Abstract: A method and composition are provided for extending the gestation period of a sow so as to increase the live birth and survival rates of a swine litter without adversely affecting the sow. The method includes the step of administering an effective dosage of estrogen to the sow 21/2-7 days prior to the end of the expected gestation period for the sow. The composition administered includes from 0.5-10 mg of an estrogen selected from a group consisting of estradiol benzoate, estradiol valerate, estrone, estradiol 17.beta. and effective mixtures thereof. The composition is adapted for administration parenterally by including a carrier such as corn oil. A method is also provided for synchronizing farrowing in a herd of swine bred following synchronized weaning so as to shorten the target period during which all the sows of the herd begin farrowing.