The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families (1995)
Chapter: D Table of Odds Ratios
D Tables of Odds Ratios: Supplement to Chapter 3
Carol J.R. Hogue
Member, Committee on Unintended Pregnancy
Chapter 3 includes an assessment of the literature published within the last 30 years that addresses various health and health-related consequences of unintended pregnancy. The literature base for most consequences studied does not permit a numerical survey. However, some effects, particularly ones related to pregnancy and pregnancy outcome, have been studied sufficiently to permit a structured assessment. These consequences include timing of the initiation of prenatal care, an estimate of the adequacy of prenatal care based on both timing and the number of visits, exposure of the fetus to smoking and alcohol, and the incidence of low birthweight (<2,500 grams) among live-born infants. A graphical presentation of studies on these issues is provided in Chapter 3.
This appendix provides more detail regarding those studies. To be included in this structured assessment, an investigation had to compare outcomes between women reporting intended conceptions and women reporting unintended conceptions, variously defined. When unintended was subdivided into mistimed and unwanted, estimates of effects (usually odds ratios) are included for both categories of unintended conception. An odds ratio is an estimate of the relative risk, that is, the risk of a poor outcome among the "exposed" group (unintended conception) relative to the risk of a poor outcome among the "unexposed" group (intended conceptions). These results, with 95 percent confidence intervals, are shown in column 5 of the tables in this appendix. The results in Figures 3-3 through 3-5 of Chapter 3 were selected from these results. If a study calculated both a crude and an adjusted odds ratio, only the adjusted one was included in the figure. When the results were available for both mistimed and unwanted conceptions, they were included in the figures. The references for this appendix are provided in Chapter 3.
TABLE D-1 Studies of Prenatal Care Attainment Associated with Pregnancy Intention
|
Definition of Intention |
Population/Sample |
Retrospective/Prospective |
Control Factors |
Results |
Reference/Comments |
|
Initiation of Prenatal Care (PNC) after the First Trimester |
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|
|
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|
Unwanted: (a) at conception, (b) at fourth month, (c) in last trimester |
120 black women, Boston City Hospital, married with at least one living child, 1964 |
Prospective at three points during gestation |
None |
Late PNC, (a) ORa = 2.89 (0.96,9.02)c, (b) OR = 3.57 (1.38,9.36)c , (c) OR = 2.42 (0.65,9.31)c |
Watkins, 1968; (a) 77.5%, (b) 27.9%, (c) 11.7% |
|
(a) Mistimed, (b) unwanted |
NSFG, 1982 (random sample of U.S. women 15–44, with live births 1979–1982) |
Retrospective (œ3 yrs. postpartum) |
Race |
(a) RRb, all = 1.6c; RR, white = 1.6c; RR, black = 1.4c (b) RR, all = 1.8c; RR, white = 1.7c; RR, black = 1.75c |
Pamuk and Mosher, 1988 |
|
"Intended" vs. "unintended" |
NNS, 1980 (random sample of U.S., married) |
Retrospective (>6 mo postpartum) |
Race, residence, education, birth order |
Wells et al., 1987 |
|
|
Planned vs. unplanned |
416, central Harlem residents in PNC, 1982–1983 |
Retrospective (at first PNC visit) |
None |
OR = 1.31c |
McCormick et al., 1987; 73% were unplanned |
|
Definition of Intention |
Population/Sample |
Retrospective/Prospective |
Control Factors |
Results |
Reference/Comments |
|
Intended (stopped using contraception because of pregnancy desire or just before pregnancy, wanted to become pregnant) vs. unintended |
NLSY, 1984, women 18–26, nationally representative sample of 6,015 |
Retrospective (78%), prospective (22% during pregnancy) |
Race, economically disadvantaged (white), southern or urban resident at age 14, grandmother's education, maternal age |
Marsiglio and Mott, 1988; they used the term "wanted" but the questions more closely reflect intended |
|
|
"Intended" vs. "unintended" |
Random sample, 1,490; births in England, 1,984 |
Retrospective (>4 mo postpartum) |
None |
Risk of entry after first trimester; OR = 1.9 (1.33,2.17)c |
Cartwright, 1988; interview asked pregnancy intention |
|
(a) Mistimed, (b) unwanted |
NMIHS, 1988 nationally representative sample of 9,953 |
Retrospective (at least 1 yr postpartum) |
None |
Kost et al., 1994 |
|
|
(a) Mistimed, (b) unwanted |
Oklahoma PRAMS, 1988–1993, (a) N = 2,329 (b) N = 933 |
Retrospective (4–12 mo postpartum) |
Age, education, source of family income, timing of pregnancy recognition, parity |
(a) Crude OR = 2.7 (2.1,3.4); adjusted OR = 1.4 (1.04,1.9) (b) crude OR = 4.6 (1.3,6.1); adjusted OR = 1.7 (1.1,2.5) |
DePersio et al., 1994 |
|
Planned vs. "surprise" |
Hispanic, Houston, TX, public hospital patients, 100 each entered PNC in 1st, 2nd, 3rd trimester or none |
Retrospective (at delivery) |
None |
Risk of entry after first trimester OR = 2.64 (1.50,4.66)c |
Byrd, 1994; early PNC associated with hospital access card, fewer perceived barriers, more benefits to baby |
|
Inadequate Prenatal Care (PNC) |
|
|
|
|
|
|
See Results column |
Random sample in Oklahoma, births, 1985 |
Retrospective (at delivery) |
Multiple |
Receipt of inadequate care, mistimed, family support OR = 1.15c (NS); mistimed, pregnancy discussed OR = 1.09c (NS); unwanted, family support, OR = 1.15c (NS); unwanted, pregnancy discussed, OR = 1.36 (p < 0.05) |
St. John and Winston, 1989; see text |
|
Unwanted |
Case—control study, three sites in Missouri; adequate, N=720; inadequate, N=764 |
Retrospective (at delivery) |
Multiple |
Receipt of inadequate care; OR = 1.39 (1.11, 1.67) |
Sable, 1992; 74% of women with inadequate care had not wanted the pregnancy |
|
Definition of Intention |
Population/Sample |
Retrospective/Prospective |
Control Factors |
Results |
Reference/Comments |
|
Initial attitude: negative, mixed, or positive |
200 poor, mainly black women, Detroit, MI |
Retrospective (at delivery) |
Attitudinal |
Zero-order correlation = 0.39 (p < 0.05) |
Poland et al., 1990 |
|
Planned vs. unplanned; somewhat/very unhappy vs. neutral/happy |
Case—control, 400 inadequate care, 100 adequate care, Mecklenburg, NC, 1990–991 |
Retrospective (at delivery) |
None |
For unplanned, OR = 1.86 (1.10,3.18)c for unhappy, OR = 2.2 (0.96,3.70)c |
Boggs and Miles, 1991; among cases with inadequate care, 81% unplanned and 21.2% unhappy |
|
(a) Mistimed, (b) unwanted |
Oklahoma PRAMS, 1988–1993 (a) N = 2,092 (b) N = 810 |
Retrospective (4–12 mo postpartum) |
Education, marital status, source of family income, timing of pregnancy initiation, parity |
(a) crude OR = 2.7 (1.9,3.7); adjusted OR = 1.3 (0.8,1.9) (b) crude OR = 5.5 (3.8,8.0); adjusted OR = 1.9 (1.2,3.1) |
DePersio et al., 1994 |
|
NOTE: NSFG (National Survey of Family Growth); NNS (National Natality Survey); NLSY (National Longitudinal Survey of Youth); NMIHS (National Maternal and Infant Health Survey); PRAMS (Pregnancy Risk Assessment Monitoring System); NS (not significant). |
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|
a |
The OR (odds ratio) is the odds of adverse outcome among exposed persons relative to the odds among unexposed persons. |
|
b |
The RR (relative risk) is the risk of the adverse outcome among exposed persons relative to the risk among unexposed persons. Relative risk and odds ratios are similar when adverse outcome is rare. |
|
c |
Calculated for this report. |
TABLE D-2 Studies of Behavioral Risk Factors for Low Birthweight or Preterm Delivery Associated with Pregnancy Intention
|
Definition of Intention |
Population/Sample |
Retrospective/Prospective |
Control Factors |
Results |
Reference/Comments |
|
Smoking |
|
|
|
|
|
|
''Intended" vs. "unintended" |
NNS, 1980 (random sample of U.S. married women) |
Retrospective (> 6 mo post-partum) |
Race, residence, education, birth order, early PNC |
Whether didn't stop smoking: crude ORa = 1.13c; adjusted OR = 1.07c |
Wells et al., 1987; early PNC had similar but independent impact on smoking cessation, as planning the pregnancy did |
|
Planned vs. unplanned |
416, central Harlem residents in PNC, 1982–1983 |
Retrospective (at first PNC visit) |
None |
OR = 1.08c |
McCormick et al., 1987; 41% smoked during pregnancy |
|
(a) Mistimed, (b) unwanted |
NSFG, 1982 (random sample of U.S. women ages 15–44, with live births 1979–1982) |
Retrospective (3 yr postpartum) |
Race |
(a) RRb, all = 1.3c RR, white = 1.25c RR, black = 1.05c (b) RR, all = 1.3c RR, white = 1.4c RR, black = 1.2c |
Pamuk and Mosher, 1988 |
|
Definition of Intention |
Population/Sample |
Retrospective/Prospective |
Control Factors |
Results |
Reference/Comments |
|
"Intended" vs. "unintended" |
Random sample, 1,490; births in England, 1,984 |
retrospective (>4 mo postpartum) |
Social class |
Smoking OR = 1.66 (1.25,2.22)c |
Cartwright, 1988; interview asked pregnancy intention |
|
Intended (stopped using contraception because of pregnancy desire or just before pregnancy, wanted to become pregnant) vs. unintended |
NLSY, 1984, women 18–26, nationally representative sample of 6,015 |
Retrospective (78%) and prospective (22% during pregnancy) |
Race, economically disadvantaged (white), southern or urban resident at age 14, grandmother's education, maternal age |
Marsiglio and Mott, 1988; they used the term "wanted" but the questions more closely reflect intended |
|
|
(a) Mistimed, (b) unwanted |
NMIHS, 1988, nationally representative sample of 9,953 |
Retrospective (at least 1 yr postpartum) |
Marital status |
Kost et al., 1994; smoked during pregnancy; married women with wanted conception smoked much less than other subgroups |
|
|
(a) Mistimed, (b) unwanted |
Oklahoma PRAMS, 1988–1993 (a) N = 2,267 (b) N = 900 |
Retrospective (4-12 mo postpartum) |
Age, education, race, martial status, source of family income |
(a) Crude OR = 1.3 (1.02, 1.6); adjusted OR = 1.0 (0.8,1.3) (b) crude OR = 2.4 (1.9, 3.1); adjusted OR = 1.8 (1.3,2.4) |
DePersio et al., 1994; smoking 3 mo before delivery |
|
Alcohol |
|
|
|
|
|
|
Planned vs. unplanned |
416, central Harlem residents in PNC, 1982–1983 |
Retrospective (at first PNC visit) |
None |
OR = 2.67c |
McCormick et al., 1987; 9.2% drank during pregnancy |
|
Definition of Intention |
Population/Sample |
Retrospective/Prospective |
Control Factors |
Results |
Reference/Comments |
|
Intended (stopped using contraception because of pregnancy desire or just before pregnancy, wanted to become pregnant) vs. unintended |
NLSY, 1984, women aged 18-26, nationally representative sample of 6,015 |
Retrospective (78%), prospective (22% during pregnancy) |
Race, economically disadvantaged (white), southern or urban residents at age 14, grandmother's education, maternal age |
Marsiglio and Mott, 1988; they used the term "wanted," but the questions more closely reflect intended |
|
|
(a) Mistimed, (b) unwanted |
NMIHS, 1988, nationally representative sample of 9,953 |
Retrospective (at least 1 yr postpartum) |
None |
(a) RR = 1.11c (b) RR = 1.77c |
Kost et al., 1994; drank one or more times per week |
|
NOTE: NNS (National Natality Survey); NSFG (National Survey of Family Growth); NLSY (National Longitudinal Survey of Youth); PRAMS (Pregnancy Risk Assessment Monitoring System); NMIHS (National Maternal and Infant Health Survey). |
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|
a |
The OR (odds ratio) is the odds of adverse outcome among exposed persons relative to the odds among unexposed persons. |
|
b |
The RR (relative risk) is the risk of the adverse outcome among exposed persons relative to the risk among unexposed persons. Relative risk and odds ratios are similar when adverse outcome is rare. |
|
c |
Calculated for this report. |
TABLE D-3 Studies of Low Birth Weight (LBW) (<2,500 grams) Associated with Pregnancy Intention
|
Definition of Intention |
Population/Sample |
Retrospective/ Prospective |
Control Factors |
Results |
Reference/ Comments |
||
|
Wanted vs. unwanted |
17 selected U.S. sites, 1971–1972; 4,891 white and 3,030 black women |
Retrospective (at delivery) |
Race |
Crude ORa = 1.2c OR for whites = 1.36c OR for blacks = 0.94c |
Morris et al., 1973; women with high education and unwanted conceptions had babies with significantly higher LBW rates |
||
|
Intended (stopped using contraception because of pregnancy desire or just before pregnancy, wanted to become pregnant) vs. unintended |
NLSY, 1984, women ages 18–26, nationally representative sample of 6,015 |
Retrospective (78%) and prospective (22% during pregnancy) |
Race, economically disadvantaged (white), southern or urban resident at age 14, grandmother's education, maternal age |
For unintended, crude RRb = 1.3c; adjusted OR = 0.92c adjusted OR = 0.88c (including behavioral risk factors) |
Marsiglio and Mott, 1988 |
||
|
(a) Mistimed, (b) unwanted |
NSFG, 1982 (random sample of U.S. women aged 15–44, with live births 1979–1982) |
Retrospective (œ 3 yr post-partum) |
Race |
Pamuk and Mosher, 1988 |
|||
|
Definition of Intention |
Population/Sample |
Retrospective/ Prospective |
Control Factors |
Results |
Reference/ Comments |
||
|
Unintended vs. intended |
Case-control study, 1984; 83 LBW cases, 1,392 NBW controls |
Retrospective (at delivery) |
Smoking |
Cartwright, 1988 |
|||
|
Wanted vs. unwanted |
1,518 multiparous, indigent women in Birmingham, AL, 1985–1988, with risk of IUGR |
Prospective (at PNC visit) |
None |
OR = 1.3c |
Goldenberg et al., 1991; sample was limited to women receiving early PNC |
||
|
Mistimed, unwanted |
1988 NSFG, most recent singleton birth |
Retrospective (< 5 yr post-partum) |
Smoking, race |
Reduction in LBW if all unwanted conceptions had been avoided |
Kendrick et al., 1990; mistimed not associated with LBW |
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|
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|
No. |
% change |
|
|
|
|
|
|
Black |
69,000 |
7 |
|
|
|
|
|
|
White |
67,000 |
4 |
|
|
|
|
|
|
Smoker |
70,000 |
6 |
|
|
|
|
|
|
Non- smoker |
66,000 |
7 |
|
|
(a) Mistimed, (b) unwanted |
NMIHS, 1988, nationally representative sample of 9,953 |
Retrospective (at least 1 yr postpartum) |
None |
(a) Crude RR = 1.21c (b) crude RR = 1.80c |
Kost et al., 1994 |
||
|
(a) Mistimed, (b) unwanted |
Oklahoma PRAMS, 1988–1993 (a) N = 2,215 (b) N = 888 |
Retrospective (4–12 mo postpartum) |
Education, black race, marital status at delivery, smoking three months before delivery, trimester that PNC began, infant gender, parity, plurality |
(a) Crude OR = 1.2 (1.1,1.4); adjusted OR = 1.0 (0.8,1.1) (b) crude OR = 1.4 (1.2,1.6); adjusted OR = 0.9 (0.7,1.1) |
DePersio et al., 1994 |
||
|
(a) Mistimed, (b) unwanted |
1990 NICHD/MOMIH survey |
Retrospective (>6 mo postpartum) |
Multiple |
(a) No increased risk (b) crude OR = 1.44 for LBW adjusted or NS VLBW not associated |
Sable, 1992 |
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NOTE: NLSY (National Longitudinal Survey of Youth); NBW (Normal birthweight is over 2,500 grams); IUGR (intrauterine growth retardation); NSFG (National Survey of Family Growth); NMIHS (National Maternal and Infant Health Survey); PRAMS (Pregnancy Risk Assessment Monitoring System); NICHD/MOMIH (National Institute of Child Health and Development/Missouri Mothers and Infant Health); VLBW (very low birthweight is under 1,500 grams) |
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|
a |
The OR (odds ratio) is the odds of adverse outcome among exposed persons relative to the odds among unexposed persons. |
|
b |
The RR (relative risk) is the risk of the adverse outcome among exposed persons relative to the risk among unexposed persons. Relative risk and odds ratios are similar when adverse outcome is rare. |
|
c |
Calculated for this report. |
