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Specific guide to this web site for:

 1.  Medical School
      in Statistics

 2.  Medical Students

 3.  Science media writers

 4.  High School & College
     Statistic Teachers


1. Harvard led MI study

2. JACC study 

   (J. of Amer. Coll.

3. NEJM cath study

4. Amer. J. of Cardio.
    review of literature


Oat bran study

Pregnancy & Alcohol

Are Geminis really
9. Columbia 'Miracle' Study  

Additional Topics:


Limitations of Meta-Analyses

Large Randomized Clinical Trials

Tale of Two Large

Advocate meta-analyses

Network meta-analyses





Roehm E.  Letter, Maternal alcohol consumption and birth weight. JAMA 1985:253:3551

To the Editor.--  In the October 12, 1984 issue of JAMA, Mills et al1 have published important prospectively gathered information on maternal alcohol consumption and its relation to birth weight.  Among their conclusions is that the adjusted odds ratio for small-for-dates infants is 1.1 for women drinking less than one drink per day and 1.62 for women drinking one to two drinks per day.

However, when the women are stratified by smoking status, it appears from their data as presented in Table 5 that the effects of drinking less than one drink per day or one to two drinks per day for a nonsmoking woman may not be important.  Specifically, the mean birth weight for nonsmokers is 3,468 grams (nondrinkers), 3,500 grams (less than one drink per day), and 3,452 grams (one to two drinks per day). Data are given for the odds ratio of a small-for-gestational-age infant being produced from different levels of alcohol consumption as a group but not specifically for nonsmokers.

Since 22,485 of the 31,604 pregnancies in this study were in nonsmokers, this consideration applies to a sizable portion of those studied and, hence, a group large enough for subgroup analysis. In addition, the authors have already analyzed crude birth weight for various levels of alcohol consumption when stratified by smoking status.  Hence, there is good rationale for the authors to supply further information on the small-for-gestational-age frequency for the different levels of alcohol consumption when stratified by smoking status.  This would help clarify further their findings for the large group of nonsmoking pregnant females.

A somewhat different interpretation of the data might then be made and is as follows.  For nonsmokers, drinking zero, less than one, or one to two drinks per day has negligible effect on the fetus size, and possibly on the development of small-for-gestational-age infants.  However, with these lower levels of alcohol consumption in smokers, there may be an effect on both crude birth weight and development of small-for-gestational-age infants.

This raises the possibility that there is a negative synergistic effect of smoking and low-level alcohol consumption on the infants of pregnant females.  Specifically, the decrement in crude mean birth weight for low levels of alcohol consumption is greater for smokers, suggesting that the combination of smoking and alcohol consumption is more than simply additive in its negative effect.

Although consumption of three drinks per day in nonsmoking pregnancies was associated with a decrease in the crude birth weight, consumption of lesser amounts of alcohol in the large group of nonsmoking females was without significant effect.  This contrasts with a possible detrimental effect of low level alcohol consumption in combination with smoking.

Eric Roehm, M.D.

Web site author's note:  This letter contains considerable speculation.

1.  Mills JL, Graubard BI, Harley EE, et al.  Maternal alcohol consumption and birth weight: How much drinking during pregnancy is safe? JAMA 1984:252:1875-1879