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Which Risks Are Most Significant Predictors of SGA Births?



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Am Fam Physician. 2001 Dec 1;64(11):1892-1896.

Although many maternal risk factors have been identified as indicators of poor pregnancy outcomes such as small-for-gestational-age (SGA) infants, the magnitude of these risks has not been well quantified, and little is known about the ways multiple risk factors interact with one another. Ahluwalia and colleagues studied data on SGA infants born in 13 states during 1997 to clarify the magnitude of individual and combined maternal risk factors.

The authors used data from the on-going national Pregnancy Risk Assessment Monitoring System that surveys mothers after birth and links these data to information about the pregnancy, birth and infant. In selecting states with high rates of survey completion, the researchers considered more than 19,000 births. The survey included questions about demographics, family, financial and personal information, maternal lifestyle issues such as stress, working patterns, alcohol, tobacco and drug use, and information on maternal health and pregnancy issues. Information on infants was primarily obtained from the birth certificates.

Most mothers were 20 to 34 years of age, married and multiparous, and had completed at least a high-school education. Approximately 77 percent were white and 19 percent black. Almost 40 percent were enrolled in Medicaid programs. As shown in the accompanying table, 45 percent of the pregnancies were unintended, 14 percent of the mothers smoked and 23 percent entered prenatal care after the first trimester or had no prenatal care. Levels of trauma and financial or emotional stress were significant.

Overall, 3.2 percent of infants were SGA at birth. The most significant individual risk factor was smoking, followed by low weight gain during pregnancy, little or no prenatal care, and traumatic stress. Only 10 percent of mothers had no risk factors, and many women had multiple risk factors. The percentage of SGA births was directly associated with the number of risks, rising from 1.6 percent for no risk factors to 6.4 percent for six or more risk factors.

Lifestyle and Psychosocial Characteristics of Women Delivering a Live Infant

Lifestyle and psychosocial characteristics n Percentage Standard error Crude OR of delivering an SGA infant (95% CI)

Maternal smoking

Yes

3,002

13.7

0.5

3.27 (2.45, 4.36)

No

15,555

86.3

0.5

Reference

Maternal alcohol use

Yes

952

5.9

0.3

1.03 (0.71, 1.50)

No

18,009

94.1

0.3

Reference

Weight gain for BMI*

<Recommended

6,913

30.5

0.6

1.96 (1.48, 2.60)

Amount recommended

5,018

32.1

0.6

Reference

>Recommended

5,663

37.4

0.6

0.72 (0.54–0.96)

Entry into prenatal care

First trimester

14,311

77.4

0.5

Reference

>First trimester or none

4,651

22.7

0.5

1.55 (1.17, 2.05)

Pregnancy status

Unintended

8,076

44.5

0.6

1.25 (0.99, 1.58)

Intended

9,779

55.5

0.6

Reference

Experienced physical violence during pregnancy

Yes

950

4.5

0.3

1.16 (0.77, 1.76)

No

18,097

95.5

0.3

Reference

Experienced partner-associated stress

Yes

7,666

38.2

0.6

1.19 (0.96, 1.47)

No

11,484

61.8

0.6

Reference

Experienced emotional stress

Yes

7,064

35.6

0.6

1.06 (0.84, 1.32)

No

12,100

64.4

0.6

Reference

Experienced traumatic stress

Yes

4,605

22.5

0.5

1.66 (1.27, 2.17)

No

14,541

77.5

0.5

Reference

Experienced financial stress

Yes

11,149

57.2

0.6

1.11 (0.88, 1.41)

No

8,019

42.8

0.6

Reference


OR = odds ratio; SGA = small for gestational age; CI = confidence interval; BMI = body mass index.

*—BMI is defined as weight/height2. Appropriate weight gain for each BMI was categorized according to Institute of Medicine guidelines.

Reprinted with permission from Ahluwalia IB, Merritt R, Beck LF, Rogers M. Multiple lifestyle and psychosocial risks and delivery of small for gestational age infants. Obstet Gynecol 2001;97:652.

Lifestyle and Psychosocial Characteristics of Women Delivering a Live Infant

View Table

Lifestyle and Psychosocial Characteristics of Women Delivering a Live Infant

Lifestyle and psychosocial characteristics n Percentage Standard error Crude OR of delivering an SGA infant (95% CI)

Maternal smoking

Yes

3,002

13.7

0.5

3.27 (2.45, 4.36)

No

15,555

86.3

0.5

Reference

Maternal alcohol use

Yes

952

5.9

0.3

1.03 (0.71, 1.50)

No

18,009

94.1

0.3

Reference

Weight gain for BMI*

<Recommended

6,913

30.5

0.6

1.96 (1.48, 2.60)

Amount recommended

5,018

32.1

0.6

Reference

>Recommended

5,663

37.4

0.6

0.72 (0.54–0.96)

Entry into prenatal care

First trimester

14,311

77.4

0.5

Reference

>First trimester or none

4,651

22.7

0.5

1.55 (1.17, 2.05)

Pregnancy status

Unintended

8,076

44.5

0.6

1.25 (0.99, 1.58)

Intended

9,779

55.5

0.6

Reference

Experienced physical violence during pregnancy

Yes

950

4.5

0.3

1.16 (0.77, 1.76)

No

18,097

95.5

0.3

Reference

Experienced partner-associated stress

Yes

7,666

38.2

0.6

1.19 (0.96, 1.47)

No

11,484

61.8

0.6

Reference

Experienced emotional stress

Yes

7,064

35.6

0.6

1.06 (0.84, 1.32)

No

12,100

64.4

0.6

Reference

Experienced traumatic stress

Yes

4,605

22.5

0.5

1.66 (1.27, 2.17)

No

14,541

77.5

0.5

Reference

Experienced financial stress

Yes

11,149

57.2

0.6

1.11 (0.88, 1.41)

No

8,019

42.8

0.6

Reference


OR = odds ratio; SGA = small for gestational age; CI = confidence interval; BMI = body mass index.

*—BMI is defined as weight/height2. Appropriate weight gain for each BMI was categorized according to Institute of Medicine guidelines.

Reprinted with permission from Ahluwalia IB, Merritt R, Beck LF, Rogers M. Multiple lifestyle and psychosocial risks and delivery of small for gestational age infants. Obstet Gynecol 2001;97:652.

The authors conclude that a high percentage of pregnant mothers have multiple risk factors and that delivery of an SGA infant is directly associated with the number of those risk factors. They urge health care providers to be alert to risky behaviors and other factors in pregnant women that could place the infant at risk.

Ahluwalia IB, et al. Multiple lifestyle and psychosocial risks and delivery of small for gestational age infants. Obstet Gynecol. May 2001;97:649–56.

editor's note: In this large, unselected sample of pregnant mothers, only 10 percent had no risk factors, 45 percent reported that the pregnancy was unintended and 28 percent experienced trauma. These statistics are frightening, and the risk factors are likely to be underreported because these topics are confidential. We might assume that pregnancy is a healthy and joyful time, but for many women it is not. Even more distressing is that so many of the risks result from personal behavior choices. Physicians need to be more alert for risk factors in pregnant women and more effective in our interventions.—a.d.w.

 


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