Astrology is based on the positions of the planets when you take your first breath(or cry) at birth. That's when the air comes into your lungs and body and fixes your genetic code according to the astrological planetary pattern of that moment. That planetary pattern(which includes your Sun, Moon, Asc, MC, and everything else) remains with you until your death, influencing your personality, looks, relationships, and lifestyle.

What about conception, and your mom's or dad's placements while you are still in the womb? Certainly these must have an effect as well. They do, but in an indirect sense. They are not part of your "official" chart which is inprinted on you when you separate from your mother and become an independent being. Nevertheless, they will impact you in a strong way.

Your conception chart, for example, is timed(by you or your higher guides), to produce the desired pattern at birth. The interval between your conception and birth is usually 9 solar months or 10 lunar months(same) or 272/3 days. Some intervals are shorter or longer but this is the norm or average.

To discover your conception date go back 272 days(average) until you come to the Moon being in the same or opposite sign as your natal Ascendant. The Sun will always be in square and the Moon will often be the same as one of your parent's Moons. The transiting Moon sign or its opposite at conception being the same(sign) as the Moon sign at your birth is known as the Trutine of Hermes in astrology. Also, the Ascendant or its opposite at conception becomes the Moon or its opposite at birth. This narrows down the time of conception. This formula is not bullet proof but is surprisingly accurate.

The planetary positions at conception are used as a basis for launching the birth and may have added influence for the native, at least in the biological sense. Perhaps more revealing are the parents' planetary placements and their effect on the developing fetus. Also those of other people constantly around the mother during pregnancy. The embryo is highly sensitive not only to the lights and sounds around it but to the vibratory influences of the parents' astrological placements.

In addition to its own past or karmic baggage, the fetus must deal with its primary current external influence, namely its parents, which are signified in astrology by the MC/IC axis and any planets therein. First and foremost are the planetary placements of the mother(usually the MC), followed by those of the father(usually the IC). Note down the natal planetary placements of both parents and see how they crop up in your current relationships, or how they affect you by transit. You will be especially sensitive to these placements(the sign position is sufficient) whether it be in your relationships(synastry) or your daily life(transits).

The act of birth or exit from the womb can be pleasant, neutral, or even traumatic for the native, and can have an important effect on the native's general attitude towards life, or even his or her sexual life. In fact, the birth act or coming out through the canal can be considered the first sex act and the basis for all our forthcoming acts. The desire for sex is often the desire to reenter the comfort and security of the mother's womb.

If you are a man, your mom's(or dad's) masculine planets(Sun, Mars, etc) will play an important part in defining or expressing your masculinity, and the feminine placements(Moon, Venus, etc) your femininity. Use the planets up to Saturn. The outermost invisible planets do not figure much here. When you come across people with your mom's or dad's personal planetary placements, you may be triggerred on a subconcious level to act out your masculinity and femininity.

Prenatal astrology is a fascinating study that has great psychological implications. Together, astrology, psychology, and science and mysticism would make unbeatable combinations in unraveling the human psyche.