Ms. Esplin et al., MYOTONIC-DYSTROPHY IS A SIGNIFICANT CAUSE OF IDIOPATHIC POLYHYDRAMNIOS, American journal of obstetrics and gynecology, 179(4), 1998, pp. 974-977
OBJECTIVE: Myotonic dystrophy, the most common form of muscular dystro
phy seen in pregnant women, may be a significant cause of middle trime
ster polyhydramnios. Our purpose was to determine the prevalence of my
otonic dystrophy in women with idiopathic polyhydramnios and to charac
terize the ultrasonographic findings associated with cases, STUDY DESI
GN: We examined the cases of 67 patients who were delivered of infants
at the University of Utah between 1992 and 1996 with a diagnosis of i
diopathic polyhydramnios (amniotic fluid index >25). Women with diabet
es mellitus, hydrops, or fetal anomalies known to cause polyhydramnios
were excluded from the study. Amniotic fluid samples or cord blood sa
mples were obtained from 41 patients, and polymerase chain reaction am
plification and Southern blot analysis were performed to detect the pr
esence of the myotonic dystrophy mutation. Ultrasonographic findings,
prenatal course, and neonatal outcomes were reviewed in all cases. RES
ULTS: Four of the 41 patients tested had the myotonic dystrophy mutati
on, yielding a prevalence in our population of 9.7%. Three of the 4 pa
tients reported a family history of myotonic dystrophy. Ultrasonograph
ic findings associated with a positive result included abnormal postur
ing of extremities (3/4) and unilateral clubbed foot (3/4). No other s
tructural or growth abnormalities were seen. Two of the patients were
delivered before term, 1 at 26 weeks and 1 at 32 weeks. Three of the 4
infants were severely affected, necessitating admission to the intens
ive care unit, and 1 died on day 11 after birth. One infant, whose myo
tonic dystrophy mutation consisted of between 800 and 900 triplet repe
ats, did not require admission to the intensive care unit. CONCLUSION:
Myotonic dystrophy may be seen as idiopathic polyhydramnios and shoul
d be considered as part of the differential diagnosis in these cases.
Women with a familial history of myotonic dystrophy or ultrasonographi
c evidence of hypotonia, including positional abnormalities of the ext
remities, should be offered deoxyribonucleic acid testing for the myot
onic dystrophy mutation.