The Problem of Confounding in Studies of the Effect of Maternal Drug Use on Pregnancy Outcome

Table 4

Importance of maternal education level in Sweden for the use and/or reporting of various categories of drugs in early pregnancy [2]. Nine years of education is compulsory. Most women have 12 years of education which is used as the reference group. Adjusted for year of delivery, maternal age, parity, smoking, and BMI.

	Low education, <12 years of education		High education, ≥14 years of education
Drug group	OR	95% CI	OR	95% CI
Drugs for ulcer and gastrointestinal reflux	1.20	1.08–1.53	0.81	0.75–0.88
Multivitamins and minerals	0.92	0.66–1.29	1.11	0.89–1.38
Anticoagulants	1.04	0.81–1.33	0.96	0.81–1.14
Haemostatics	1.42	1.01–2.00	1.08	0.85–1.38
Antihypertensives	0.85	0.71–1.00	0.82	0.73–0.92
Oral contraceptives in early pregnancy	0.88	0.87–1.02	0.72	0.62–0.83
Systemic corticosteroids	0.86	0.72–1.01	1.03	0.92–1.15
Thyroxine substitution	0.91	0.82–1.01	0.91	0.84–0.97
Antibiotics	0.90	0.85–0.95	1.07	1.03–1.11
Antivirus drugs	0.84	0.85–1.37	1.35	1.08–1.69
Vaccines	0.92	0.62–1.35	1.53	1.26–1.86
NSAID	0.90	0.83–0.97	0.87	0.82–0.92
Analgesics	1.04	1.01–1.08	0.93	0.91–0.96
Drugs for migraine	0.92	0.76–1.11	0.85	0.75–0.97
Anticonvulsants	1.49	1.26–1.76	0.71	0.61–0.82
Antipsychotics	1.52	1.17–1.99	0.97	0.93–1.28
Sedatives/hypnotics	1.75	1.56–1.96	0.86	0.76–0.98
Antidepressants	1.48	1.35–1.61	0.78	0.72–0.85
Drugs used for malaria prophylaxis	0.87	0.55–1.37	2.08	1.08–2.57
Antiasthmatics	0.96	0.91–1.02	0.90	0.97–0.99
Antihistamines used for allergy	0.77	0.70–0.82	1.11	1.05–1.17
Ophthalmics	0.63	0.47–0.86	1.35	1.17–1.56