8 Obstetrics and Gynecology International 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. Drug group Drugs for ulcer and gastrointestinal reﬂux Multivitamins and minerals Anticoagulants Haemostatics Antihypertensives Oral contraceptives in early pregnancy Systemic corticosteroids Thyroxine substitution Antibiotics Antivirus drugs Vaccines NSAID Analgesics Drugs for migraine Anticonvulsants Antipsychotics Sedatives/hypnotics Antidepressants Drugs used for malaria prophylaxis Antiasthmatics Antihistamines used for allergy Ophthalmics Low education, <12 years of education OR 95% CI 1.20 1.08–1.53 0.92 0.66–1.29 1.04 0.81–1.33 1.42 1.01–2.00 0.85 0.71–1.00 0.88 0.87–1.02 0.86 0.72–1.01 0.91 0.82–1.01 0.90 0.85–0.95 0.84 0.85–1.37 0.92 0.62–1.35 0.90 0.83–0.97 1.04 1.01–1.08 0.92 0.76–1.11 1.49 1.26–1.76 1.52 1.17–1.99 1.75 1.56–1.96 1.48 1.35–1.61 0.87 0.55–1.37 0.96 0.91–1.02 0.77 0.70–0.82 0.63 0.47–0.86 High education, ≥14 years of education OR 95% CI 0.81 0.75–0.88 1.11 0.89–1.38 0.96 0.81–1.14 1.08 0.85–1.38 0.82 0.73–0.92 0.72 0.62–0.83 1.03 0.92–1.15 0.91 0.84–0.97 1.07 1.03–1.11 1.35 1.08–1.69 1.53 1.26–1.86 0.87 0.82–0.92 0.93 0.91–0.96 0.85 0.75–0.97 0.71 0.61–0.82 0.97 0.93–1.28 0.86 0.76–0.98 0.78 0.72–0.85 2.08 1.08–2.57 0.90 0.97–0.99 1.11 1.05–1.17 1.35 1.17–1.56 Table 5: Importance of maternal education or non-cohabitation for occurrence and diagnosis of congenital malformations in Sweden. Odds ratios (ORs) with 95% conﬁdence intervals (95% CI) for various malformation groups at diﬀerent maternal education levels. For educational level, the reference is 12 years of education, for non-cohabitation, the reference is cohabitation. Adjustment for year of birth, maternal age, parity, smoking, and BMI. Malformation group Relatively severe malformations Chromosome anomalies Neural tube defects Orofacial clefts Cardiovascular defects Severe kidney malformation Hypospadias Pes equinovarus (Sub)luxation of hip Craniostenosis <12 years of education OR 95% CI 1.05 1.00–1.10 1.04 0.86–1.26 0.75 0.40–1.16 0.99 0.81–1.21 1.02 0.94–1.61 1.07 0.78–1.46 1.24 1.06–1.45 0.86 0.69–1.07 0.90 0.80–1.01 0.75 0.53–1.07 ≥14 years of education OR 95% CI 0.97 0.93–1.00 0.96 0.84–1.10 0.97 0.73–1.30 0.89 0.77–1.03 0.97 0.87–1.08 0.98 0.86–1.13 0.78 0.62–0.98 0.94 0.69–1.26 0.98 0.64–1.49 1.01 0.68–1.51 Non-cohabiting in early pregnancy OR 95% CI 0.99 0.95–1.06 0.99 0.75–1.29 1.49 0.89–2.48 0.95 0.71–1.26 1.08 0.97–1.22 0.99 0.62–1.57 0.85 0.66–1.10 1.00 0.75–1.33 0.76 0.63–0.91 0.94 0.58–1.54 slightly increased or decreased, but for some drug groups and notably for CNS active drugs, more marked diﬀerences are seen. To what extent these diﬀerences are due to diﬀerent prevalence of underlying disease or to diﬀerent drug use at similar underlying disease patterns is diﬃcult to disentangle. The signiﬁcance of socioeconomic factors as confounders varies between populations, mainly according to the impact on malformation risk. Table 5 indicates that, in Sweden, maternal education as a proxy for socioeconomic level has little impact on malformation rate if adjustment is made for age, parity, smoking, and BMI. For speciﬁc malformations and notably for hypospadias, an association seems to exist with a moderately increased risk at short education and a possibly lower risk at high education. This could confound