Blackwell Science, LtdOxford, UKCGACongenital Anomalies0914-3505The Japanese Teratology Society, 2004June 20044427986Original ArticleCongenital abnormalities and sulfonamidesA. E. Czeizel et al.

Congenital Anomalies 2004; 44, 79–86 79

ORIGINAL ARTICLE

Possible association between different congenital abnormalities and use of different sulfonamides during pregnancy

Andrew E. Czeizel1, Erzsébet Puhó1, Henrik T. Sørensen2, and Jørn Olsen2 1Foundation for the Community Control of Hereditary Diseases, Budapest, Hungary and 2Danish Epidemiology Science Center, Department of Epidemiology and Social Medicine, University of Aarhus, Department of Medicine V, Aarhus University Hospital, Aarhus, Denmark

ABSTRACT The objective of the study presented foot and sulfathiourea, both during the entire pregnancy here was to check the debated human teratogenic poten- (adjusted POR with 95% CI: 2.3, 1.2–4.3) and in the tial of sulfonamide drugs. Five different sulfonamides second and third months of gestation (3.9, 1.1–13.8). such as sulfamethazine, sulfathiourea, sulfamethoxypy- Thus, maternal treatment of sulfamethoxydiazine may ridazine, sulfamethoxydiazine and the combination of cause ventricular septal defect, while sulfathiourea may sulfamethazine-sulfathiourea-sulfamethoxypyridazine induce clubfoot; however, further studies are needed to were differentiated. verify or reject these associations. Cases with congenital abnormalities were compared with their matched controls without congenital abnor- Key Words: case-control analysis, clubfoot, human terato- malities in the population-based large data set of the genic potential, sulfamethoxydiazine, sulfathiourea, sulfona- Hungarian Case-Control Surveillance of Congenital mides, ventricular septal defect Abnormalities between 1980 and 1996. Of 38 151 newborn infants without any congenital INTRODUCTION abnormalities (control group), 163 (0.4%) had mothers who were treated with the sulfonamides studied during Sulfonamides are compounds with a radical -SO4NH. The pregnancy, while of 22 843 cases with congenital abnor- class of sulfonamides can be divided from clinical aspect malities, 140 (0.6%) had mothers who were treated with into three groups: (a) chemotherapeutics; (b) diuretics; and the sulfonamides studied during pregnancy. The analysis (c) antidiabetics. Here we are interested in the chemothera- of cases and matched controls indicated a higher rate of peutic group which includes many drugs used for the treat- cardiovascular malformation (adjusted prevalence odds ment of bacterial infections, among others, in pregnant ratios [POR] with 95% CI: 3.5, 1.9–6.4) and clubfoot women. Sulfonamides cross the placenta easily to the fetus (adjusted POR with 95% CI: 2.6, 1.1–6.2) in infants born during all stages of pregnancy (Barker 1938; Speert 1940), to mothers with sulfonamide treatment in the second and and an equilibrium with maternal blood is usually estab- third months of pregnancy. The detailed analysis of dif- lished after 2–3 h with a fetal level of 70–90% compared ferent sulfonamides showed a possible association with maternal level (Speert 1943; Sparr & Pritchard 1958). between cardiovascular malformations (adjusted POR In addition, sulfonamides inhibit the enzyme dihy- with 95%; CI: 6.5, 2.6–15.9), particularly ventricular dropteroate synthase in the folate metabolism and (Mandell septal defect (17.1, 1.3–141.1) and sulfamethoxydiazine & Sande 1990) therefore interfere with rapidly growing tis- during the second and third months of pregnancy. In sues. Thus, a possible teratogenic risk of sulfonamides has addition, a possible association was found between club- been suspected (Heckel 1941; Green 1963; Smithells 1966) which was supported by the results of animal experiments by mainly Japanese scientists (Nishimura & Tanimura 1976) but the findings of human studies in general did not confirm Correspondence: Andrew E. Czeizel MD, Törökvész lejtö32, 1026 Budap- est, Hungary. Email: [email protected] it (Heinonen et al. 1977; Rosa 1993). There are differences Received December 22, 2003; revised and accepted February 10, 2004. in the chemical structure, bioavailability, indication and

80 A. E. Czeizel et al. duration of treatment of chemotherapeutic sulfonamides; information on areas such as pregnancy complications, nevertheless, different anti-infective sulfonamides have been maternal diseases and drug intake during pregnancy accord- grouped together in previous teratological studies. The pop- ing to gestational months and the family history of CAs ulation-based large data set of the Hungarian Case-Control studied. To standardize the answers, mothers were asked to Surveillance of Congenital Abnormalities (HCCSCA) read the enclosed lists of drugs and diseases as a memory between 1980 and 1996 (Czeizel et al. 2001b) permits the aid before they replied. The time between the birth or preg- differentiation of anti-infective sulfonamides. Here the data nancy termination and return of questionnaire was 3.5 ± 1.2 of five drugs mainly used for the treatment of infectious and 5.2 ± 2.9 months in cases and controls, respectively. diseases in the respiratory system and urinary tract are Second, mothers were asked to send the antenatal care log- presented. book and other medical records concerning their diseases during pregnancy and their child’s CA after birth. Among MATERIALS AND METHODS respondents, the logbooks were available in 88.4 of cases and in 91.8% of controls. Third, regional nurses were asked The HCCSCA has two sources of subjects. Cases are to visit and question all non-respondent families of cases, selected from the Hungarian Congenital Abnormality Reg- thus, information was available on 96.3% (84.6% from reply, istry (HCAR) which is a national-based registry of cases 11.9% from visit) of cases without wrong or new unknown with congenital abnormality (CA) (Czeizel 1997). Notifica- addresses. The response rate for controls was 82.6%, but tion of CAs is mandatory for physicians, and most are regional nurses visited only 200 non-respondent families reported by obstetricians (in Hungary practically all deliver- (0.5%) because the committee on ethics considered this ies occur in inpatient obstetric clinics) and pediatricians follow-up to be disturbing to the parents of healthy children (working in the neonatal units of inpatient obstetric clinics (Czeizel et al. 2003). and various inpatient and outpatient pediatric clinics). The evaluation of sulfonamide exposure had seven differ- Autopsy was obligatory for all infant deaths and usual in ent aspects. (1) Source of information: (i) only data from the stillborn fetuses during the study period. Pathologists sent a antenatal care logbook and/or other medical records, mainly copy of the autopsy report to the HCAR if CAs were iden- discharge summary; (ii) only data from the questionnaire; tified in stillborn fetuses and infant deaths. The recorded and (iii) concordant data from both medical records and total (birth + fetal) prevalence of cases with CA diagnosed questionnaire. (2) Type of treatment (two groups): (i) sul- from the second trimester of pregnancy through the age of fonamide studied alone; and (ii)sulfonamide plus other 1 year was 35 per 1000 informative offspring (liveborn drugs were differentiated. (3) Route of administration: Five infants, stillborn fetuses and electively terminated mal- sulfonamides were used for oral treatment of pregnant formed fetuses) and about 90% of major CAs were reported women affected with infectious diseases of respiratory sys- to the HCAR during the 17 years of the study period (Czeizel tem and urinary tract in Hungary during the study period 1997). Minor variants or anomalies are excluded from the (Table 1). Sulfonamides were used in powder and ointment data set of the HCAR. The selection of cases with CAs from form as well; however, topical treatments in pregnant women the HCAR to the HCCSCA is based on three criteria. First, were excluded from this analysis. (4) Dose and (5) duration only cases are selected that were reported in the first three of treatment. Recommended treatment of oral sulfonamides months after birth or pregnancy termination. These cases studied are shown in Table 1. The half-life period of sulfona- comprised 77% of the HCAR (Czeizel 1997). Second, mides is short (Mandell & Sande 1990) so repeated daily among isolated CAs, three mild CAs (such as congenital treatment is necessary. (6) Gestational time was calculated dislocation of hip based on Ortolani click, congenital from the first day of the last menstrual period and three time inguinal hernia, and hemangiomas) are excluded. Third, CA intervals were considered: (i) First month of pregnancy, syndromes of Mendelian or chromosomal origin were not which is before the organogenesis. The first two weeks are selected for the data set of the HCCSCA. before conception, while the third and fourth weeks com- The other source of subjects without CA as controls were prise the pre-implantation and implantation period with ‘all- selected from the National Birth Registry of the Central or-nothing’ rule, i.e. CAs cannot be caused. (ii) The second Statistical Office. In general, two control newborn infants and third months of gestation as the critical period for most were matched to every case according to sex, birth date and major CAs. (iii) The fourth to ninth months of gestation. (7) district of parents’ residence. Potential confounding factors. Maternal age, birth order, Exposure data were collected from three different marital and employment status of mothers, acute and chronic approaches. First, a return postage paid explanatory letter maternal diseases and other drug uses were evaluated. and structured questionnaire, along with a list of drugs and The statistical analysis was based on the SAS version 8.02 diseases were mailed immediately after the selection of cases statistical software package (SAS Institute, Cary, North and controls to their parents. The questionnaire requested Carolina, USA). First, the prevalence of oral sulfonamide

Congenital abnormalities and sulfonamides 81 (95% CI) Adjusted POR** Hungarian Case- Hungarian

rnal disorders. POR (95% CI) = 38 151) Crude Controls n ( Cases = 22 843) 27 0.12 27 0.07 1.7 (0.9–2.8) 1.6 (0.9–2.7) n No. % No. % 142140 0.62 0.61 163 163 0.43 0.43 1.4 1.1–1.8 – 1.4 (1.1–1.8) – ( treatment (days) Mean duration of 500 500 2 1000–20002000 4 3 10 0.04 17 70 0.04 0.31 1.0 (0.5–2.1) 72 0.19 0.9 (0.4–2.0) 1.6 (1.2–2.3) 1.6 (1.1–2.2) 50050044 7 5 6 0.03 29 0.13 5 0.01 42 0.11 2.0 (0.6–6.6) 1.2 (0.7–1.9) 2.3 (0.7–7.6) 1.2 (0.7–1.9) ¥ ¥ ¥ ¥ ¥ ¥ ¥ ¥ Later 1 Later 1 Recommended daily treatment (mg or tbl) 167167 First day 3 Later 4 Dose of tablet (mg) + + Number of cases and controls who had mothers with treatment of five sulfonamides studied during pregnancy in the data set of sulfonamides studied during pregnancy Number of cases and controls who had mothers with treatment five Control Surveillance of Congenital Abnormalities (HCCSCA) between 1980 and 1996 of Congenital Control Surveillance *Synonym: sulfadimide; **prevalence odds ratios (POR) adjusted for maternal age and socio-economic status, birth order mate **prevalence sulfadimide; *Synonym: sulfathiourea (three)sulfathiourea 40 sulfamethoxypyridazine sulfamethoxypyridazine able 1 otal treatments Sulfonamides SulfathioureaSulfamethoxypyridazine 500 First day 2 500Persons 4 T Sulfamethoxydiazine Sulfamethazine 500T First day 2 Sulfamethazine* 500 3

82 A. E. Czeizel et al. treatments was compared between the study groups and not show obvious difference between treated cases and con- crude prevalence odds ratios (POR) with 95% confidence trols. The general high rate of infectious diseases in the interval (95% CI) were calculated. Second, the source of respiratory system and mainly urinary tract can be explained information was evaluated between case and control groups by the main indication of sulfonamides during pregnancy. using c2 test. Third, the prevalence of pregnancy complica- The occurrence of other frequently used drugs for acute tions and potential confounding factors were evaluated maternal infectious diseases showed similarities in the case between case and control groups using crude POR. Fourth, and control groups. the distribution of gestational months according to the start The starting frequency of sulfonamide use did not show of sulfonamide treatments was analyzed by c2 test. Finally, any difference according to gestational months. A maximum the prevalence of different sulfonamide treatments was of this treatment was seen during the fifth month in cases compared between cases and their matched controls. An and during the sixth month in controls. The use of sulfona- unconditional logistic regression model was used for the mide treatment was somewhat, but not significantly, less calculation of adjusted POR with 95% CI. Seven cases had frequent during the second and third months of gestation in no controls; they were replaced by extra controls chosen controls (22.0%) compared with the cases (27.7%). from rest of the 37 988 controls and were matched to each The analysis of cases and their matched controls in 12 relevant case. CA-groups (including three or more cases) (Table 3) showed that cases with cardiovascular CAs and clubfoot had more RESULTS mothers treated with sulfonamide both during the entire pregnancy and in the second to third months of gestation. There were 2 146 574 births in Hungary during the study The analysis of component CAs in the nine multiple CAs did period (i.e. between 1980 and 1996); hence, 38 151 controls not indicate any specific CA pattern. represented 1.8% of Hungarian births. Table 1 shows that Next, different sulfonamide uses were analyzed separately 163 controls (0.4%) had mothers who used sulfonamide in the group of cardiovascular CAs (Table 4) and clubfoot during pregnancy. The case group consisted of 22 843 mal- (Table 5). Adjusted POR were higher only for sulfamethox- formed offspring and 140 (0.6%) had mothers who were ydiazine in the second to third months of gestation in the treated by 142 sulfonamides studied during pregnancy. Thus, group with cardiovascular CAs (adjusted POR with 95% CI: two case pregnant women were treated by both sulfamethaz- 6.5, 2.6–15.9). Of 11 cases with cardiovascular CAs, eight ine (5th month) and sulfathiourea (6th month) and both were treated with sulfamethoxydiazine in the second and sulfathiourea (2nd month) and combination of three sulfona- third months of gestation. The distribution of these cardio- mides (8th month), respectively. In these two cases only the vascular CAs was as follows: ventricular septal defect, five; first treatment was considered when sulfonamides were eval- and complex, three (ventricular septal defect + atrial septal uated together. Of the five sulfonamides studied, only the defect + coarctation of aorta, ventricular septal defect + most commonly used, sulfathiourea, showed a higher prev- aortic stenosis, unspecified). Thus, all but one case had med- alence in the case group, However, the POR also exceeded ically recorded ventricular septal defect. The use of sul- 1.0 in the total case group. fathiourea was more frequent in both the second to third There was an obvious decline of sulfonamide use during months of gestation and during the entire pregnancy in the the study period: of 303 pregnant women with sulfonamide group of cases with clubfoot. There was no obvious differ- treatments, 250 (82.5%) had this treatment in the 1980s. ence between the adjusted POR between these two gesta- Sulfonamide alone was used only in 21 (12.9%) controls and tional periods. 13 (9.3%) cases, although pregnancy supplements (vitamins, iron and calcium derivatives) were excluded from the anal- DISCUSSION ysis. The use of sulfonamides alone and with other drugs therefore was combined in further analyzes. The proportion We estimate the teratogenic effect of five different sulfona- of medically recorded treatments was 41.7% in the control mides during pregnancy used for the treatment of acute 2 group, and 32.4% in the case group (c 1 = 9.91; P = 0.002). infectious diseases of urinary tract and respiratory system in The occurrence of pregnancy complications such as the mothers of cases with CA and their matched controls. excessive nausea and vomiting, threatened abortion and pre- The evaluation of data indicates some specific teratogenic term delivery, etc. did not show any significant differences risk of sulfonamides depending on the chemical structure of between the case and control groups. the drugs studied. A possible association was found between Potential confounding factors are shown in the total case ventricular septal defect and sulfamethoxydiazine treatment and control groups and within them subgroups treated with during the second and third months of pregnancy, as well as five sulfonamides studied in Table 2. Treated patients were an association between clubfoot and sulfathiourea use during somewhat younger, but marital and employment status did pregnancy.

Congenital abnormalities and sulfonamides 83

Table 2 Potential confounding factors

Cases Controls Total Treated Total Treated Potential confounding factors (n = 22 843) (n = 140) (n = 38 151) (n = 163) Maternal age, year (mean, SD) 25.5 5.3 24.6 5.0 25.5 4.9 25.5 4.6 Birth order (mean, SD) 1.9 1.1 1.7 1.0 1.7 0.9 1.7 0.8 Acute infectious diseases No. % No. % No. % No. % Influenza - common cold 4928 21.6 53 37.9 6986 18.3 46 28.2 Respiratory system 2056 9.0 28 20.0 3396 8.9 25 15.3 Digestive system 312 1.4 1 0.7 362 0.9 9 5.5 Urinary tract 1574 6.9 61 43.6 2285 6.0 46 28.2 Genital organs 1540 6.7 10 7.1 2699 7.1 20 12.3 Others 869 3.8 5 3.6 1214 3.2 6 3.7 Chronic maternal disorders Diabetes mellitus 56 0.3 0 0.0 52 0.1 0 0.0 Epilepsy 70 0.3 0 0.0 69 0.2 0 0.0 Others 3600 15.8 32 22.9 6577 17.2 38 23.3 Other drug uses (>300 in total) Aminophenazone 494 2.2 9 6.4 731 1.9 5 3.1 Ampicillin 1624 7.1 21 15.0 2598 6.8 18 11.0 Clotrimazole 1641 7.2 9 6.4 3077 8.1 14 8.6 Metronidazole 966 4.2 5 3.6 1415 3.7 12 7.4 Nitrofurantoin 774 3.4 25 17.9 1079 2.8 18 11.0 Noraminophenazone 1383 6.0 17 12.1 1912 5.0 12 7.4 Penamecillin 1597 7.0 27 19.3 2246 5.9 19 11.7 Sulfamethoxazole + trimethoprim 351 1.5 10 7.1 443 1.2 7 4.3

The strengths of the HCCSCA are (i) the population-based particularly in the case group. The explanation may be that (ii) large data set including 303 pregnant women with sul- sulfonamides were prescribed by other physicians indepen- fonamide treatment (iii) in a racially homogeneous European dently to antenatal care and/or recall bias in the control group population. In addition, (iv) the matching of cases and their because control mothers frequently forget short-term drug controls without CAs, (v) the knowledge of exposure time treatments during pregnancy after the birth of a healthy baby. of drugs studied and (vi) potential confounders, (vii) the (iii) Most women with sulfonamide use were treated with prospective and medically recorded data of sulfonamide other drugs as well, though their proportions were similar in treatments in a certain part of study groups. (viii) Finally, the study groups. (iv) Contrary to the large data set, the the diagnosis of reported CAs was checked and modified if number of cases with different sulfonamide uses during the it was necessary on the basis of recent medical records, thus second and third months of gestation in different CA-groups the validity of CA diagnosis is good (Czeizel et al. 2001b). was limited; therefore, confidence intervals were wide. However, this data set also has limitations. (i) The response The higher occurrence of ventricular septal defect in rate was nearly similar in controls (82.6%) and cases children born to mothers who had sulfamethoxydiazine (84.4%); however, there was an active follow-up for all non- treatments during pregnancy needs to be discussed for the respondents in the case group but only 200 in the control identification of possible biases. As we have argued previ- group. These asymmetries may cause a selection bias, but ously, selection bias does not seem to be important. How- the frequency of commonly used drugs including sulfona- ever, since the birth of an infant with a CA is a serious and mides in the non-respondent controls did not differ signifi- traumatic event for most mothers, the mothers try to find a cantly from the rate of control pregnant women who causal explanation such as drug use during pregnancy, which responded (Czeizel et al. 2003). (ii) The data were fre- is not the case after the birth of a healthy baby. Recall bias quently based only on maternal self-reported information, can mimic an increased risk (Rockenbauer et al. 2001).

84 A. E. Czeizel et al.

Table 3 Prevalence of sulfonamides treatment in controls and cases with different congenital abnormalities groups

Second and third months Entire pregnancy Study groups No. % POR* 95% CI No. % POR* 95% CI Total Controls 38 0.1 Referent 163 0.4 Referent 38 151 Cases with isolated CAs Neural-tube defects 2 0.2 1.3 0.3–5.4 10 0.8 1.5 0.8–2.9 1 202 Cleft lip ± palate 0 0.0 – – 4 0.3 0.6 0.2–1.6 1 374 Cleft palate 1 0.2 1.6 0.2–11.4 5 0.8 1.8 0.7–4.5 601 Hypospadias 6 0.2 2.1 0.9–5.1 16 0.5 1.3 0.7–2.1 3 038 Undescended testis 2 0.1 1.2 0.3–5.0 11 0.5 1.4 0.8–2.7 2 051 Ear CAs 1 0.3 3.0 0.4–22.1 3 0.9 2.0 0.6–6.3 354 Cardiovascular CAs 14 0.3 3.5 1.9–6.4 34 0.8 1.9 1.3–2.8 4 479 Clubfoot 6 0.3 2.6 1.1–6.2 18 0.7 1.7 1.1–2.8 2 424 Limb deficiencies 1 0.2 1.7 0.2–12.4 4 0.7 1.6 0.6–4.2 548 Poly/syndactyly 2 0.1 1.3 0.3–5.5 10 0.6 1.5 0.8–2.8 1 744 Other isolated CAs 4 0.1 1.1 0.4–3.1 16 0.4 1.0 0.6–1.7 3 679 Cases with multiple CAs 2 0.2 1.4 0.3–5.9 9 0.7 1.4 0.7–2.8 1 349 Total 41 0.2 1.8 1.2–2.8 140 0.6 1.4 1.1–1.8 22 843 *Prevalence odds ratios (POR) adjusted for maternal age and socio-economic status, birth order and maternal disorders. CA, congenital abnormality.

Table 4 Five different sulfonamides used separately in cases with congenital cardiovascular abnormalities and adjusted prevalence odds ratios with 95% CI for confounders†

Cases with cardiovascular Controls Second and third CAs (n = 4479) (n = 38 151) Entire pregnancy months Sulfonamides No % No % POR** 95% CI POR** 95% CI Sulfamethazine 1 (0) 0.02 17 (5) 0.04 0.5 0.1–3.6 – – Sulfathiourea 13 (3) 0.29 72 (12) 0.19 1.6 0.9–2.9 2.2 0.6–7.9 Sulfamethoxypyridazine 2 (1) 0.04 5 (2) 0.01 4.3 0.8–22.5 4.8 0.4–53.5 Sulfamethoxydiazine 11 (8) 0.25 42 (12) 0.11 2.5 1.3–4.8 6.5 2.6–15.9 Combination of three* 7 (2) 0.16 27 (7) 0.07 2.3 1.0–5.4 2.8 0.6–13.5 †Data of cases and controls during the second to third months of gestation are shown in brackets. *See Table 1; **prevalence odds ratios (POR) adjusted for maternal age and socioeconomic status, birth order and maternal disorders.

Accordingly, a higher proportion of sulfonamide treatment second and third gestational months are considered as the during pregnancy was reported by case mothers. Neverthe- critical period for ventricular septal defect. There was a less, it is possible to limit recall bias by different approaches. much higher POR for sulfamethoxydiazine treatments dur- First, in general, teratogens cause only one or few types of ing the second and third months of pregnancy. The third CAs due to noxa specificity. The detailed analysis of CAs aspect is the use of another, more valid source of exposure indicated only the higher occurrence of cardiovascular CAs data. Medically recorded data may serve as a golden stan- and within them ventricular septal defect after maternal dard, however, of eight cases with ventricular septal defect sulfamethoxydiazine treatment during pregnancy. Second, connected with the second and third months of gestation, treatment by sulfonamides was evaluated in the specific peri- only three had medically recorded drug use. ods of gestation. The ventricular septum closes in the 6th Another possible association was found between sul- postconceptional week (i.e. 8th gestational week), thus, the fathiourea and clubfoot. However, the group of clubfoot

Congenital abnormalities and sulfonamides 85

Table 5 Use of five different sulfonamides separately in cases with clubfoot and adjusted POR with 95% CI for confounders†

Cases with clubfoot Controls Second and third (n = 2424) (n = 38 151) Entire pregnancy months Sulfonamides No. % No. % POR** 95% CI POR** 95% CI Sulfamethazine 1 (0) 0.04 17 (5) 0.04 1.0 0.1 -7.2 – – Sulfathiourea 11 (3) 0.45 72 (12) 0.19 2.3 1.2–4.3 3.9 1.1–13.8 Sulfamethoxypyridazine 0 (0) 0.00 5 (2) 0.01 – – – – Sulfamethoxydiazine 4 (2) 0.17 42 (12) 0.11 1.6 0.6–4.5 3.0 0.7–13.5 Combination of three* 2 (1) 0.08 27 (7) 0.07 1.1 0.3–4.7 2.2 0.3–17.7 †Data of cases and controls during the second and third months of gestation are shown in brackets. *See Table 1; **prevalence odds ratios (POR) adjusted for maternal age and socio-economic status, birth order and maternal disorders. includes heterogeneous entities including congenital talipes fathiourea was not studied, while sulfamethoxydiazine was equinovarus such as a true CA with a critical period in the considered as teratogenic mainly due to a higher rate of cleft early pregnancy and deformations due to intrauterine palate (Kato & Kitagawa 1973a,b). mechanical factors in the third trimester of gestation. Thus, our findings are not consistent with the previous Some case reports have indicated the possible association human and animal investigations, thus we cannot exclude of sulfonamide treatment during pregnancy and oesophageal that these associations are due to confounding factors such atresia (Ingalls & Prindle 1949) or congenital cataract (Harly as underlying diseases or multiple testing. However, et al. 1964). Two epidemiological studies also indicated the maternal disorders were considered as confounders and possible human teratogenic risk. In a retrospective study of different analysis of our data set indicated two possible 1369 patients, significantly more mothers of 458 infants with associations between different sulfonamides and CAs. We CA took sulfonamides than mothers in the control group generate a hypothesis for the possible association between (Nelson & Forfar 1971), while a higher use of sulfonamides ventricular septal defect and sulfamethoxydiazine. In gen- during the first and second trimesters of pregnancy was found eral, sulfonamides interfere with folate metabolism due to in mothers who delivered babies with syndromic oral cleft the inhibition of enzyme dihydropteroate synthase and this (i.e. the combination of cleft lip and/or cleft palate with other vitamin B plays a key role in DNA and RNA synthesis CAs) than in the newborn infants of matched control mothers through several enzymatic pathways. Antifolate metabo- (Saxen 1975). However, some other studies have failed to lites produced cardiovascular CAs in rats (Baird et al. confirm the human teratogenic effect of sulfonamides; only 1954; Monie & Nelson 1963); however, a reduced occur- two large studies are mentioned here. The Collaborative rence of cardiovascular CAs, in particular conotruncal Perinatal Project monitored 50 282 mother–child pairs. The defects and ventricular septal defect, was found after peri- findings did not suggest a relationship to major groups of conceptional folic acid-containing multivitamin supple- CAs and sulfonamide uses in the first trimester of gestation mentation in some studies (Czeizel 1993, 1996; Shaw in 1455 pregnant women (Heinonen et al. 1977). Among et al. 1994; Botto et al. 1996, 2000), except in one cardiovascular CAs, only patient ductus arteriosus (eight study (Werler et al. 1998). It is possible that sulfamethox- cases) was mentioned as having a possible association with ydiazine has a stronger inhibitive effect for dihy- sulfonamide treatment. In a surveillance study of Michigan dropteroate synthase than other sulfonamides. Recently, Medicaid recipients involving 229 101 completed pregnan- sulfonamides have been used, mainly in combination with cies conducted between 1985 and 1992, 131 fetuses had been trimethoprim, and human teratogenic effect of cotrimox- exposed to oral sulfonamides and eight (6.1%) major CAs azole has been shown (Hernandez-Diaz et al. 2000; Czei- were observed (six expected), including two cardiovascular zel et al. 2001a). CAs (one expected) (Rosa 1993). A recent study of drug use In conclusion, the findings of the study presented here during early pregnancy in mothers who later delivered babies suggest that different sulfonamides may have different ter- with cardiovascular CAs did not show the teratogenic poten- atogenic effects because a possible association was found tial of sulfonamides (Källen & Olansson 2003). However, between sulfamethoxydiazine treatment during the second different sulfonamides were not separated in these studies and third months of pregnancy as well as ventricular septal and appropriate control groups were not available. defect. In addition, a weaker association was seen between The teratogenic and fetotoxic effect of some sulfonamides sulfathiourea and clubfoot. Further case–control studies are were investigated in some species of animals; however, sul- needed to verify or reject these associations.

86 A. E. Czeizel et al.

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