B5: Sex Prediction and Selection
SEX PREDICTION
Sex prediction also termed as “prenatal sex discernment”. It is the prenatal testing for discerning the sex of a fetus before birth. A sex prediction test is a test done on or by pregnant women to determine the sex of babies.
Methods:
* Maternal Blood Sample to analyze the small amount of fetal DNA that can be found within, it provides the earliest post-implantation test.

* Chorionic Villus Sampling (CVS) and Amniocentesis are two rather invasive testing procedures. These may, in principle, be formed as early as the 8th and 9th week of pregnancy. The difficulty of these tests and the risk of damage to the fetus, potentially resulting in miscarriage or congenital abnormalities (especially when done early during the pregnancy), make them quite rare during the first trimester.
Amniocentesis (also referred to as amniotic fluid test or AFT) is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections, in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for genetic abnormalities. This process can be used for prenatal sex discernment and hence this procedure has legal restrictions in some countries. * Obstetric Ultrasonography, either transvaginally or transabdominally, can check for the sagittal sign as a marker of fetal sex. It can be performed between 65 and 69 days from fertilization (week 12 of gestational age), where it gives a result in 90% of cases.
Applications:
Potential applications of prenatal sex discernment include: * A complement to specific gene testing for monogenic disorders, which can be very useful for genetic diseases with sex linkage, such as, for example, X-linked diseases. In such cases, it may be much easier to exclude the possibility of disease in the child by prenatal sex discernment than to test for any specific sign of the disease itself. * Ability to prepare for any sex-dependent aspects of parenting. * Sex selection, which after pre-implantation genetic diagnosis may be performed by selecting only embryos of the preferred sex, or, after post-implantation methods by performing sex-selective abortion depending on the test result and personal preference. A 2006 survey found that 42 per cent of clinics that offer PGD have provided it for sex selection for non-medical reasons. Nearly half of these clinics perform it only for “family balancing”, which is where a couple with two or more children of one sex desire a child of the other, but half do not restrict sex selection to family balancing. In India, this practice has been used to select only male embryos although this practice is illegal {{PNDT ACT NO. 57 OF 1994}}. Opinions on whether sex selection for non-medical reasons is ethically acceptable differ widely, as exemplified by the fact that the ESHRE Task Force could not formulate a uniform recommendation.
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 birth. It has been marketed under the title family balancing.
Methods:
PRE - IMPLANTATION * 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. The method has a 70-72% success rate for boys and a 69-75% success rate for girls. 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 sperm enter the human serum albumin, the differences in mass between the X and Y chromosomes manifest as the lighter male sperm 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 (IVF). "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 gender are implanted back in the mother's uterus.
Prior to fertilization with IVF, the fertilized eggs can be genetically biopsied with pre-implantation genetic diagnosis(PGD) to increase fertilization success. Once an embryo grows to a 6-8 cell size, a small laser incision in the egg membrane (zona pellucida) 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 gender. 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 offspring gender 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. Gender selection success rates for IVF/PGD are very high. The technique is recommended for couples who will not accept a child of the undesired gender. * 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, but have shown no influence on the sex of the baby. The Shettles method, first formally theorized in the 1960s by Landrum B. Shettles, proposes that sperm containing the X (female) chromosome are more resilient than sperm containing the Y (male) 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 (with most of the male sperm already dead). Intercourse close to ovulation, on the other hand, should increase the chances of conceiving a boy since the concentration of Y sperm is 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 likelihood of fertilization by male sperm. * Sperm sorting
Sperm sorting is an advanced technique that sorts sperm "in vitro" by flow cytometry. This shines a laser at the sperm to distinguish X and Y chromosomes, and can automatically separate the sperm out into different samples. The technology is already in commercial use for animal farming.It is currently being trialed on humans in the US under the trademark MicroSort; it claims a 90% success rate but is still considered experimental by the FDA.
POST -IMPLANTATION
Sex selection after implantation can be performed by prenatal sex discernment, followed by sex-selective abortion of any offspring of the unwanted sex. For prenatal sex discernment, a blood test can be taken from the mother for testing of small amounts of fetal DNA within it, and has been estimated to be reliable more than 98% of the time, as long as the samples are taken after the seventh week of pregnancy.
POST -BIRTH
Sex-selective infanticide - killing children of the unwanted sex. Though illegal in most parts of the world, it is still practiced.
Sex-selective child abandonment - abandoning children of the unwanted sex. Though illegal in most parts of the world, it is still practiced.
Sex-selective adoption - placing children of the unwanted sex up for adoption. Less commonly viewed as a method of social sex selection, adoption affords families that have a gender preference a legal means of choosing offspring of a particular sex.