Different patterns of obstetric complications in myotonic dystrophy in relation to the disease status of the fetus

The obstetric histories of 26 women with myotonic dystrophy (DM), who had a total of 67 gestations, were reviewed retrospectively comparing gestations with affected (DM-fetuses) and unaffected fetuses (UA-fetuses). Second, th e influence of gestation on the disease course and the personal attitude to wards family planning in DM was assessed. Miscarriages and terminations occ urred in 11 pregnancies. Of the 56 infants carried Do term, 29 had or most likely had inherited the gene for DM from their affected mothers at the tim e of investigation; 18 (61%) in this series were affected by the congenital form of DM. Perinatal loss rate was 11% and associated with congenital DM. The rate of obstetric complications was significantly increased in all wom en. However, preterm labor was a major problem in gestations with DM-fetuse s (55 vs. 20%), as was polyhydramnios (21% vs. none). While forceps deliver ies or vacuum extractions were required in 21% of deliveries with DM-fetuse s and only 5% of UA-fetuses, the frequency of Cesarean sections was similar in both groups (24 and 25%). Obstetric problems were inversely correlated with age at onset of maternal DM, while no effect of age at delivery or bir th order on gestational outcome was seen. DNA analysis confirmed the diagno sis in 19 patients by the presence of enlarged CTG repeats (EcoRI-expansion s) on chromosome 19. Of the 17 patients whose CTG repeat length was known, 59% were classified as E2 (corresponding to 500-1000 repeats), 24% as E1 (< 500 repeats), while larger expansions (E3; 1000-1500 repeats, or E4; >1500 repeats) were seen in three patients (17%). Obstetric complications or cong enitally affected children occurred in all maternal phenotypes and CTG; rep eat classes. Eight (31%) patients experienced a worsening of symptoms that was temporary, weight related in three cases, and persistent in five. With the exception of three patients, most new mothers were able to care for the ir families. To conclude, pregnant women with DM need constant obstetric mo nitoring and should be advised to deliver in centres with perinatal facilit ies. Am. J. Med. Genet. 80:314-321, 1998. (C) 1998 Wiley-Liss, Inc.