Sex in Space: Part Three: No Babies, Please

Contraception would be very important in space, because of limited medical resources for pregnancy and potentially hazardous/deadly effects on embryo (such as increased radiation exposures). No method other than sterilization is 100% effective; the effectiveness of oral contraceptive in microgravity is not known. In microgravity, sperm may linger in vaginal tract, as their movement is not dependent upon gravity: transport by muscle contractions, ciliary activity, and the motility of sperm. On the other hand, microgravity and spaceflight by themselves may have contraceptive effects. Menstrual dysfunction is likely due to disturbance in circadian rhythms, intensive exercise, stress. Disturbance of the hypothalamic-pituitary-ovarian axis lead to lack of ovulation or excessive menstrual bleeding. This may include retrograde menstruation, producing endometriosis and infertility. Male fertility: fall in testosterone level and sperm motility, exposure to toxins used in life-support and propellants could reduce sperm counts.

Higher radiation levels can affect both male and female fertility. Sperm cells are the most radiosensitive in human body, resulting in reduced fertility or genetic abnormalities. Sperm cells produced on a 74-day cycle, so levels return to normal after low radiation exposures. Radiation doses needed to destroy all sperm cells are usually fatal. Ovaries lie 5-7 cm below the skin, so some slight shielding. Oocytes more radio-resistant to genetic defects than are sperm cells, but are not replaced if damaged. In women, a radiation exposure of LD50 (enough to produce 50% fatality rate) results in sterilization (destruction of all oocytes and end to estrogen production) but effects of radiation are cumulative. Radiation can cause endometriosis.