A case-comparison study of pregnant women with mitochondrial disease - what to expect?

Objective: Mitochondrial disease is a disorder of energy metabolism that affects 1 in 4300 adults in the UK. Pregnancy is associated with physiological demands that have implications for energy metabolism. We were interested to know how pregnancy was affected in women with mitochondrial disease, particularly those with the most common pathogenic mutation m.3243A>G.

Design: Retrospective case-comparison study.

Population/setting: Sixty-seven women with genetically confirmed mitochondrial disease from the UK Mitochondrial Diseases Cohort and 69 unaffected women participated.

Methods: Participants answered questionnaires regarding each of their pregnancies. Patients were divided into two groups according to genetic mutation, with those harbouring m.3243A>G comprising a single group.

Main outcome measures: Pregnancy-related complications, mode of delivery, gestational age and birthweight of newborns.

Results: Of 139 live births in the comparison group, 62 were in the m.3243A>G group and 87 were in the 'all other mutations' group. Pregnancies of women with the m.3243A>G mutation had significantly more gestational diabetes (odds ratio [OR] = 8.2, 95% CI 1.3-50.1), breathing difficulties (OR = 7.8, 95% CI 1.0-59.1) and hypertension (OR = 8.2, 95% CI 3.1-21.5) than the comparison group. Only half of the pregnancies in the m.3243A>G group had normal vaginal delivery, with emergency caesarean section accounting for 24.2% of deliveries. Babies were born significantly earlier to mothers harbouring m.3243A>G with 53.3% of them preterm (<37 weeks). These babies were also more likely to require resuscitation and admission.

Conclusion: Women who carried the m.3243A>G mutation appeared to be at higher risk of complications during pregnancies, caesarean section and preterm delivery than the unaffected women or those with other forms of mitochondrial disease.

Tweetable abstract: Pregnant women with mitochondrial disease - m.3243A>G mutation - are at greatly increased risk of complications and preterm delivery.