In-vitro fertilization involves the fertilization of an ovum from a woman with that of the sperm of her partner in a laboratory rather than it happening naturally. It is difficult to think of any moral or ethical concerns in having a child using in-vitro fertilization. The procedure does not involve the use of sperm from a man not married to the woman as in the case of the use of sperm from a donor that is taken from a sperm bank nor is the fertilized egg transplanted into the uterus of a woman willing to conceive the child for the couple by having the embryo implanted in her uterus, also called a surrogate mother.
In-vitro fertilization is simply a procedure where a doctor either helps a woman who can produce healthy ovum but whose body does not allow their fertilization naturally or choses a healthy sperm from the many sperm cells that are produced by the man to ensure a successful natural fertilization of the egg and creation of the embryo. In short the doctor extracts a healthy egg and choses a healthy sperm that is used to fertilize it in a test-tube; the embryo created is then placed in the uterus of the woman from whom the egg was taken.
1) Because IVF involves fertilizing a dozen or more eggs of which only a few are implanted and the rest are destroyed. From a pro-life standpoint, a zygote (fertilized egg) is considered living, even though only one cell. The disposal of several zygotes is really the same as several early abortions, just outside the womb.
Also, there's about a 1 in 5 chance of survival for the zygote. 12 conceptions for a 20% chance of survival? Those are really low odds. If, perchance, multiple embryos grow inside the womb, the mother may choose to selectively abort.
2) If the zygotes AREN'T thrown away, they're stored in a freezer and used for later use for, say, a couple that has insufficient sperm or eggs and can't have a baby with their own DNA. Many times they're forgotten over time and abandoned. Not to mention, there's also the question of the parents- would the sperm and egg donators (the real parents) have legal rights over the child if born?
*This is a pro-life point of view. Someone pro-choice probably wouldn't find anything conceptually wrong with IVF if they didn't believe life starts at conception. It's really all a matter of opinion and belief, but for the purposes of this question, I answered with the assumption that a fertilized egg is a living human being.