Major malformations in babies whose mothers had pre-existing diabetes during pregnancy

Anita McGrogan, Julia Snowball, Corinne De Vries

Research output: Contribution to journalMeeting abstractpeer-review


Background: Pregnancy outcomes in women with preexisting diabetes are known to be worse than in the healthy population: rates of congenital malformations have been reported to be 2 to 10-fold higher. This is due to poor glycaemic control.
Objectives: To determine rates of congenital malformations in babies of mothers with type1 (DM1) and type2 (DM2) diabetes and compare with the healthy population.
Methods: Patients with pre-existing DM1 or DM2 during pregnancy were identified on the General Practice Research Database using diagnoses, prescribing, use of testing equipment and referral records. Mothers were
matched to babies using registration records with the same family number, within 2 months of delivery date. Major congenital malformations were identified in the baby’s record and malformations verified with at least two related medical records; free text entries were checked.
Results: Between January 1992 and March 2007 1,057 DM1 patients had 1,329 pregnancies and 365 DM2 patients had 441 pregnancies that resulted in a live birth. Eighty-four major malformations were found in 78 babies of DM1 mothers: 41 were cardiac, 11 were urogenital and eight were limb defects. Twenty-six major malformations were identified in 22 babies of DM2 mothers (seven cardiac defects). Overall, 5.9% of babies of DM1 mothers and 5.0% of babies of DM2 mothers had a malformation compared to 2–3% in the healthy population. The malformation rate for babies of DM2 mothers was comparable with another study (5.8%) but was lower for DM1 (8.2%). The proportion of cardiac malformations in
babies of DM1 mothers was three times higher than in the healthy population.
Conclusions: Babies whose mothers had DM1 or DM2 during pregnancy had double the rate of malformations. Pregnancy loss due to malformation has not been included but previous work found a greater proportion of terminations for medical reasons (1% in DM1, 1.8% in DM2) compared to healthy pregnancies (0.8%). Limitations include potentially differential recording of malformations between babies of mothers with DM1 and DM2 and the lack of records of glycaemic control. Differences in rates of malformations between treatments
including analogue and human insulin will be evaluated next.
Original languageEnglish
Article number838
Pages (from-to)388
Number of pages1
JournalPharmacoepidemiology and Drug Safety
Issue numberS3
Publication statusPublished - Aug 2012


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