Cryopreservation

A 12-page insert in my morning paper offers articles on fertility and pregnancy mixed in with ads from fertility clinics and drug companies. We’ve talked before about various aspects of assisted pregnancy and its implications for non-paternity events. This morning’s insert brings up another aspect – the ability to preserve eggs, sperm and embryos for long periods of time, usually via cryopreservation or freezing.

Preservation itself, one might think, would have no implication for NPEs. However, it offers the opportunity to shift fertilization or pregnancy in time and to create asynchronies in what is usually a synchronous process.

Let’s consider sperm preservation first. Artificial insemination relies, generally, on the preservation of semen samples from donors that are then used to impregnate women. (There are exceptions – a case a few years ago involved a doctor in New Jersey who would ‘generate’ his own ejaculate on the spot and use it to fertilize his patients. He sired quite a few kids before the practice was discovered.) By preserving the semen, a woman may become pregnant with a man’s child after his death. Obviously, this isn’t limited to the artificial insemination case. Sperm is now preserved by in vitro clinics, by men who are about to undergo radiation treatments and by men who are about to go overseas to war in anticipation of injury or incapacity.

There are also new techniques for harvesting viable sperm from the recently deceased, or so the lead article in the insert informs me. The point here is that the recovery and preservation of semen offers the possibility of men siring children long after their own death, and perhaps with women they did not know. Newer technologies that preserve ova offer this same possibility in the case of women.

So how long do frozen sperm and ova remain viable? A Mayo clinic study found no difference in fertility between fresh or frozen sperm, but the freeze interval was not specified. There has been at least one case where sperm frozen for 19 years was used successfully to fertilize an ovum and resulted in a full-term pregnancy. Studies done with other species indicate that sperm frozen in liquid nitrogen (about -322° F) remain viable for remarkably long times – trends in viability decreases indicate that frozen sperm could still be viable after 10,000 years. Ova freezing is a newer technique and viability is not as high as for sperm, although that could improve as studies continue. At least so far, freezing embryos has been more successful than freezing ova.

We have the possibility with these new techniques for children to be born long after their biological parents have died. The imagination reels at the variety of NPEs made possible through intent or accident. What family historian is prepared to tease out actual inheritance when generations could pass between parents and the birth of their children?