When a legal separation is decreed, the court may order payment of such support by one party to the other as may be reasonable, having regard for the circumstances of the parties and the ability of the supported party to engage in gainful employment without interfering with the interests of any minor children in the custody of such party. Orders for support may be modified or revoked for good cause shown upon notice and hearing, except as to amounts accrued prior to date of service of motion to modify, to which date modification may be retroactive. Orders for child support in cases in which a party has applied for services under Title IV-D of the Social Security Act, as amended, shall be reviewed as provided in sections 43-512.12 to 43-512.18.