HYPERTHERMIA IN PREGNANCY

PARK SUE YEON

.

HEAT• Heat, Heat stress, Hyperthermia

• Form of energy associated with kinetic motion of molecules

• Radiation, conduction or convection

• Total net heat load on the body

• Physiological effects of heat • Dukes-Dobos(1981), NIOSH Criteria Document (NIOSH, 1972)

• Exclude microwave radiation

• Source• Outdoors in hot climates, Indoors with poor ventilation

• Wearing heavy protective clothing, hot industrial processes

EFFECTS OF EXPOSURE

ACUTE EXPOSURE

Response① Rising in core body

temperature

② Increase in heart rate

③ Water and salt loss from excessive sweating

Heat illness1) Heat cramps : loss of salt

2) Heat exhasution

3) Heat stroke (41.1 °C ,106 ºF ↑)

Dehydration, electrolyte imbalance, skin rashes, heat edema, loss of mental and physical work capacity

CHRONIC EXPOSURE

Acclimatization① the heart rate ↓

② internal body temperature↓

③ Increased sweating

Variation of acclimatization • Dry heat versus wet heat

Loss of acclimatization

Heat cataracts

GENETIC EFFECTS

• DNA Damage/Repair• Radiated heat

• Form of electromagnetic radiation

• Interact with the genetic material

• Increase in preimplantation losses

• Chromosome abnormalities

• Sister chromatid exchange

• DNA polymerase was inactivated.

• Double-strand DNA breaks in cultured Chinese hamster ovary cells

REPRODUCTIVE EFFECTS IN HUMAN

• High fever in pregnancy and birth defectNormal body temperature : 37ºC (98.6ºF)

Core body temperature : 39 °C↑ (102.2 ºF)

Gestational days 14 to 28

Central nervous system • Microcephaly

• Hypotonia, Microopthalmia, Anencephaly and Occipital encephalocele

• Meningomyeloceles and Spina bifida(GA 25-28)

Spontaneous abortions

• Brief fever episode • No association in birth defects or decreased intelligence

• Acclimatization • Reduce the risk of CNS defects

REPRODUCTIVE EFFECTS IN HUMAN

• Definition of hyperthermia• Abnormally high body temperature: at least 38.3 ºC (101ºF) or ↑

• Causes • Fever related source

• Infection (viral or bacterial )

• Non Fever related source • Hot tubs or very hot baths • Saunas• Electronic blankets• Heavy exercise on hot and humid environments

• Teratogen Stage of embryonic development at the time of exposure Degree of temperature elevation, and its duration

• Threshold temperature for teratogenicity :38.9 ºC (102ºF)

• Development

1) Pre-implantation period (∼3 weeks)

Increased pre-implantation loss due to failure to implantation or embryonic death

2) Embryonic period (3∼8 weeks)

Period of major organogenesis

Especially, susceptible to the induction of developmental defect

CNS, skeletal, neuromuscular, and cardiac defect

3) Fetal periods (8 weeks~)

Results mainly in reduced growth & functional defects

• Mechanisms of defects

Apoptotic cell death

=> NTD, Microencephaly

Disturbance of neural crest cell and neuronal cell migration

=> Defects in heart and face

Hirschsprung disease, ectopic nests of neurons in the brain

Behavioral deficits and reduction in IQ

Damage to cell membrane

Damage to blood vessels & placenta

• Hypoplasia of limbs & toes(hypodactyly), exomphalos,

gastroschisis, possibly abortion and fetal growth restriction

• National Birth Defects Prevention Study Duong et al.2011

• Evaluation of risk for hot tub

• 20 healthy nonpregnant volunteers in hot tub heated to 39-41 ºC

• Measured vaginal temperatures while in hot tubs and saunas

• Leave to hot tub : 39 ºC ( 10 minutes) , 41.1 ºC(5 min)

• Maximum temperature and duration : no more than 15min at 39ºC

Harvey et al., 1981

• A study of 24 Australian women

• Hot tub set at 40°C until their temperatures reached 39°C with 54% of the subjects

not feeling uncomfortably hot

Ridge and Budd, 1990

HOT TUB

SAUNA BATHING

• Sauna bathing dose not seem to be associated with adverse

effects.

• 301 pregnant women

a. The high-fever group: 38.9 ºC (102°F) or above for at least 24 hr

b. The low-fever group: less than 102°F for any length of time, or a fever of 102°F

or above for less than 24 hr

• women in the high-fever group demonstrated a significantly increased rate of

major malformations

Chambers et al., 1997

RECOMMENDATION

• Environmetnal cuase

• Pontentially preventable

• Avoid and minimize risk

• 2005 Center for Disease Control and Prevention for reprouductive age

women

① Take 400 ug of supplemental folic acid

If Use hot tubs or spa

② Possibility to unkowingly be pregnant

③ Limit exposure in hot tub to < 15 min in 39 ºC and <10 min in 40ºC

④ Risk factor : not in good healthy, previously being in the hot tub or spa, fever,

exercise, or another source of hyperthermia, or begins to feel uncomfortable

• A woman who is or could be pregnant should be aware of the possible

variability in hot tub or spa temperature Chambers et al., 2006

• Study of children of New York

• No association between use electric blanket s or heated water beds and

incidence of cleft palate, cleft lip, or neural tube defects

• Exposed to 60-cycle

Dlugosz et al,1992

• The change thermoregulation during pregnancy

Change in the subjective perception of heat

Insufficient occupational data

ELECTRIC BLANKETS OR HEATED WATER BEDS

FERTILITY EFFECTS-FEMALE

• FERTILITY DECREASED FEMALE

• Physiological effects of heat on women

• Menstrual cycle

• Less adaptable to heat than men

• Women working in hot environments

• Increases uterine vascular resistance

• Decreases blood flow in high risk pregnancy

• No effect in normal pregnancy controls

FERTILITY EFFECTS-MALE

• FERTILITY DECREASED MALE

• Core body temperature : 38 ºC (100.4 F)

• Increase sperm abnormalities and infertility in the male

• Occupational study

• Increased risk of delayed conception , suggesting a weak effect

on male fertility.

• The temperatures were higher than those to which welders are

normally exposed