This study aims to better characterize the risk linked to metformin use during pregnancy, using a prospective multicentric cohort design enabling a large sample size, in evaluating the rate of birth defects after first trimester exposure, as well as several other pregnancy related outcomes.

Inclusion Criteria:

• Exposed group: exposed to metformin (Anatomical Therapeutic Chemical A10BA02) any time during pregnancy (i. e. any time from conception to week 42 after last menstrual period (LMP)).
• Reference group: at no time during pregnancy were exposed to metformin, insulin or any other hypoglycaemic agent.

Exclusion Criteria:

• exposed to any of the following known major teratogen or major fetotoxicant: acitretin, isotretinoin, mycophenolate, thalidomide, valproic acid, angiotensin-II receptor blockers (only when used in 2nd or 3rd trimester), ACE inhibitors (only when used in 2nd or 3rd trimester), or (b) following treatment indications coded: malignancies (MedDRA code: malignant or unspecified tumors (SMQ 20000091), ICD-10: C00-D09)) or malignancy related conditions (MedDRA: SMQ 20000092), ICD-10: C00-D09).
• lost to follow-up

Patient from the European Network of Teratology Information Services (ENTIS) Cohort. This cohort is composed with patients, seeking counseling on the safety and risks regarding medication exposures in the reproductive age by themselves or through their healthcare provider. Each center gathers structured information on the exposure (medication, time of exposure, dose), maternal demographics, as well as medical and obstetric histories is collected prospectively. After the estimated date of birth, follow-up information on pregnancy outcome, gestational age at delivery, birth weight, congenital anomalies and neonatal complications is gathered through structured telephone interviews and/or mailed questionnaires sent to the mothers or their healthcare providers.