This document discusses the effects of hyperthermia, or abnormally high body temperature, during pregnancy. It notes that brief fever episodes are not associated with birth defects, but that a core temperature over 102.2°F for 24 hours or more during gestational days 14-28 can increase risks of central nervous system defects in the embryo. The mechanisms by which heat exposure causes defects and the specific defects linked to different gestational periods are described. Guidelines are provided for limiting hot tub exposure to under 15 minutes in 29°C water or 10 minutes in 40°C water to avoid potentially teratogenic temperatures. The document concludes by noting decreased fertility has been linked to occupational heat exposure in both females and males.

1. HYPERTHERMIA IN PREGNANCY
PARK SUE YEON
Division of Maternal-Fetal Medicine Fellowship.
Department of Obstetrics and Gynecology.
Cheil General Hospital and Women’s healthcare center.
Kwandong University College of Medicine.

2. HEAT
• Heat
– Form of energy associated with kinetic motion of molecules
– Radiation, conduction or convection
– HEAT, HEAT STRESS, or HYPERTHERMIA
• Total net heat load on the body
• Occupational exposure recommendations
• Physiological effects of heat
– Dukes-Dobos(1981), NIOSH Criteria Document (NIOSH, 1972)
– Exclude microwave radiation
• SOURCES
– Outdoors in hot climates, Indoors with poor ventilation
– Wearing heavy protective clothing, hot industrial processes

3. EFFECTS OF ACUTE
EXPOSURE
• Response
 Rising in core body temperature
 Increase in heart rate
 Water and salt loss from excessive sweating
• Heat illness
1) Heat cramps : loss of salt
2) Heat exhasution
3) Heat stroke
 Exceeds 41.1 degrees C (106 degrees F)
 failure of the thermoregulatory processing body temperature
 Immediate removal to a cool environment, cooling measures, and medical
supportive care
4) Dehydration, electrolyte imbalance, skin rashes, heat edema, loss of
mental and physical work capacity

4. EFFECTS OF CHRONIC
EXPOSURE
• Acclimatization
– Decrease in the heart rate
– Decrease in internal body temperature
– Increased sweating
• Variation of acclimatization
– Dry heat versus wet heat
• Loss of acclimatization
• Prickly heat :
– form of dermatitis
– Blockage of the sweat glands
• Heat cataracts

5. GENETIC EFFECTS
• DNA DAMAGE/REPAIR
– Radiated heat : form of electromagnetic radiation
1) Increase in preimplantation losses
2) Chromosome abnormalities
3) Sister chromatid exchange
4) DNA polymerase was inactivated.
5) Double-strand DNA breaks in cultured Chinese hamster ovary cells

6. REPRODUCTIVE EFFECTS IN HUMA
N
• High fever in pregnancy and birth defect
 Core body temperature : 39 degrees C (102.2 degrees F)
 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

7. REPRODUCTIVE EFFECTS IN HUMA
N
• Definition of hyperthermia
• Abnormally high body temperature: at least 38.3 ºC (101ºF) or
higher
• Normal body temperature : 37ºC (98.6ºF)
• Causes
• Fever due to infection (viral or bacterial )
• Hot tubs or very hot baths
• Saunas
• Electronic blankets
• Heavy exercise on hot and humid environments

8. REPRODUCTIVE EFFECTS IN HUMA
N
• Teratogen
 Stage of embryonic development at the time of exposure
• Pre-implantation period
• After implantation
 Degree of temperature elevation, and its duration
• Threshold temperature for teratogenicity
:38.9 ºC (102ºF)

9. REPRODUCTIVE EFFECTS IN HUMA
N
• Development
1) Pre-implantation period (∼3 weeks)
Increased pre-implantation loss due to failure to
implantation or embryonic death
2) Embryonic period
 period of major organogenesis (3∼8 weeks)
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

10. • 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
REPRODUCTIVE EFFECTS IN HUMA
N

11. •Neural plate and neural tube stages
•Neural tube, eye, face, heart, and vertebral formation
•Embryo is susceptible to damage of heat
•Brain : anencephaly, exencephaly, spinabifida and encephalocele
•Eyes : anophthalmia, microphthalmia, defects of the iris
•Face : small upper or lower jaws, cleft of the face
•Heart
•After neural tube closes to form the brain and spinal cord
Vertebrae and ribs become susceptible to damage
REPRODUCTIVE EFFECTS IN HUMA
N

12. REPRODUCTIVE EFFECTS IN
HUMAN
• Hot tub
– Measured vaginal temperatures of 20 non-pregnant
women while in hot tubs and saunas
– Use of hot tubs for limited time : 10-15 minutes
(Harvey et al., 1981)
– Hot tub set at 40°C until their temperatures reached 39°C
with 54% of the subjects not feeling uncomfortably hot
– A study of 24 Australian women
(Ridge and Budd, 1990)

13. SAUNA BATHING
• Sauna bathing dose not seem to be associated with
adverse effects.
– 301 pregnant women
a. The high-fever group: 102°F(38.9ºC) 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)
• limit exposure in the hot tub
– 15 minutes in 29 degrees centigrade
– 10 minutes in 40 degrees water.
– Shortened if other sources of temperature elevation are present (e.g.
fever, exercise)
(Chambers et al., 2006)

14. REPRODUCTIVE EFFECTS IN
HUMAN
• Electric blankets or heated water beds
• 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

15. 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

16. FERTILITY EFFECTS-MALE
• FERTILITY DECREASED MALE
• Core body temperature : 38 degrees C (100.4 degrees 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

17. Thank you for your attention!!