Obstetrics and Gynecology International Table 6: Importance of the mother’s country of birth on the occurrence of relatively severe malformations in the infant. Odds ratios adjusted for year of birth, maternal age, parity, smoking, and BMI. Reference is infants born by mothers born in Sweden. Data for years 2000–2008. Number of infants 727166 16612 % of all infants 81.9 1.9 % malformed infants 2.7 2.5 10 Geographic area Sweden Other Nordic countries Western Europe, Northern America, Australia, New Zealand Eastern Europe and former Soviet Union Sub-Saharan Africa North Africa and Middle East Asia South and Middle America All non-Nordic countries Drug group Drugs for stomach ulcer and reﬂux Drugs for inﬂammatory bowel disease Insulin Multivitamins Folic acid Oral contraceptives during pregnancy Gonadotropins Systemic corticosteroids Thyroid drugs Antibiotics NSAIDs Opioids Minor analgesics Anticonvulsants Antipsychotics Sedatives, hypnotics Drugs for rhinitis Antiasthmatics Antihistamines 10504 25855 15488 54186 27405 10373 143811 1.2 2.9 1.7 6.1 3.1 1.2 16.2 Number of users 316 41 49 559 519 160 22 65 317 321 300 261 835 110 283 1202 146 533 1097 Table 7: Concomitant drug use in early pregnancy among 11,181 women who used antidepressants [2]. Odds ratios (ORs) with 95% conﬁdence intervals (95% CI) for use of speciﬁc group categories in women using antidepressants compared with women who did not. Adjustment for year of birth, maternal age, parity, smoking in early pregnancy, and BMI. teratogenic eﬀect, but the combination of the two drugs had. This observation, based on rather few cases, has not yet been conﬁrmed in an independent material. 3.5. Confounding by Infant Characteristics 3.5.1. Infant Sex. Some malformations show a deviating sex ratio, sometimes extreme (like hypospadias which in practice only exists in males). Is there then a reason to adjust for infant sex in the analysis of drug eﬀects? If the use of a drug is aﬀected by infant sex, this would lead to confounding and adjustment for sex should be made. Thus, for instance, subluxation of the hip is more common in girls than in boys (sex ratio 0.37 instead of 1.06 among all neonates) and women who carry a girl fetus are slightly more likely to experience nausea and vomiting in pregnancy (NVP) and therefore also to use drugs for that condition (for instance, antihistamines with an antiemetic eﬀect). In a study of the use of meclozine, the infant sex ratio was 0.92 instead of 1.06 [26]. If one wants to study the possible relationship between the use of meclozine (or NVP) and occurrence of subluxation of the hip in the newborn, an adjustment for infant sex is therefore called for. Actually, this changes the odds ratio very little: from 0.95 (95% CI 0.82–1.08) to 0.91 (95% CI 0.71–1.05). 2.6 2.5 2.7 2.9 2.2 2.4 2.6 OR 2.92 1.27 1.13 0.78 0.82 3.52 0.85 1.55 1.89 0.92 1.21 3.48 0.83 3.17 7.13 25.9 0.92 1.40 1.79 OR 1.00 0.87 0.96 0.89 0.97 1.04 0.82 0.84 0.94 95% CI Reference 0.79–0.96 0.85–1.08 0.83–0.97 0.88–1.08 0.98–1.09 0.75–0.89 0.74–0.96 0.91–0.98 95% CI 2.61–3.26 0.93–1.73 0.85–1.50 0.72–0.85 0.75–0.90 3.02–4.11 0.56–1.28 1.21–1.98 1.69–2.11 0.82–1.03 1.08–1.36 3.09–3.93 0.77–0.89 2.63–3.82 6.39–7.97 24.6–27.3 0.78–1.09 1.28–1.53 1.68–1.90