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Preimplantation Genetic Diagnosis and Gender Selection

לכבוד מורנו הגאב׳ד ורבנים המכובדים שליט״א

Pre-implantation genetic diagnosis (PGD) is available to couples that are at risk of having a child with a specific genetic or chromosome disorder, such as cystic fibrosis, sickle cell disease or Huntington’s disease. The fertilised embryos develop for three days and then one or two cells are removed from each embryo. The genetic material (DNA and chromosomes) from the cells are tested for the known disorder in the family. Up to two unaffected embryos are then transferred into the uterus and the unwanted ones discarded.

Some genetic diseases, such as Duchenne muscular dystrophy, are disorders which affect males but not females. In this case the cells are examined to find out the embryo’s gender and only female embryos are transferred to the womb. In gender selection using IVF and PGD, embryos are created from the couple’s eggs and sperm . On the third day after fertilization, when embryos have reached 6- to 8-cells, one of the cells is removed from the embryo, to be analyzed for its chromosomal makeup. This chromosomal analysis allows us to determine whether the embryo is male or female. Then, only the embryos of the desired gender are transferred to the uterus.

An alternative method of determining the gender of a foetus is by an alternative method called sperm sorting. These methods work on the premise that they separate the X and Y-sperm by either centrifugation or flow cytometry. During centrifugation, controlled spinning causes particles in a sample to become sorted into layers according to density of those particles. Sorting separates the more dense X-sperm from the lighter Y-sperm. One half of the sperm normally produced by a healthy male will carry the Y-chromosome producing a male child, and the other half of the sperm will be the X-chromosome producing a female child. By altering the number of one chromosome or the other by separating the layers, one is increasing the chances of producing a child of a specific gender. During sperm sorting, the sperm cells are separated from the seminal fluid, the sperm are concentrated into healthy and motile sperm, abnormal sperm is filtered out, and finally the separation of the X and Y-sperm concentrates the sample to the desired gender. The remaining sample is more likely to result in a successful pregnancy and will increase the odds of the desired gender group.

The only method of sperm sorting that is currently permitted in the UK is flow cytometry, which uses fluorescent dye to separate sperm carrying male chromosomes from those carrying female ones.

1 Since PGD involves the use of only those eggs that we select as “good”, what should be done with the undesired eggs? Can they be destroyed?

2. Can a couple who have only boys or girls utilise gender selection with PGD in order to fulfill the mitzva of p’ru urvu?

3. Can the method of sperm sorting be permitted under any circumstances as some of the unwanted zera will be discarded?

מחכה ומצפה לתשובתכם


1. Unused eggs may be discarded. The embryo outside the womb is in no way a viable pregnancy, and there is no issur involved. This is assuming there is no future use for this couple with this embryo.

2. Children born of IVF are a subject of debate as to whether this is a fullfilment of Pru Urvu. The Rav is of the opinion that this is a fullfilment. Nevertheless there is no obligation at all to engage in such methods to nake sure a boy and girl are born. In no way is this included in the realm of proper hishtadlus. This being for many reasons, among them the health risk and doubtful outcome of such procedures. For  a couple having children naturally, their gender should be left to prayer and Divine Providence.

3. In all forms of permissible sperm removal [from the male] a large excess of sperm is produced, as the needed amount is minicule. Any sperm of possible use in future procedures should be saved. Any sperm taken out permissibly and necessarily, which now has no use, in the Rav’s opinion may be discarded. In fact keeping it frozen for eternity has no benefit as ultimatley it will not be put to use in any way.

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