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Table 1 Total number of births and preterm births and prevalence of preterm birth (as a percentage) according to maternal characteristics and perinatal health behaviors in California from 2007 to 2016

From: Temporal trends, patterns, and predictors of preterm birth in California from 2007 to 2016, based on the obstetric estimate of gestational age

Year

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

Number of births

554,689

546,201

524,058

508,124

500,367

502,124

492,921

500,404

490,383

487,818

Number of preterm births

50,108

48,796

45,394

42,909

42,080

41,839

40,885

40,767

40,947

41,555

Percentage of preterm births

9.0

8.9

8.7

8.4

8.4

8.3

8.3

8.2

8.4

8.5

Variable

Maternal age (years)

  < 20

9.1

8.8

8.4

8.2

8.2

8.1

8.0

8.0

8.0

8.3

 20–24

8.1

8.0

7.7

7.6

7.4

7.4

7.4

7.1

7.5

7.7

 25–29

8.2

8.1

7.8

7.6

7.6

7.6

7.6

7.3

7.5

7.7

 30–34

9.0

8.9

8.6

8.4

8.4

8.3

8.1

8.0

8.2

8.2

 35–39

10.7

10.6

10.4

10.0

10.0

9.7

9.7

9.5

9.7

9.9

 40–54

14.2

14.4

14.1

13.5

13.6

13.3

13.2

13.2

13.5

13.6

Maternal race and ethnicity

 Hispanic

8.6

8.4

8.2

8.0

8.1

8.1

8.2

8.2

8.4

8.7

 Whitea

9.0

8.8

8.5

8.2

8.0

7.6

7.7

7.3

7.5

7.6

 Asianb

8.8

8.8

8.8

8.3

8.4

8.3

8.0

7.5

7.8

8.1

 Pacific Islanderc

10.7

10.3

9.4

10.3

8.6

8.8

8.9

9.1

10.8

9.6

 African American

12.7

13.0

12.3

12.2

11.7

11.9

11.6

11.9

11.7

11.4

 Multiple race

9.8

9.1

9.2

9.1

8.6

9.1

8.7

9.0

8.9

9.3

 American Indiand

10.4

10.6

9.3

10.0

8.8

8.8

10.0

8.9

10.1

10.3

 Other/unknowne

12.8

13.0

11.7

12.2

12.0

11.3

11.1

11.6

10.9

10.5

Maternal education level

 Less than high school diploma

8.8

8.7

8.5

8.3

8.4

8.4

8.7

9.0

9.3

9.5

 High school diploma

8.9

9.0

8.5

8.4

8.4

8.2

8.2

8.1

8.3

8.6

 Some college or associate degree

9.4

9.1

8.8

8.8

8.7

8.5

8.5

8.3

8.5

8.6

 Bachelor’s degree or higher

8.9

8.7

8.5

8.0

7.9

7.9

7.6

7.3

7.5

7.6

 Unknown

10.9

11.3

10.6

10.5

10.4

10.2

10.5

10.2

9.8

10.0

Maternal nativity

 Foreign-born

8.2

8.2

8.0

7.8

8.0

7.9

7.9

7.8

8.1

8.4

 United States-born

9.7

9.5

9.1

8.9

8.7

8.6

8.5

8.3

8.5

8.6

Maternal demographic region

 Central Coast

8.1

8.1

7.7

7.7

7.7

7.4

7.8

7.4

7.9

7.9

 Greater Bay Area

8.5

8.6

8.6

8.4

8.1

8.4

8.2

7.9

8.1

8.3

 Inland Empire

9.5

9.0

8.9

8.6

8.4

8.7

8.5

8.3

8.5

8.8

 Los Angeles County

9.3

9.3

8.8

8.6

8.7

8.5

8.5

8.4

8.7

8.8

 Northern and Sierra

8.4

8.0

7.6

7.4

7.6

7.5

7.7

7.4

8.0

8.1

 Orange County

8.7

8.3

8.5

8.1

8.2

7.8

7.6

7.3

7.5

7.9

 Sacramento area

8.8

8.5

8.3

8.2

8.1

8.0

7.9

8.1

8.0

8.1

 San Diego area

9.5

9.0

9.0

8.4

8.4

8.3

8.1

8.2

8.0

8.4

 San Joaquin Valley

9.4

9.7

9.1

8.9

9.0

8.8

8.9

8.8

9.0

9.0

Source of prenatal care payment

 Private

9.2

9.0

8.8

8.7

8.5

8.4

8.2

8.1

8.2

8.3

 Medi-Cal

8.7

8.6

8.3

8.1

8.1

8.2

8.3

8.2

8.5

8.7

WIC Participation

 No

9.5

9.4

9.1

8.9

8.7

8.6

8.4

8.1

8.3

8.4

 Yes

8.6

8.5

8.3

8.0

8.2

8.1

8.2

8.2

8.4

8.6

First trimester prenatal care initiation

 No

9.1

8.6

8.3

8.3

8.2

8.2

8.2

8.1

8.2

8.5

 Yes

8.9

8.9

8.6

8.4

8.4

8.3

8.2

8.1

8.3

8.4

Parity

 Primiparous

8.4

8.2

8.0

7.8

7.7

7.7

7.7

7.4

7.7

7.8

 Multiparous (2–5)

9.3

9.2

8.9

8.7

8.6

8.5

8.4

8.4

8.5

8.7

 Multiparous (6–12)

14.9

15.2

15.0

14.6

13.9

14.6

14.7

15.3

15.3

15.6

Plurality

 Singleton births

8.0

7.9

7.5

7.4

7.3

7.3

7.2

7.1

7.3

7.5

 Multiple births

60.9

59.2

59.0

57.4

57.4

56.0

55.0

54.4

55.8

56.8

Maternal smoking during both first and second trimesters

 No

8.9

8.8

8.6

8.4

8.3

8.2

8.2

8.1

8.2

8.4

 Yes

15.7

15.0

14.6

14.2

14.8

15.6

16.4

15.5

16.9

17.9

Prepregnancy body mass index (kg/m2)

 Underweight (≤18.5)

9.7

10.0

9.4

9.0

8.9

8.8

8.6

8.5

8.4

8.7

 Normal (18.5–24.9)

8.5

8.4

8.1

7.9

7.9

7.7

7.7

7.4

7.5

7.7

 Overweight (25.0–29.9)

8.8

8.5

8.3

8.1

8.3

8.2

8.1

8.1

8.2

8.6

 Obese I (30.0–34.9)

9.6

9.3

9.1

9.0

8.9

8.8

8.9

9.0

9.3

9.3

 Obese II (35.0–39.9)

10.1

10.1

10.4

9.4

9.1

10.1

9.4

9.6

10.1

10.1

 Obese III (≥ 40)

10.8

11.2

10.0

11.2

10.3

10.1

10.4

10.0

10.6

10.4

  1. All live births were delivered at 17–47 completed weeks of gestation based on obstetric estimates and birthweight of ≥500 g at birth. Births with missing information on gestational age or birthweight were excluded
  2. Total number of births = 5,107,089
  3. Race/ethnicity results were tabulated using the following race/ethnic groups: Hispanic, White, Asian/ Pacific Islander, African American, Multiple race (two or more races), American Indian, and other
  4. Hispanic origin was determined first and could include any race group. Next, members of the two or more races group were identified and are not reported in the single-race groups. To remain consistent with the population data obtained from the California Department of Finance, the single-race groups are defined as follows:
  5. a“White” race group includes White women
  6. b“Asian” race group includes Asian Indian, Asian (specified/unspecified), Cambodian, Chinese, Filipino, Hmong, Japanese, Korean, Laotian, Thai, and Vietnamese women
  7. c“Pacific Islander” race group includes Guamanian, Hawaiian, Samoan, and other Pacific Islander women
  8. d“American Indian” race group includes Aleutian, American Indians, and Eskimo women
  9. e“Other/unknown” includes not stated or unknown
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Maternal Health, Neonatology and Perinatology

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