Congenital malformations among offspring exposed in utero to progestins, Olmsted County, Minnesota, 1936–1974*

Vol. 43, No.4, April 1985 Printed in U.SA.

FERTILITY AND STERILITY Copyright © 1985 The American Fertility Society

Congenital malformations among offspring exposed in utero to progestins, Olmsted County, Minnesota, 1936-1974*

LaurelI~e J. Resseguie, Ph.D.t:j: John F. Hick, M.D.§ Judith A. Bruen, RN.t Kenneth L. Noller, M.D.II William M. O'Fallon, Ph.D. t Leonard T. Kurland, M.D., Dr.P.H.t Mayo Clinic and Mayo Foundation, Rochester, Minnesota

Comparison of a cohort of 988 offspring exposed in utero to exogenous progestins with a matched cohort of unexposed offspring did not result in detection of an association of congenital anomalies with exposure. The conclusions are based primarily on outcomes of pregnancy with exposure to progesterone and 17o.-hydroxyprogesterone caproate, and may not apply to androgenic progestins. Offspring exposed to combinations of progestins and estrogens were excluded from this study and may have a different distribution of anomalies. Fertil Steril43:514, 1985

There are many articles in the literature that suggest that progestins given exogenously to pregnant women have detrimental effects on fetal development. Most organ systems have been cited, but attention has been directed especially to the masculinization of female genitals, 1 hypospadias,2 cardiovascular malformations,3 VACTERL (a multiple malformation syndrome affecting skeletal, digestive, respiratory, and renal systems),4 and an increased propensity for academic achievement. 5

Received October 26, 1984; revised and accepted December 19, 1984. *Supported in part by the National Institutes of Health, Public Health Service, grant AM 30582. tDepartment of Medical Statistics and Epidemiology. :j:Reprint requests: Laurence J. Resseguie, Ph.D., Department of Medical Statistics and Epidemiology, Mayo Clinic, Rochester, Minnesota 55905. §Department of Pediatrics. IIDepartment of Obstetrics and Gynecology.

514

Resseguie et al. Malformations after progestin exposure

Other investigators 6 have reported no disturbances of fetal development associated with progestin exposure. Any attempt to reconcile these conflicting reports is complicated because of the many different progestational drugs that have been used. Some of the agents are known to have androgenic activity; others are metabolized to steroids with different hormonal activities. Additionally, outcomes in fetuses exposed to combinations of estrogens and progestins have often been grouped with those in fetuses exposed to progestins alone. It is quite possible that some of the fetal effects that have been attributed to progestins are the consequence of other hormonal activity or the combination of hormones. The present study was designed to determine whether there is an increased risk of congenital anomalies among fetuses exposed to progestins in the absence of other sex hormone exposures. This question remains pertinent to contemporary medical practice because treatment of pregnant women with progestins continues. The medFertility and Sterility

ical literature has recently suggested the use of 17a-hydroxyprogesterone caproate for the prevention of premature labor 7 ;progesterone was suggested for the prevention of preeclampsia among pregnant women presenting with headache, vomiting, depression, or lethargy in 1981 5 ; and progesterone continues to be suggested for treatment for habitual abortion. 8 MATERIALS AND METHODS

The medical records of 24,000 women who received their prenatal care at the Mayo Clinic were manually reviewed to identify those children who were exposed to sex hormones before birth. All singleton live and stillborn children who were delivered by Mayo Clinic physicians between January 1, 1936 and December 31,1974, to mothers who were residents of Olmsted County, Minnesota, were eligible for inclusion in this study. All eligible children who were found to have been exposed in utero to any exogenous progestin but who were not exposed to any other sex hormone or gonadotropin comprise the exposed cohort (referred to as index subjects). Control subjects were matched to each index subject by sex of child, age of mother, and number of previous liveborn children. The two potential control subjects whose dates of birth were closest to that of the exposed child and whose records did not show exposure to any sex hormone or gonadotropin before birth were chosen. The data from the medical records of the mothers were abstracted by a single investigator (L. J. R.). All medical records in Rochester, Minnesota, of the children in both cohorts were manually searched for diagnoses of anomalies and malignancies by a single investigator (J. A. B.) who did not know the exposure status of the child. Questionable diagnoses were resolved by J. F. H., who also did not know the exposure status of the child. The diagnosis of many of the anomalies can be found exclusively in the original medical record. No registry could be used to retrieve all diagnosed anomalies. Fitting of log linear models was performed by means of the computer program ECT A (Everyman's Contingency Table Analysis).9 The likelihood ratio statistic, G2

=

2~ 1

Xi

log

_X;_

m;

,

was

used as the summary statistic to measure goodness of fit for each model. If two models differ only by the presence or absence of a parameter exVol. 43, No.4, April 1985

pressing the association between progestin exposure and offspring malformation and fit the data satisfactorily, the difference in G2 between the two models provides a test of the hypothesis of no association. If exposure and malformation are independent, the difference should be distributed as chi-squared with one degree of freedom. 10 This method of analysis ignores an awkward reality of the study of congenital malformations. Malformations, including major cardiovascular anomalies, are often not diagnosed until months or years after birth. The frequency of detected anomalies, therefore, increases with duration of follow-up. For this reason, the unexposed and progestin-exposed cohorts were compared, using statistical methods developed for the study of what are frequently referred to as "failure time" (e.g., time until detection of the malformation) data, which allow for differing lengths of follow-up and for the fact that in many subjects no "failure" occurs during the follow-up period. Specifically, the proportional hazards model of Cox with the exposed/unexposed triplets as strata as outlined by Kalbfleisch and Prentice,l1 was used to compare the two cohorts while adjusting for the influence of potential covariates. Offspring were considered lost to follow-up after the last entry in the records of the medical care facilities of Olmsted County. These analyses were accomplished by using the BMDPprogram P2L for regression with incomplete survival data. 12 RESULTS

The majority of the subjects were exposed to 17a-hydroxyprogesterone caproate (Delalutin, E. R. Squibb & Sons, Princeton, NJ). Progesterone is the only other progestin which is strongly represented. Only 141 subjects were exposed to other progestins (Table 1). Exposure began durTable 1. Frequency of Exposure to Specific Progestins in Progestin-Exposed Birth Cohort, Olmsted County, Minnesota, 1936-1974 Agent

17a-hydroxyprogesterone caproate (Delalutin) Progesterone Medroxyprogesterone Ethisterone Algesterone acetophenide Norethindrone Dydrogesterone

No. of offspring exposed a

649 244 60 45 24 11 1

aSome offspring were exposed to more than one progestin.

Resseguie et aI. Malformations after progestin exposure

515

Table 2. Day of Gestation of First Exposure to Progestins, Olmsted County, Minnesota, 1936-1974 Starting day"

Earliest 25th centile Median 75th centile Latest

Any progestin

0 46 60 84 266

17a-hydroxyprogesterone Progesterone caproate

4 47 60 82 249

0 43 59.5 93.5 266

"The first day of exposure cannot be determined for 37 of the 988 exposed offspring.

ing the first trimester for 742 of the 988 subjects. The starting date could not be determined for 37 subjects. Exposure began within the first 10 weeks of gestation for 594 offspring. Additional details of the distribution of starting day of exposure are presented in Table 2. Estimation of the total dose of progestin was possible for 501 of the subjects, who were exposed to 17o:-hydroxyprogesterone caproate only (Table 3). Table 4 demonstrates that the exposed and unexposed cohorts are very similar with respect to those maternal variables for which they were matched. Several substantial differences between the cohorts were noted for specific unmatched variables. The mean follow-up for offspring that survived the perinatal period was 11.5 years. The mean follow-up for progestin-exposed offspring was 4 months greater than for unexposed offspring. No tendency for an excess of cardiovascular, central nervous system or limb reduction anomalies, or hypospadias was observed in the exposed cohort (Table 5). No offspring in the study met the criteria for the VACTERL syndrome. Because specific anomalies are rare, comparisons of grouped anomalies were made. All major anomalies were combined, and the two cohorts were compared. Also, all anomalies were combined, and the two cohorts were compared. These comparisons were explored through fitting log linear models to the observations which were cross-classified by five dichotomous variables: malformation of offspring, progestin exposure, occurrence of fetal or neonatal death or malformation in a previous pregnancy ofthe mother, record of a congenital anomaly of the mother, and occurrence of bleeding during gestation. These comparisons were also explored by use of the proportional hazards model of Cox, 11 with the matched triplets of exposed and unexposed offspring as strata. Various combinations of covari516

Resseguie et al. Malformations after progestin exposure

ates were introduced into the models selected from among occurrence of bleeding during gestation, death or malformation in a previous pregnancy of the mother, record of a congenital anomaly of the mother, record of the mother's examination or treatment for infertility, and age of the mother. Age of the mother was one of the variables used for matching triplets, but it was not possible to achieve perfect matching. No test provided justification for rejection ofthe hypothesis that progestin exposure and the occurrence of anomalies are independent events. This is true for major anomalies as well as for all anomalies and is also true if only first-trimester exposure is considered. Over 60% of all the progestin cohort were exposed only to 17o:-hydroxyprogesterone caproate (Delalutin). Outcomes for these offspring are found in Table 6. All observations in this table are included within Table 5. "Abnormal testis" (primarily undescended) was observed more frequently among the exposed, but this did not constitute a statistically significant difference from the unexposed. DISCUSSION

This study provides no support for the concept that progestins in general, and Delalutin specifically, cause anomalies when given exogenously to pregnant women. The higher frequencies of bleeding during pregnancy and prior fetal and neonatal deaths in the exposed cohort (Table 4) would lead to the expectation of an excess of malformations even in the absence of any teratogenic effect of progestins. Because all children who had been exposed to estrogen, other sex hormones, or gonadotropins were excluded from the study group, these results have no bearing on the possible teratogenic effects of the combination of progestins with other hormones. Because only 11 of the offspring in this study were exposed to progestins with known androgenic properties, the Table 3. Distribution of Total Dose of 17o.-Hydroxyprogesterone Caproate Among 501 Offspring Not Exposed to Other Progestins, Olmsted County, Minnesota, 1936-1974 Milligrams

Minimum 25th centile Median 75th centile Maximum

125 500 1625 3000 11,250

Fertility and Sterility

Table 4. Maternal Variables in Progestin-Exposed and Unexposed Cohort, Olmsted County, Minnesota, 1936-1974 Variables Matched variable Age of mother Prior live births Unmatched variable Gravida Prior miscarriages Prior fetal and neonatal deaths

Bleeding during gestation Record of congenital anomaly of mother

Exposed

Unexposed

Mean

SDa

Median

Mean

SD

Median

27.6 1.3

5.0 1.3

27 1

27.3 1.3

4.7 1.3

27 1

3.2 0.8 0.9

1.8 1.0 1.1

3 0 1

2.5 0.2 0.3

1.5 0.6 0.6

2 0 0

No.

%

No.

%

578 281

59 28

365 484

18 24

aSD, standard deviation.

study cannot provide evidence concerning the hazards of those products. The apparent excess of premature deliveries and neonatal deaths among the exposed probably reflects the overrepresentation of high-risk pregnancies among the exposed cohort, usually the reason for prescription of the progestin. The proportion of mothers of exposed offspring who experienced bleeding in pregnancy was three times that among mothers of the unexposed cohort. Fetal and neonatal deaths in prior pregnancies were three times as frequent among the exposed cohort as among the unexposed cohort. The data which form the basis of most allegations that progestins cause birth defects differ fundamentally from this study by including estrogen exposure or by being dominated by progestins with known androgenic activity. This difference may be responsible for the discrepancy in observations. I -4 , 14-16 The search for associations between progestins and anomalies has generated other negative reports,5, 6,17-19 and some positive reports may be the result of sampling variation. Published reports of laboratory experiments demonstrate that progestins can be embryotoxic or teratogenic if given in sufficient dose. It is generally not possible to relate these reports to the present study because the laboratory test doses are so far above the human therapeutic range and the specific progestins tested are, for the most part, not found in this clinical series. In addition, species differences in response to specific hormones are commonplace. For example, two progestins caused masculinization of female rat fetuses, whereas progesterone did not. 20 Chlormadinone acetate was found to be teratogenic when Vol. 43, No.4, April 1985

administered to mice and rabbits, but only at doses well above the therapeutic range. 21 A recent report of teratogenicity and embryotoxicity of lynestrenol in rabbits exemplifies the problem of relating laboratory experiments to clinical data. Table 5. Outcomes Noted in Progestin-Exposed and Unexposed Cohort, Olmsted County, Minnesota, 1936-1974 Exposed Outcome

Unexposed

(n = 988)

No.

11 Stillbirth 89 Birth weight < 2500 gm Neonatal death 26 Any major anomalya 54 Any anomaly Including hydrocele 280 Excluding hydrocele 254 Genitourinary anomaly 88 Including hydrocele Excluding hydrocele 36 Anomaly of female 12 genitalia Anomaly of male 16 genitalia 5 Hypospadias 9 Abnormal testis Central nervous sys25 tem anomaly (including spina bifida occulta and sinus tract abnormalities) 4 Major central nervous system anomaly Major cardiovascular 9 anomaly Inguinal hernia 52 1 Limb reduction defect Malignancy 4

%

(n = 1976)

No.

%

1.1 9.0

20 92

1.0 4.7

2.6 5.5

20 88

1.0 4.5

28.3 25.7

478 431

24.2 21.8

8.9 3.6 2.5

151 53 18

7.6 2.7 1.9

3.1

25

2.4

1.0 1.8 2.5

15 12 46

1.5 1.2 2.3

0.4

9

0.5

0.9

18

0.9

5.3 0.1 0.4

83 4 6

4.2 0.2 0.3

a Anomalies were classified as major or minor after the list of anomalies reported in appendix 2 of Heinonen et al. 13

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Malformations after progestin exposure

517

Table 6. Outcomes Noted in 17a.-Hydroxyprogesterone Caproate (Delalutin)-Exposed Cohort and Matched Unexposed Cohort, Olmsted County, Minnesota, 1936-1974 Exposed Outcome

Unexposed (n = 1218)

(n = 609)

No.

%

No.

%

9 59

1.5 9.7

14 55

1.2 4.5

18 Neonatal death Any major anomalya 38 Any anomaly 166 Including hydrocele Excluding hydrocele 151 Genitourinary anomaly 57 Including hydrocele Excluding hydrocele 22 7 Anomaly of female genitalia 14 Anomaly of male genitalia 5 Hypospadias 7 Abnormal testis 13 Central nervous systern anomaly (including spina bifida occulta and sinus tract abnormalities) 4 Major central nervous system anomaly 5 Major cardiovascular anomaly 32 Inguinal hernia

3.0 6.2

12 52

1.0 4.3

27.3 24.8

294 265

24.1 21.8

9.4 3.6 2.3

94 28 10

7.7 2.3 1.7

4.5

16

2.6

1.6 2.3 2.1

11

6 25

1.8 1.0 2.1

0.7

7

0.6

0.8

12

1.0

5.3

54

4.4

Stillbirth Birthweight < 2500 gm

a Anomalies were classified as major or minor after the list of anomalies reported in appendix 2 of Heinonen et a1. 13

The effects on the fetuses were generated by doses sufficient to produce maternal weight 10ss.22 One laboratory study of the effects of Delalutin on mice reported no significant increase in malformations. 23 The doses used ranged from 10 to 200 times human therapeutic doses and were high enough to cause some maternal mortality. Neither the higher frequency of undescended testes in the latter study nor that among our exposed offspring was statistically significant. Undescended, or otherwise abnormal, testes are not included among the multitude of human malformations other investigators have reported to be associated with progestin exposure. The appearance of an excess frequency of undescended testes among exposed offspring in the present study is, therefore, best interpreted as a chance observation, rather than a hazard of progestin exposure. The total incidence of anomalies among both exposed and unexposed cohorts in this study may appear high, compared with other reported rates. 518

Resseguie et aI. Malformations after progestin exposure

No special significance should be attached to this observation, because every reported frequency of anomalies is affected by the information available to the investigators and by their criteria for acceptance of anomalies. Few of 'the anomalies included in the present study appeared on the birth certificate. Many were diagnosed years after birth. The anomaly rates in this article should be greater because of the extended period of followup that was available for both the exposed and unexposed cohorts. Conversely, very careful examination of individuals for the express purpose of detecting anomalies can yield incidence rates greater than those in this report. Smith and Bostian24 examined 100 infants chosen to avoid bias in their estimate of the incidence of anomalies and found 7% to have major anomalies. The present study had access to extensive medical records, but most of these notes resulted from routine examinations or investigations of specific complaints, rather than a deliberate effort of the physician to find and record every possible anomaly. Sweet et al. 25 reported the incidence of hypospadias as 8.2 per 1000 live male births and noted that previous reports spanned the range from 0.8 to 7.6. This variation was attributed to differing methods of case ascertainment and underreporting of minimal cases of hypospadias. The incidence of hypospadias in the present study is higher yet. This difference also probably reflects differing methods of case ascertainment. Valid comparisons of the incidence of anomalies can be made only when the methods of ascertainment are identical for all groups being compared. In the present study the ascertainment of anomalies in both the exposed and unexposed cohorts were accomplished by the same means and in ignorance of the exposure status of the offspring. Based on the results of this study, it appears that developmental anomalies have not been caused by progestins used without other sex hormones in actual obstetric practice at the Mayo Clinic. However, the possibility of interference with descent of the testes cannot be totally excluded. These findings are most reassuring for 17o:-hydroxyprogesterone caproate but cannot be extended to agents such as the 19-nortestosterone derivatives, which are almost unrepresented in the data. Neither can these findings be extended to the use of multiple hormones such as the very common combination of a progestin with an esFertility and Sterility

trogen. Last, the findings need not apply to doses beyond the level commonly used during the study period.

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12. Dixon WJ (Ed): BMDP Statistical Software. Berkeley/Los Angeles, University of California Press, 1981, p 576 13. Heinonen OP, Slone D, Shapiro S: Birth Defects and Drugs in Pregnancy. Littleton, Massachusetts, Publishing Science Group, Inc., 1977, p 446 14. Neto RM, Castilla EE, Paz JE: Hypospadias: an epidemiological study in Latin America. Am J Med Genet 10:5, 1981 15. Mau G: Progestins during pregnancy and hypospadias. Teratology 24:285, 1981 16. Hadjigeorgiou E, Malamitsi-Puchner A, Lolis D, Lazarides P, Nocolopoulos D, Kaskarelis D: Cardiovascular birth defects and antenatal exposure to female sex hormones. Dev Pharmacol Ther 5:61, 1982 17. Matsunaga E, Shiota K: Threatened abortion, hormone therapy and malformed embryos. Teratology 20:469, 1979 18. Ferencz C, Matanoski GM, Wilson PD, Rubin JD, Neill CA, Gutberlet R: Maternal hormone therapy and congenital heart disease. Teratology 21:225, 1980 19. Varma TR, Morsman J: Evaluation of the use of Pro lutondepot (hydroxyprogesterone hexanoatel in early pregnancy. Int J Gynaecol Obstet 20:13, 1982 20. Revesz C, Chappel CI, Gaudry R: Masculinization of female fetuses in the rat by progestational compounds. Endocrinology 66:140, 1960 21. Takano K, Yamamura H, Suzuki M, Nishimura H: Teratogenic effect of chlormadinone acetate in mice and rabbits. Proc Soc Exp BioI Med 121:455, 1966 22. Sannes E, Lyngset A, Nafstad I: Teratogenicity and embryotoxicity of orally administered Iynestrenol in rabbits. Arch Toxicol 52:23, 1983 23. Seegmiller RE, Nelson GW, Johnson CK: Evaluation of the teratogenic potential of Delalutin (17 alpha-hydroxyprogesterone caproate) in mice. Teratology 28:201, 1983 24. Smith DW, Bostian KE: Congenital anomalies associated with idiopathic mental retardation. J Pediatr 65:189, 1964 25. Sweet RA, Schrott HG, Kurland R, Culp OS: Study of the incidence of hypospadias in Rochester, Minnesota, 19401970, and a case-control comparison of possible etiologic factors. Mayo Clin Proc 49:52, 1974

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