"It's twins," my friend reported, full of relief. At the age of 43, this was a miracle for her. Her pregnancy was a medical marvel, as well. She had endured a year of thermometers, hormone injections and dashed hopes before finally becoming pregnant by in vitro fertilization.

My friend had 5 embryos implanted in her uterus. The hope was that at least one of these would "take". The risk was that all would "take", endangering her and all 5 fetuses. Until she knew exactly how many babies she was carrying, she agonized over what to do.

Her doctor advised her to abort all but 2 fetuses, if that were necessary. A mother her age could carry 2 babies nearly to full term, but not 3, she was told. She ran the risk of severe complications and her babies could be born very prematurely, with potentially disastrous consequences to their health.

She shuddered at the story of the octuplets whose survival was always uncertain and whose health problems were tragic. She knew what her decision would be if there were 4 or 5 fetuses, but what about 3? Giving these babies the best possible chance to be born healthy was her top priority. Thankfully for my friend, twins meant she didn't have to go through an abortion. But, all along she knew she would have that choice if it were necessary to save her other babies.

Medical and scientific advances have changed our world forever. There is no going back to the less complicated decisions of yesteryear before fertility drugs, in utero surgery and organ transplants. Cloning, nascent gene therapies and the human genome project have moved us to a new threshold of difficult ethical decisions regarding medical treatment and life, itself.

Already, parents can decide about whether to carry to term or abort a fetus that is severely handicapped or likely to suffer a life-threatening genetic disorder. This, in itself, is a terrible decision for parents to make. Nonetheless, they have the right to make that choice. But, what if they want a boy and the fetus is a girl? For me, the ethical boundaries on that one are crystal clear. But, who gets to decide? And, how do we set the boundaries within which such decisions are made?

What about the looming potential of genetically engineering your child? So that she is smart and beautiful, with the sparkle of Oprah and the voice of Beverly Sills? Does it make a difference if, instead, you change your child's genes to eliminate a predilection for heart disease or diabetes or to remove a deadly gene?

Stunning advances in medicine have brought us enormous opportunities to improve our lives. They have also brought us ethical dilemmas that test the very fabric of our value systems. If we can ease human suffering, why wouldn't we do it? What are the consequences of relieving that suffering or of preventing it from happening in the first place? Will we remake humankind in a more perfect form only to have disastrous results in some unimagined way? Who gets to have access to medical miracles when the costs are very high?

These and so many more questions are very troubling. There are no easy answers. Some questions must be answered by each individual or family, such as what action to take about a dangerous pregnancy. Others must be answered by our society at large, such as what guidelines are appropriate for gene therapy and genetic engineering.

I worry that we don't have adequate mechanisms in our society for having this debate. We polarize ourselves around pieces of medical ethics when some of the larger and more frightening issues go unresolved. It is critical that we discuss these ethical dilemmas not just in hospitals and doctors' offices and universities, but in schools and clubs and places of worship and our own homes. It is not good enough to cite "tried and true" precepts. Some work in today's complicated world and some do not. As a society, we must have a broad and informed debate about these momentous issues, a debate that will indeed shape the future of humankind.