"I'd love to have a boy and a girl twin! That would just be ideal. Is there any way to make this happen?"
If your multiples are the result of an invitro fertilization, you may have an opportunity to select the gender. Two procedures are currently available. While neither one is completely foolproof, they do greatly increase your odds of obtaining the desired outcome. The first is called sperm sorting. A sample of sperm from the father is put through a cytometer to identify and separate cells bearing an X (male) or a Y (female) chromosome. The sorted sperm are used for artificial insemination or invitro fertilization. The success rate is estimated at about 80%; your odds are slightly better if you want to conceive a girl.
Alternatively, pre-implantation genetic diagnosis (PGD) offfers a better than 95% chance of success. Originally developed as a way to test embryos for genetic disorders, PGD is performed after the egg and sperm are joined, but before the embryo is transferred to the mother's uterus. A single cell is removed and its chromosomes analyzed to determine the gender of the embryo. But reliable results don't come cheap. The cost of the process adds thousands of dollars to the already expense experience of invitro fertilization.
Gender Selection and Unassisted Conception
Not all twins and multiples are the result of reproductive technology. But unassisted conceptions don't offer as much opportunity for infallible results. While many parents claim success using the Shettles method of timing intercourse to coincide with a predetermined ovulation schedule, this coordinated conception model has no impact on twinning.
If you are predisposed to having twins anyway, the method might achieve the desired results, as long as you're after same sex twins. There are two types of same sex twins. Monozygotic twins are always two children of the same gender, as they develop from a single fertilized egg. On the other hand, two-thirds of dizygotic, or fraternal, twins will be either girl/girl or boy/boy sets. These multiples develop from two separate fertilized eggs. In either case, timing intercourse to promote the prevalence of male- or female-producing sperm only increases your chances of having more than one baby of the preferred gender.
Should you choose the sex of your babies?
The issue of gender selection is fraught with ethical implications. Are you playing God? Should medical technology leave well enough alone? Does the practice of gender selection promote sexual discrimnation? Or does it offer an opportunity for parents to create the ideal family, especially when they may only have a single shot at conceiving a baby?