribution of the cohort.

      Multivariable Model

      We constructed a multivariate logistic model examining the relationship of contraceptive coverage with the outcome of preterm birth. Contraceptive coverage was defined as a continuous variable from 0–18 months. We controlled for demographic variables, including education level, race/ethnicity, nativity, age at index birth, and parity. We used software (SAS, version 9.2, PROC LOGISTIC; SAS Institute, Cary, NC) for all analyses.

      Results

      Sample characteristics

      The cohort consisted of 111,948 women who were seen at least once by a Medi-Cal or Family PACT provider within 18 months of delivery (Table 1). Of these women, 9.8% had a preterm birth. Among women with a preterm birth, 86.9% were moderate to late preterm, 8.6% very preterm, and 4.5% extremely preterm births. In the study cohort, nearly 95% of the births were normal-weight infants.
      Table 1Sample characteristics
      Characteristicn

      111,948
      Total

      percentage
      Preterm birth
       Term101,03490.25
       Moderate to late preterm (32–37 wk)94838.47
       Very preterm (28–32 wk)9390.84
       Extremely preterm (<28 wk)4920.44
      Birthweight
       Normal (>2500 g)106,13694.81
       Low (<2500 g)49134.39
       Very low (<1500 g)4780.43
       Extremely low (<1000 g)4210.38
      Patient characteristics
      Age at index birth, y
       <2023,93021.38
       20–2971,28963.68
       30–3916,40014.65
       >403290.29
      Race/ethnicity
       White16,19814.47
       Hispanic79,08770.65
       black84327.53
       Asian/Pacific Islander58855.26
       Native American6870.61
       Other/unknown16591.48
      Education
      <12th grade42,41137.88
      High school graduate/some college62,35255.7
      Bachelor degree or greater42093.76
       Data missing29762.66
      Country of birth
       United States61,29454.75
       Foreign born50,65445.25
      Parity
       2 births51,92346.38
       >2 births60,01653.61
       Data missing90.01
      Rodriguez. Postpartum contraception reduces preterm birth. Am J Obstet Gynecol 2015.
      Most of the women received user-dependent hormonal contraceptives as their most effective method (Table 2) (54,845; 49.0%). A much smaller percentage used barrier methods (9141; 8.2%), followed by LARCs (9048, 8.1%). Approximately one-third of the women (38,914; 34.8%) had no contraceptive claims. In the entire cohort, including women with no contraceptive use, the average length of coverage was 5.1 months. Among contraceptive users, the average length of coverage was 7.7 months.
      Table 2Categories and distribution of contraceptive methods
      Maximum tierContraceptive methods includedn%Mean coverage, mo
      1IUD; implant90488.111.5
      2Oral contraceptive pill (combined and progestin only); progestin injectable; hormonal patch; hormonal ring54,84549.07.8
      3Male and female condoms; cervical cap91418.20.6
      No methodNone; withdrawal; natural family planning38,91434.8
      Total111,948100
      IUD, intrauterine device.
      Rodriguez. Postpartum contraception reduces preterm birth. Am J Obstet Gynecol 2015.
      Most of the population was Hispanic (70.7%), followed by non-Hispanic white (14.5%). The remaining groups were smaller, and ranged from 7.5% black, 5.3% Asian/Pacific Islander, to <1% Native American, and 1.5% other/unknown. Approximately 45% of the cohort was born outside of the United States. Of women, 38% had less than a high school diploma, and 56% had a high school degree or some college. Only 4% in the sample were college graduates. Nearly two-thirds of the women (64%) were 20–29 years old at the time of the index birth. Of the women, 21% were <20 years old, and 15% of them were >30 years old.

      Regression analysis

      The logistic regression model estimated the odds of preterm birth by contraceptive coverage while controlling for variables that may also impact risk of preterm birth, such as age at index birth, parity, race/ethnicity, education level, and country of birth. Our study shows that contraceptive coverage is protective against preterm birth (Table 3). For every month of contraceptive coverage, odds of a preterm birth <37 weeks’ decrease by 1.1% (Table 3) (odds ratio [OR], 0.989; 95% confidence interval [CI], 0.986–0.993). Increased education level was associated with decreased odds of preterm birth (Table 3) (OR, 0.689; 95% CI, 0.610–0.779). Increased odds of preterm birth were noted with all non-white race/ethnicities. Black women had the highest risk of preterm birth (Table 3) (OR, 1.623; 95% CI, 1.495–1.762) and Asian/Pacific Islanders the lowest increased risk (OR, 1.217; 95% CI, 1.095–1.352) compared with white women. No significant difference in risk of preterm birth was noted by country of birth, age at index birth, or parity.
      Table 3Association of contraceptive coverage with preterm birth
      <37 wk
      Odds ratio95% CI
      Contraceptive coverage per month (reference no coverage)0.9890.986–0.993
      Race (reference group white)
       Hispanic1.0981.031–1.17
       black1.6231.495–1.762
       Asian/Pacific Islander1.2171.095–1.352
       Native American1.2871.015–1.632
       Other/unknown1.0020.741–1.356
      Education (reference group <12th grade)
       High school graduate/some college0.9170.876–0.959
       Bachelor degree or greater0.6890.61–0.779
      Country of birth (reference group born in United States)
       Foreign born0.80.762–0.84
      Age at index birth1.021.015–1.025
      Parity1.1991.146–1.255
      CI, confidence interval.
      Rodriguez. Postpartum contraception reduces preterm birth. Am J Obstet Gynecol 2015.

      Comment

      Our findings demonstrate a small, but significant reduction in preterm births attributable to provision of postpartum contraception in a diverse cohort of Medicaid patients. We found that for every month of contraceptive coverage, odds of a preterm birth decrease by 1.1%. This finding compares favorably with estimates of preterm birth reduction due to other interventions.
      • Chang H.H.
      • Larson J.
      • Blencowe H.
      • et al.
      Preventing preterm births: analysis of trends and potential reductions with interventions in 39 countries with very high human development index.
      For example, broadly implementing smoking cessation and progesterone supplementation interventions would have an estimated 0.01–0.3% reduction in rate of preterm births.
      • Chang H.H.
      • Larson J.
      • Blencowe H.
      • et al.
      Preventing preterm births: analysis of trends and potential reductions with interventions in 39 countries with very high human development index.
      • Petrini J.R.
      • Callaghan W.M.
      • Klebanoff M.
      • et al.
      Estimated effect of 17 alpha-hydroxyprogesterone caproate on preterm birth in the United States.
      Scaling up cerclage services would result in an estimated 0.15% rate reduction and decreasing transfer of multiple embryos with assisted reproductive technology would yield an estimated 0.06% rate reduction in preterm births.
      • Chang H.H.
      • Larson J.
      • Blencowe H.
      • et al.
      Preventing preterm births: analysis of trends and potential reductions with interventions in 39 countries with very high human development index.
      With 6 months of additional contraceptive coverage, preterm birth would decline by 6.3%.
      A 50% reduction goal for preterm birth-specific mortality by 2025 has been set in the “Born Too Soon” report, and a wide range of interventions are being implemented to both prevent preterm birth and improve survival for preterm infants.
      March of Dimes, Save the Children, WHO
      Born too soon: the global action report on preterm birth.
      Scaling up access to postpartum contraception, in particular the most effective forms (LARC), is a core strategy for meeting international development goals pertaining to maternal and child health, including preterm birth prevention.
      WHO
      Ensuring human rights in the provision of contraceptive information and services.
      WHO
      Accelerating progress towards the attainment of international reproductive health goals: a framework for implementing the WHO global reproductive health strategy.
      In our population, LARC methods accounted for 8.1% of users and provided a mean of 11.7 months of contraceptive coverage. Assisting women using less effective methods of contraception (eg, barrier or withdrawal) or no method to transition to LARC has the potential to further reduce preterm birth rates.
      Implementing contraceptive counseling antenatally or immediate postpartum provision of contraception are 2 additional strategies to improve effective postpartum use.
      WHO
      Ensuring human rights in the provision of contraceptive information and services.
      WHO
      Family planning: a global handbook for providers.
      Timing of contraceptive initiation varies in the postpartum period.
      Centers for Disease Control and Prevention
      Contraceptive use among postpartum women–12 states and New York City, 2004-2006.
      The routine postpartum visit usually occurs around 6 weeks’ postpartum.
      • Speroff L.
      • Mishell Jr., D.R.
      The postpartum visit: it's time for a change in order to optimally initiate contraception.
      However, this places a large proportion of women at risk for pregnancy. Studies have reported that >50% of nonbreast-feeding women have had intercourse prior to their scheduled 6-week postpartum visit, and some of these women will have already ovulated.
      • Glazener C.M.
      Sexual function after childbirth: women's experiences, persistent morbidity and lack of professional recognition.
      • Elliott S.A.
      • Watson J.P.
      Sex during pregnancy and the first postnatal year.
      • Connolly A.
      • Thorp J.
      • Pahel L.
      Effects of pregnancy and childbirth on postpartum sexual function: a longitudinal prospective study.
      • Woranitat W.
      • Taneepanichskul S.
      Sexual function during the postpartum period.
      Many providers delay contraceptive counseling for a variety of reasons that are not evidence based until after the resumption of ovulation and intercourse has occurred.
      • Speroff L.
      • Mishell Jr., D.R.
      The postpartum visit: it's time for a change in order to optimally initiate contraception.
      Efforts to improve early contraceptive counseling and provision during obstetric care is a critical strategy to prevent unintended pregnancy and prevent adverse birth outcomes.
      WHO
      Ensuring human rights in the provision of contraceptive information and services.
      Consistent with previous research, our findings highlight important socioeconomic and racial/ethnic disparities in rates of preterm birth.
      • Hogue C.J.
      • Menon R.
      • Dunlop A.L.
      • Kramer M.R.
      Racial disparities in preterm birth rates and short inter-pregnancy interval: an overview.
      • Schempf A.H.
      • Branum A.M.
      • Lukacs S.L.
      • Schoendorf K.C.
      The contribution of preterm birth to the black-white infant mortality gap, 1990 and 2000.
      • MacDorman M.F.
      • Callaghan W.M.
      • Mathews T.J.
      • Hoyert D.L.
      • Kochanek K.D.
      Trends in preterm-related infant mortality by race and ethnicity, United States, 1999-2004.
      We found an increased odds of preterm birth for all non-white race/ethnicities, with the highest risk among black women. black women had >1.5 odds of a preterm birth than white women. Different hypotheses exist for the excess risk of preterm birth observed among black women compared with white women.

      Iams JD. Presidential address. American Gynecological and Obstetrical Society 32nd annual meeting; 2014. Available at: . http://www.agosonline.org/public/PDF/2013/11-iams.pdf. Accessed December 13, 2014.

      • Kim D.
      • Saada A.
      The social determinants of infant mortality and birth outcomes in Western developed nations: a cross-country systematic review.
      • Hogue C.J.
      • Menon R.
      • Dunlop A.L.
      • Kramer M.R.
      Racial disparities in preterm birth rates and short inter-pregnancy interval: an overview.
      • Kramer M.R.
      • Hogue C.J.
      • Dunlop A.L.
      • Menon R.
      Preconceptional stress and racial disparities in preterm birth: an overview.
      • Kramer M.R.
      • Hogue C.R.
      What causes racial disparities in very preterm birth? A biosocial perspective.
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      • Wilkins R.
      • Goulet L.
      • et al.
      Investigating socio-economic disparities in preterm birth: evidence for selective study participation and selection bias.
      Addressing racial and ethnic differences in contraceptive method choice is 1 strategy to mitigate this risk. Persistent racial and ethnic differences in contraceptive use in a program where all methods are covered for all users have been described.
      • Dehlendorf C.
      • Foster D.G.
      Thiel de Bocanegra H, Brindis C, Bradsberry M, Darney P. Race, ethnicity and differences in contraception among low-income women: methods received by Family PACT Clients, California, 2001-2007.
      These variations suggest that factors beyond socioeconomic status and health care access influence contraceptive use. An improved understanding of the reasons for these, such as client knowledge and preferences, is important, because differences by race and ethnicity in method choice may have an effect on racial and ethnic disparities in unintended pregnancy and preterm birth.
      • Dehlendorf C.
      • Foster D.G.
      Thiel de Bocanegra H, Brindis C, Bradsberry M, Darney P. Race, ethnicity and differences in contraception among low-income women: methods received by Family PACT Clients, California, 2001-2007.
      Our findings should be interpreted with the following limitations in mind. As in all observational research, our analysis is limited by variables captured in our data sources, the Birth Statistical Master Files and Medi-Cal or Family PACT claims data. We are unable to capture partner’s sterilization or contraception purchased independently by clients, such as condoms, which would not generate a pharmacy claim. Importantly, our data set does not include information on breast-feeding status or pregnancy intent, both of which may impact contraceptive use and fertility. Contraception use is a marker for pregnancy intention, which has been shown to be a risk factor for preterm birth.
      • Afable-Munsuz A.
      • Braveman P.
      Pregnancy intention and preterm birth: differential associations among a diverse population of women.
      This study focused on women who received publicly funded family planning services and were therefore <200% of the Federal Poverty Level at least temporarily during their 18-month postpartum period. As it is a young population, the proportion of women with higher education is lower than in the general US population. While the study reflects California demographics, it has a higher Hispanic population, an underrepresented black group, and a higher proportion of foreign-born individuals than the national average. To control for this, and allow our results to be generalizable to a broader US population, we adjusted for race/ethnicity, nativity, and education in our model. It is also important to note that our study focuses on the first 18 months postpartum. Other studies have suggested that the impact of interpregnancy interval on preterm birth nadirs at 20 months.
      • Conde-Agudelo A.
      • Rosas-Bermudez A.
      • Kafury-Goeta A.C.
      Effects of birth spacing on maternal health: a systematic review.
      Longer interpregnancy intervals may be associated with medical problems that result in lower fertility. Thus, it is possible that the benefit observed from postpartum contraception may be confounded with other variables and decrease over time. Lastly, using the probabilistic linkage methodology to link the birth file to the claims data, there is a very small percentage of error due to mismatch.
      Preterm birth is a common and costly health problem globally, and effective interventions to reduce rates of preterm birth are needed in both high- and low-resource settings. Our study provides evidence of the impact postpartum contraception provision has on reducing preterm birth. Postpartum contraception is a key strategy to improve maternal and neonatal health through prevention of unintended pregnancy, and subsequent reduction in morbidity and mortality. Efforts to improve access to high-quality contraceptive information and services are needed.

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