The bankrupt A. H. Robins Co. said yesterday that it had net earnings of $8.3 million in the second quarter, a 56 percent rise over the $5.3 million in the same period last year. Net earnings per share were 34 cents, up 12 cents.

The Richmond company said the earnings gain reflected the absence of an after-tax $8.7 million charge in 1985 resulting from litigation expenses not covered by the reserve fund set up to resolve lawsuits filed by users of the Dalkon Shield intrauterine contraceptive device.

Payouts resulting from the litigation were frozen when Robins filed for Chapter 11 protection on Aug. 21. In the three months ended June 30, after-tax Chapter 11 costs reduced the gain in net earnings by $1.6 million.

Second-quarter sales were $172.6 million, up 5 percent over the corresponding period of 1985, while operating earnings declined 18 percent to $20.8 million.

For the first six months of 1986 as compared with the first half of 1985, net earnings were $30.7 million, down 13 percent, and net earnings per share were $1.27, down 17 cents.

Chapter 11 costs lowered net earnings by $8.7 million after taxes, but, the company said, the reduction was partly offset by an extraordinary gain of $8.5 million "representing recognition of additional deferred tax benefits from the Dalkon Shield reserve. Adjusted for these items, net earnings for the first six months of 1986 declined 7 percent."

Sales in the first half were $364 million, up 10 percent, and operating earnings were $63.3 million, down 2 percent.