Sex selection
Sex selection is the attempt to control the sex of the offspring to achieve a desired sex. It can be accomplished in several ways, both pre- and post-implantation of an embryo, as well as at childbirth. It has been marketed under the title family balancing.
According to the United Nations Population Fund, the reasons behind sex selection are due to three factors and provide an understanding for sex ratio imbalances as well as to project future trends. These factors are:
- A preference for sons which stems from household structures "in which girls and women have a marginal social, economic and symbolic position, and consequently enjoy fewer rights." These household structures also focus on security in which sons are expected to provide support to their parents throughout their life;
- Technological growth of prenatal diagnosis which allows parents to know the sex of their unborn child; and
- Low fertility which increases the need for sex selection by reducing the probability of having a daughter in smaller families.
Preference for sex of child
In many cultures, male offspring are desired in order to inherit property, carry on the family name and to provide support for parents in old age.In countries such as India, China, Indonesia and Nepal sons have been favored over daughters. According to a 2018 Gallup poll, American parents favor boys by a 36% to 28% margin. The results were similar to a survey in 1941, when Americans preferred a boy to a girl by a 38% to 24% margin. The overall preference was driven by men, of whom 43% preferred a son compared to 24% who preferred a daughter. Men's preference for sons was most pronounced among men aged 18 to 29. Women, on the other hand, showed no preference for either sex, with 31% stating that they preferred a girl and 30% responding that they favored a boy.
A 2009 study at the University of Ulster found that having sisters, as compared to brothers, can enhance the quality of an adult's life.
Cultural son preference
There is a preference of parents to have a son over a daughter in many countries. This can be observed through sex ratios of children in various countries. Although biologically the sex ratio of children is around 95 girls to every 100 boys, this number generally evens out due to the higher infant mortality rate of boy infants. Scholars argue that the expected birth sex ratio in a normal population is in the range of 103 to 107 males to females at birth.However, in a number of countries of South Asia, East Asia and the Caucasus, the sex ratio of children is severely distorted. The problem is particularly severe in China and India. The preference for sons over daughters can be connected to a number of reasons. In these countries, it is argued that son preference is linked to factors including economics, religion, and culture. Having a son ensures that families are more economically secure by not having to provide dowry payments, but rather being on the receiving end of this practice. In China, the one child policy has contributed to the sex imbalance, while the dowry system in India is responsible for a strong son preference. Furthermore, in countries where there are discriminatory practices regarding women inheriting, owning, or controlling land by law, having a son ensures that the family will not have to worry about the legal aftermath if something were to happen to them. It can also be argued that parents in these countries are aware of the potential hardship their daughter would have to endure in her lifetime, and therefore prefer to have a son in order not to see their daughter endure such difficulties. Many times this son preference results in female foeticide and pre-natal sex selection.
Methods
Pre-implantation
Two major types of pre-implantation methods can be used for social sex selection. Both of them are based on actively rendering the second sex chromosome to be either a Y chromosome, or an X chromosome.The Ericsson method
The Ericsson method, first applied in a clinical setting in the 1970s by Dr. Ronald J. Ericsson, uses higher concentrations of sperm of the desired sex to increase the likelihood of conceiving that sex.When used to increase the likelihood of a female child, studies have resulted in between 70% and 80% female children.
When used to increase the likelihood of a male child, studies have resulted in between 50% and 75% male children.
Currently, approximately 50 gender selection centers in the United States use the Ericsson Method for artificial gender selection.
The Ericsson method separates male and female sperm by passing them through a column filled with blood protein, human serum albumin. As the sperms enter the human serum albumin, the differences in mass between the X and Y chromosomes manifest as the lighter male sperms push deeper into the protein than the females dragged down by the weight of the extra "leg" of the X sex chromosome. This tiny difference creates separate layers of concentrated male and female sperm. The layers of gender-selected sperm are of higher concentrations but not pure. This lack of purity explains the 30% chance of gender selection failure of the Ericsson method.
IVF/PGD technique
After ovarian stimulation, multiple eggs are removed from the mother. The eggs are fertilized in the laboratory using the father's sperm in a technique called in vitro fertilization. "In vitro" is Latin for "within glass". Fertilized eggs are called embryos. As the embryos develop through mitosis, they are separated by sex. Embryos of the desired sex are implanted back in the mother's uterus.Prior to fertilization with IVF, the fertilized eggs can be genetically biopsied with preimplantation genetic diagnosis to increase fertilization success. Once an embryo grows to a 6-8 cell size, a small laser incision in the egg membrane allows safe removal of one of the cells. Every cell in the embryo contains an identical copy of the genome of the entire person. Removal of one of these cells does not harm the developing embryo. A Geneticist then studies the chromosomes in the extracted cells for genetic defects and for a definite analysis of the embryo's sex. Embryos of the desired sex and with acceptable genetics are then placed back into the mother.
The IVF/PGD technique is favored over the Ericsson method because of the stricter control of the sex of the offspring in the laboratory. Since only embryos of the desired sex are transferred to the mother, IVF/PGD avoids the small likelihood present in the Ericsson method of an undesired sperm fertilizing the egg. Sex selection success rates for IVF/PGD are very high. The technique is recommended for couples who will not accept a child of the undesired sex.
Timing methods
Timing methods aim to affect the sex ratio of the resultant children by having sexual intercourse at specific times as related to ovulation. Studies have not been consistent about whether timing methods have any influence on the sex of the baby, with some showing no correlation and others showing just the opposite.- The Shettles method, first formally theorized in the 1960s by Landrum B. Shettles, proposes that sperm containing the X chromosome are more resilient than sperm containing the Y chromosome. The method advocates intercourse two to four days prior to ovulation. By the time ovulation occurs, the cervix should contain a higher concentration of female sperm still capable of fertilization. Intercourse close to ovulation, on the other hand, should increase the chances of conceiving a boy since the concentration of Y sperm will be higher at the height of the menstrual cycle.
- The Whelan method is an "intercourse timing" method that advocates the opposite of the Shettles method. The Whelan method suggests intercourse four to six days prior to ovulation to increase the likelihood of fertilization by male sperm.
Sperm sorting