AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 7, NUMBER 1
January 1990
MARIJUANA USE IN PREGNANCY AND PREGNANCY OUTCOME Frank R. Witter, M.D., and Jennifer R. Niebyl, M.D.*
ABSTRACT
Marijuana is a frequently used illicit recreational drug. It has been estimated that 14% of women between the ages of 18 and 25 years in the general population use marijuana.1 Because of the frequency of use, concern has arisen as to the possible effect on pregnancy. Previous reports have shown a correlation between marijuana use and poor fetal outcome as indicated by lower birthweight, shorter body length, smaller head circumference, and increased incidence of infants with dysmorphic features.2 The presence of meconium staining has also been reported to increase with marijuana use,3 whereas the length of gestation has been reported to decrease.4 This report summarizes our experience over a 3-year period with marijuana use in pregnancy. MATERIALS AND METHODS
As part of our standard prenatal history, all patients registered at the Johns Hopkins Hospital are asked about alcohol, tobacco, and other drug use during their pregnancy. Marijuana is one of the drugs specifically inquired about. This information is recorded in our computerized data base. A retrospective analysis of our data from 1983 through 1985 inclusive was conducted. Of 8350 records searched, 417 patients were identified who used marijuana but no other illicit drugs. The preg-
nancy outcomes of these patients were compared with the remaining 7933 patients who comprised the rest of the population. Statistical analysis was performed utilizing the Statistical Analysis System (SAS).5 The t test was utilized for continuous variables, whereas the chisquare test was used for noncontinuous variables. Statistical significance was taken to be a p value of 0.05 or less. The Bonferroni inequality was used to adjust for multiple comparisons. RESULTS
Table 1 lists the results of our initial comparison. Because of the known association between birthweight and race, the groups were stratified for race. Tables 2 and 3 present the data for all variables where a significant difference was found in the initial analysis. No additional significant differences were determined. As can be seen from Table 1, there was no significant association between marijuana use and total congenital anomalies. When the anomalies were broken down into classes, no significant association between marijuana use and congenital anomalies was found in any class. The classes were central nervous system, musculoskeletal, genitourinary, gastrointestinal, cardiovascular, respiratory, integument, dysmorphic, and multiple.
The Johns Hopkins University School of Medicine, Department of Gynecology and Obstetrics, Division of Maternal-Fetal Medicine, Baltimore, Maryland *Present address: Professor & Head, Department of Ob/Gyn, The University of Iowa Hospitals & Clinics, Iowa City, IA 52242 Reprint requests: Dr. Witter, The Johns Hopkins University School of Medicine, Department of Gynecology and Obstetrics, Division of Maternal-Fetal Medicine, 600 North Wolfe Street, Baltimore, MD 21205 Copyright © 1990 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
Downloaded by: National University of Singapore. Copyrighted material.
A retrospective analysis utilizing historical data collected as part of our computerized data base was performed to assess the impact of marijuana use in pregnancy on pregnancy outcome. Records of 8350 patients were reviewed and 417 patients gave a history of only marijuana use for a prevalence of 5%. There was no association between marijuana use and prematurity or congenital anomalies. Marijuana use was strongly associated with the use of alcoholic beverages and smoking. Previously reported associations may represent the concomitant use of these other drugs.
MARIJUANA USE IN PREGNANCY/Witter, Niebyl Table 1. Outcome Versus Marijuana Use User
Nonuser
2991 ± 687* 29.4 ± 14.5* 594 ± 392* 24.0 17.8% 19.4% 84.4% 78.4%
3110 ± 755* 31.2 ± 14.8* 611 ± 457* 19.8 15.9% 17.1% 67.3% 37.5%
48.0% 5.3% 21.3% 1.2% 6.5% 5.52% 23.7% 7.7%
30.6% 0.9% 14.9% 0.9% 5.5% 4.59% 21.2% 9.8%
0.0192+ NS+ NS+ NS* NS* NS*
0.0032* 0.0032* 0.0032* 0.0128* NS* NS* NS* NS*
NS*
*Mean ± SD. t test. *Chi-square test. +
Table 2. Outcome Versus Marijuana Use for Whites Mean birthweight (gm) Smokers Alcohol consumption Social Heavy Anemia
User
Nonuser
P
3158 ± 673*
3247 ± 811*
NS+
80%
32.9%
0.0032*
69.2% 6.2% 3.1%
43%
0 0032*
0.2% 4.6%
NS*
*Mean ± SD. t test. *Chi-square test.
+
Table 3. Outcome Versus Marijuana Use for Nonwhites Mean birthweight (gm) Smokers Alcohol consumption Social Heavy Anemia
User 2960 ± 686*
Nonuser 3045 ± 717*
NS+
79.3%
37.2%
0.0032*
44.0% 5.1% 24.7%
24.6% 1.2% 19.9%
0.0032*
*Mean ± SD. f t test. *Chi-square test.
P
NS*
DISCUSSION
Prevalence of marijuana use in our population is 6% with a prevalence of marijuana use exclusive of other illicit drugs of 5%. This is somewhat below the estimate for women 18 to 25 years of age of 14%.* The estimate of use for persons 18 to 25 years of age may be high for our population or there may have been some underreporting among our patients. Although increased meconium staining has been reported with marijuana use,3 we found no difference in the incidence of meconium staining between marijuana users and nonusers. Furthermore, we found no increase in fetal distress in labor or perinatal mortality. Marijuana has been reported to decrease the length of gestation;4 however, we found no increase in prematurity in marijuana users when measured by percentage of infants with birthweights less than 2500 gm or by percentage of infants delivered at less than 37 weeks' gestation. An increased incidence of anemia appears to be associated with race rather than with marijuana use, for when stratified for race this association is no longer statistically significant. The highly significant difference between marijuana users and nonusers for cigarette smoking, alcohol use, and race may explain some of the associations seen in the past that were not seen in our study. Although lower birthweight has been reported with marijuana use and we saw such an effect in our nonstratified data, much of the difference is due to the racial difference between the users and nonusers. When stratified for race, the association was no longer statistically significant. We found no association between marijuana use and fetal anomalies either in general or in specific groups. Because of the strong association with alcohol use that we have seen, we believe that the previous report on the increased incidence of infants
Downloaded by: National University of Singapore. Copyrighted material.
Mean birth weight (gm) Weight gain (lbs) Duration of labor (min) Perinatal mortality (per 1000) Birthweight
January 1990
MARIJUANA USE IN PREGNANCY AND PREGNANCY OUTCOME Frank R. Witter, M.D., and Jennifer R. Niebyl, M.D.*
ABSTRACT
Marijuana is a frequently used illicit recreational drug. It has been estimated that 14% of women between the ages of 18 and 25 years in the general population use marijuana.1 Because of the frequency of use, concern has arisen as to the possible effect on pregnancy. Previous reports have shown a correlation between marijuana use and poor fetal outcome as indicated by lower birthweight, shorter body length, smaller head circumference, and increased incidence of infants with dysmorphic features.2 The presence of meconium staining has also been reported to increase with marijuana use,3 whereas the length of gestation has been reported to decrease.4 This report summarizes our experience over a 3-year period with marijuana use in pregnancy. MATERIALS AND METHODS
As part of our standard prenatal history, all patients registered at the Johns Hopkins Hospital are asked about alcohol, tobacco, and other drug use during their pregnancy. Marijuana is one of the drugs specifically inquired about. This information is recorded in our computerized data base. A retrospective analysis of our data from 1983 through 1985 inclusive was conducted. Of 8350 records searched, 417 patients were identified who used marijuana but no other illicit drugs. The preg-
nancy outcomes of these patients were compared with the remaining 7933 patients who comprised the rest of the population. Statistical analysis was performed utilizing the Statistical Analysis System (SAS).5 The t test was utilized for continuous variables, whereas the chisquare test was used for noncontinuous variables. Statistical significance was taken to be a p value of 0.05 or less. The Bonferroni inequality was used to adjust for multiple comparisons. RESULTS
Table 1 lists the results of our initial comparison. Because of the known association between birthweight and race, the groups were stratified for race. Tables 2 and 3 present the data for all variables where a significant difference was found in the initial analysis. No additional significant differences were determined. As can be seen from Table 1, there was no significant association between marijuana use and total congenital anomalies. When the anomalies were broken down into classes, no significant association between marijuana use and congenital anomalies was found in any class. The classes were central nervous system, musculoskeletal, genitourinary, gastrointestinal, cardiovascular, respiratory, integument, dysmorphic, and multiple.
The Johns Hopkins University School of Medicine, Department of Gynecology and Obstetrics, Division of Maternal-Fetal Medicine, Baltimore, Maryland *Present address: Professor & Head, Department of Ob/Gyn, The University of Iowa Hospitals & Clinics, Iowa City, IA 52242 Reprint requests: Dr. Witter, The Johns Hopkins University School of Medicine, Department of Gynecology and Obstetrics, Division of Maternal-Fetal Medicine, 600 North Wolfe Street, Baltimore, MD 21205 Copyright © 1990 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
Downloaded by: National University of Singapore. Copyrighted material.
A retrospective analysis utilizing historical data collected as part of our computerized data base was performed to assess the impact of marijuana use in pregnancy on pregnancy outcome. Records of 8350 patients were reviewed and 417 patients gave a history of only marijuana use for a prevalence of 5%. There was no association between marijuana use and prematurity or congenital anomalies. Marijuana use was strongly associated with the use of alcoholic beverages and smoking. Previously reported associations may represent the concomitant use of these other drugs.
MARIJUANA USE IN PREGNANCY/Witter, Niebyl Table 1. Outcome Versus Marijuana Use User
Nonuser
2991 ± 687* 29.4 ± 14.5* 594 ± 392* 24.0 17.8% 19.4% 84.4% 78.4%
3110 ± 755* 31.2 ± 14.8* 611 ± 457* 19.8 15.9% 17.1% 67.3% 37.5%
48.0% 5.3% 21.3% 1.2% 6.5% 5.52% 23.7% 7.7%
30.6% 0.9% 14.9% 0.9% 5.5% 4.59% 21.2% 9.8%
0.0192+ NS+ NS+ NS* NS* NS*
0.0032* 0.0032* 0.0032* 0.0128* NS* NS* NS* NS*
NS*
*Mean ± SD. t test. *Chi-square test. +
Table 2. Outcome Versus Marijuana Use for Whites Mean birthweight (gm) Smokers Alcohol consumption Social Heavy Anemia
User
Nonuser
P
3158 ± 673*
3247 ± 811*
NS+
80%
32.9%
0.0032*
69.2% 6.2% 3.1%
43%
0 0032*
0.2% 4.6%
NS*
*Mean ± SD. t test. *Chi-square test.
+
Table 3. Outcome Versus Marijuana Use for Nonwhites Mean birthweight (gm) Smokers Alcohol consumption Social Heavy Anemia
User 2960 ± 686*
Nonuser 3045 ± 717*
NS+
79.3%
37.2%
0.0032*
44.0% 5.1% 24.7%
24.6% 1.2% 19.9%
0.0032*
*Mean ± SD. f t test. *Chi-square test.
P
NS*
DISCUSSION
Prevalence of marijuana use in our population is 6% with a prevalence of marijuana use exclusive of other illicit drugs of 5%. This is somewhat below the estimate for women 18 to 25 years of age of 14%.* The estimate of use for persons 18 to 25 years of age may be high for our population or there may have been some underreporting among our patients. Although increased meconium staining has been reported with marijuana use,3 we found no difference in the incidence of meconium staining between marijuana users and nonusers. Furthermore, we found no increase in fetal distress in labor or perinatal mortality. Marijuana has been reported to decrease the length of gestation;4 however, we found no increase in prematurity in marijuana users when measured by percentage of infants with birthweights less than 2500 gm or by percentage of infants delivered at less than 37 weeks' gestation. An increased incidence of anemia appears to be associated with race rather than with marijuana use, for when stratified for race this association is no longer statistically significant. The highly significant difference between marijuana users and nonusers for cigarette smoking, alcohol use, and race may explain some of the associations seen in the past that were not seen in our study. Although lower birthweight has been reported with marijuana use and we saw such an effect in our nonstratified data, much of the difference is due to the racial difference between the users and nonusers. When stratified for race, the association was no longer statistically significant. We found no association between marijuana use and fetal anomalies either in general or in specific groups. Because of the strong association with alcohol use that we have seen, we believe that the previous report on the increased incidence of infants
Downloaded by: National University of Singapore. Copyrighted material.
Mean birth weight (gm) Weight gain (lbs) Duration of labor (min) Perinatal mortality (per 1000) Birthweight
