From my astrological experience, it is found that the 5th house governs pregnancy and 2nd house supports the 5th house whereas the Trik Houses 6th, 8th, 12th Houses govern abortion. Many causes have been given for abortion or miscarriage like undeveloped uterus, acute illness, sudden emotional feelings.
Delivery of a child can be predicted counting nine rotations of the Nakshatras from the Nakshatra of Conception.
Normally abortion occurs in the second or third month, whereas miscarriage in the 4th month. But the 8th month is also equally dangerous as it is controlled by the malefic planet Saturn
Main Factors To Be Judged For Abortion
1) Nature of Sign in the 5th House
2) Nature and Strength of the Planets in the 5th House.
3) Position posting and strength of Lord of the 5th House.
4) Aspects on the 5th House and Lord of the 5th House.
5) Association of the 5th House with TRIK Houses.
Dasha of Rahu, Mars, Ketu and also trasit of Mars, Ketu, Neptune and Saturn are harmful to the native.
An expert astrology student can warn the native about which period is dangerous for conception and delivery of a Child.