Steroid contraceptive use and pregnancy outcome

Contraceptive use in relation to pregnancy outcome was studied in 8,816 births in Chiang Mai, northern Thailand, by examination of newborn infants and interviews with their mothers. Four thousand twenty‐three women used no contraception before the index pregnancy, 1,229 used the injectable contraceptive Depo Provera (DMPA), and 3,038 used oral contraceptives prior to or during pregnancy. No differences were observed between these groups with respect to still births, multiple pregnancies, and birthweight. Women who used oral contraceptives had unexpectedly low rates of major defects and may have been affected by self‐selection bias, whereas the noncontraceptors had rates similar to other populations. There was a significantly increased association of polysyndactyly among infants of DMPA users relative to the other groups, which was most pronounced in offspring of women under age 30 years, and persisted after exclusion of subjects with a family history or infants with multiple abnormalities. However, in five out of the ten polysyndactyly, cases, the last injection of DMPA occurred more than 9 months before conception, and only three cases had definite gestational exposure. The association of chromosomal anomalies was also significantly increased in infants of mothers who used DMPA. The unrelated nature of these defects, the lack of confirmation from other studies, the distant preconceptional exposure to DMPA in many cases, and chance effects due to multiple statistical comparisons make a causal association unlikely. Other birth defects that had been previously reported in some publications to be associated with progestational steroid exposure, such as neural tube defects, heart malformations, and limb reduction defects, were not found in this study. Further research should evaluate in detail the type and incidence of syndactyly or chromosomal aberrations in exposed groups and appropriate control populations.