Table 1 Characteristics of the included case reports

Characteristic of pregnant woman

26-year-old Japanese

gravida 3, para 0

Monochorionic-diamniotic twins

32-year-old

primigravida

Singleton pregnancy

31-year-old

Caucasian

Primigravida

Singleton pregnancy

30-year-old

Japanese

Primigravida

Singleton pregnancy

35-year-old

Primigravida

Singleton pregnancy

34-year-old

Singleton pregnancy by IVF-ET

Past medical history

No history of significant medical or surgical history, and no history of neuromuscular disease

Maternal congenital myotonic dystrophy

No history of neuromuscular disorders, alcoholism and drug abuse.

No history of surgical, neuromuscular disorder. Had history of taken alprazolam (0.4 mg/day) prior to conception because of dysautonomia.

Had type II diabetes mellitus. Clinically diagnosed as myositis of unknown etiology or an atypical form of polymyositis at 21^6/7 GW

Endometrial cancer

Why and when use ritodrine

Increasing contractions that every 7 to 8 min at 23^2/7 GW.

Premature labor at 31 GW

Premature labor at 28 GW

Diagnosed as placenta previa and mild uterine contractions at 23 GW. Diagnosed vaginal bleeding and frequent uterine contractions at 29^3/7 GW

Regular uterine contractions with cervical length shortening to 17 mm at 29^6/7 GW

Irregular contractions at 32 GW

Dosage of ritodrine

23^2/7 GW: IV, 100 μg/min

24^2/7 GW: IV, 200 μg/min

31 GW: po, 15 mg/day, initially.

28 GW: po, 300 mg/day. 32 GW: IV, 100 μg/min for 2 days. 32^2/7 GW: IV, 50 μg/min for other 2 days. 32^4/7 GW: po, 600 mg/d for 1st day. 32^5/7 GW: po, 800 mg/d for the following 3 days, and then at 300 mg/day.

23 GW: po, 15 mg/day, initially.

29^3/7 GW: IV, 50 μmg/min.

29^6/7 GW, IV, 67 μg/min.

32 GW, IV, 100 mg

Drug combination

MgSO₄

/

/

Stopped use ritodrine and started use MgSO₄ (1 g/h).

/

Penicillin, dexamethasone

Gestational age on ADR appeared

28^1/7 GW

31^3/7 GW

29 GW

29^3/7 GW

29^6/7 GW

32 GW

Symptoms

Slight muscle pain in the lower extremities at 28 GW. Muscle pain increased and dyspnea occurred at 28^6/7 GW

No evidence of any worsening of the myotonic symptoms.

Mild muscle pain at upper and lower limbs and generalized weakness at 29 GW. After 33^1/7 GW, muscle pain and weakness worsened. The patient became could neither stand, nor walk at 36 GW.

Extreme muscle pain in the upper and lower limbs and general weakness at 29^3/7 GW.

Severe muscle pain in the limbs appeared after ritodrine administration 3 hours.

Local pain appeared after 9 hours of treatment as long as the front thigh bended, which would disappeared as long as straightening. One hour later, emergency cesarean section was performed due to fetal distress. The muscle pain of lower limbs increased after cesarean section. The urine was slightly darker and yellow.

Laboratory tests

28^1/7 GW: CK 322 IU/L; AST 86 IU/L; ALT 102 IU/L;

28^6/7 GW: CK 1167 IU/L, Mb(blood) 280 ng/mL. Mb(urinary) 12 ng/mL.

Urinalysis was positive for occult blood and revealed 3–4 red blood cells/field and positive granular casts.

SpO2 90%.

CPK 10,897 mg/dl, and myoglobinuria (1800 ng/dl)

36 GW: CK 25000 UI/L; AST 150 UI/L; ALT 140 UI/L. Mb(urinary) 2.3 ng/dl.

Before the IV administration: CK 7200 IU/L; CK-MB 208 IU/L; AST 163 IU/L; ALT 74 IU/L; LDH 536 IU/L.

The next day of the IV administration, CK 87300 IU/L; CK-MB 2040 IU/L; AST 1164 IU/L; ALT 248 IU/L; LDH 3380 IU/L; Mb(blood) 11,200 ng/mL; Mb(urinary) 615 ng/mL.

29^6/7 GW: CPK 32019 U/L. myoglobinuria.

On the first postpartum day, Mb>3838 ng/mL, troponin 0.078 ng/mL, CK 20555 U/L; LDH 1229 U/L, CK-MB 248 U/L; ALT 51.4 IU/L; AST 333 IU/L; Urinalysis was positive for occult blood (3+)

Outcomes of infant

28^6/7 GW performed an emergency cesarean section. Both infants exhibited respiratory distress syndrome, both did well after extubation with no other problems

Spontaneously delivered a healthy male baby at 37 GW

The woman underwent operative delivery, the baby was normal without peri-partum sufferance.

An emergency cesarean section was carried out at 29^5/7 GW. The neonate was admitted to the neonatal intensive care unit due to immaturity, and had respiratory distress syndrome, patent ductus arteriosus and ventricular septal defect. The blood CK level was 799 IU/L.

An emergency cesarean section was carried out at 31^6/7 GW. After birth, the infant was diagnosed with myotonic dystrophy

Emergency cesarean section was performed due to fetal distress after 10 h of administration. The postnatal condition of the fetus was not described.

Outcomes of pregnant woman

On the third postpartum day, maternal oxygenation had improved, and oxygen administration was discontinued. In addition, the muscle pain disappeared, and CK, AST and ALT levels normalized soon after delivery

The laboratory data improved gradually with the serum CPK levels at 955 mg/dl. (Her serum CPK levels at admission was 1919 mg/dl)

In one month, she could stand and walk again without help, but a mild weakness still persisted at girdle muscles. Levels of blood CK were still high (7000 UI/L). Three months later, both neurological assessment and CK levels were normal

the muscle pain disappeared, and CK, AST, ALT, LDH, and blood myoglobin levels normalized soon after delivery. On the eighth postpartum day, the laboratory data improved gradually and the CK levels were at 107 IU/L

The muscle pain soon disappeared and the elevated CPK and myoglobinuria immediately resolved

The muscle pain disappeared after 2 days of postpartum. Mb 1154.6 ng/mL; troponin 0.039 ng/mL; CK 28020 U/L; CK-MB 272 U/L； LDH 1064 U/L; ALT 99.2 IU/L; AST 538 IU/L; Urinalysis was positive for occult blood (3+). The laboratory test was normal after 7 days of postpartum.