Table 4.

Selected Adjusted Stillbirth Odds Ratios for Smoking and Drug Use

Characteristic*	All Pregnancies		Nonanomalous, Singleton Pregnancies, Excluding Intrapartum Stillbirths
	Adjusted Odds Ratio (95% CI)	P	Adjusted Odds Ratio (95% CI)	P
Cotinine concentration (ng/ml), by median for positives
Negative (<0.25)†	reference	<.001	reference	<.001
Positive, ≤ 50th %tile (≤9.68)	2.05 (1.33, 3.17)		1.84 (1.11, 3.05)
Positive, > 50th %tile (>9.68)	2.56 (1.66, 3.93)		2.70 (1.72, 4.25)
Test: linear trend		<.001		<.001
Cotinine and drug use‡
Negative cotinine (<0.25)† & negative for all drugs	reference	<0.001	reference	<0.001
Positive cotinine & negative for all drugs	2.08 (1.31, 3.30)		2.46 (1.49, 4.04)
Negative cotinine (<0.25)† & positive for any drug	1.39 (0.59, 3.28)		1.89 (0.82, 4.40)
Positive cotinine & positive for any drug	4.53 (1.71, 12.05)		4.00 (1.45, 10.97)

CI, confidence interval.

^*Weighted stillbirth odds ratios and p-values are shown for smoking and drug use characteristics after adjustment for stillbirth risk factors known at pregnancy confirmation. The weights take into account the study design and differential consent based on characteristics recorded on all eligible pregnancies that were screened for the study. The adjustment for stillbirth risk factors is through a modified risk factor score for stillbirth developed on the logit scale using coefficients from a logistic regression model. The modification was to exclude coefficients associated with smoking status and illicit drug use. Weighted (unweighted) samples sizes for observations included in these adjusted analyses for cotinine are 548 (551) stillbirths and 1143 (1497) live births for all pregnancies and 367 (375) and 1094 (1410), respectively, for non-anomalous, singleton pregnancies, excluding intrapartum stillbirths. For cotinine and drug use, the sample sizes are 348 (359) and 708 (855), respectively, for all pregnancies and 246 (257) and 684 (811), respectively, for the subgroup. For ordered categories on cotinine levels, tests for linear and quadratic trends in the log odds of stillbirth were conducted using orthogonal contrasts. Neither of the quadratic trends was significant and their p-values are not reported.

^†Lower limit of detectability for the cotinine assay.

^‡The toxicology screening panel can detect amphetamines (amphetamine, e,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxy-N-ethylamphetamine (MDEA), N,N-dimethyldopamine (DMDA,) and methamphetamine), cannabinoids (carboxy-THC), cocaine (benzoylecgonine), opiates (codeine, hydrocodone, hydromorphine, morphine, 6-Monoacetylmorphine (6MAM), and meconin), phencyclidine (phencyclidine (PCP)), 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), methadone), and barbiturates (amobarbital, butalbital, pentobarbital, Phenobarbital, and secobarbital).