HACKENSACK, N.J. (AP) _ Surrogate mother Mary Beth Whitehead's out-of-wedlock pregnancy will put further stress on Baby M, says the child's guardian, who now recommends the two be kept apart.

Lawyer Lorraine Abraham has changed her recommendation that Mrs. Whitehead be allowed to visit the baby, legally known as Melissa Stern, after five years, according to papers filed with the state Supreme Court.

Ms. Abraham says the two should not be reunited until Baby M reaches maturity.

''The introduction of a half-sibling into this already difficult situation will create even greater stress,'' Ms. Abraham said in court papers. ''It is difficult to imagine that Melissa will benefit from the stress and conflict.''

Ms. Abraham said in the filing that Mrs. Whitehead, separated from her husband since August, is pregnant by a man she identified only as Dean.

Mrs. Whitehead is asking the New Jersey Supreme Court to overturn the March 31 ruling that stripped her of her parental rights to Baby M and granted custody of the child to her father, William Stern, and his wife, Elizabeth.

Mrs. Whitehead sparked the legal battle after reneging on a $10,000 contract to bear the Sterns a child by being artificially inseminated with Stern's sperm.

The emotional court battle launched a worldwide debate on surrogate motherhood.

The state high court heard oral arguments on the case in September, but has not indicated when it will rule. It has allowed Mrs. Whitehead to visit the baby once a week for two hours in a county home for troubled youths.

It was there, Ms. Abraham said in court papers, that on Oct. 27 Mrs. Whitehead told workers about her latest pregnancy.

Julia Wiggins, a counselor at the home, said in an affidavit that Mrs. Whitehead told her she ''had been pregnant for two months.''

Ms. Abraham wrote, ''Regretfully, I must point out that Mrs. Whitehead's action evidences the impulsivity, narcissism and lack of mature judgment the mental health experts testified to at trial.''

A woman who answered the telephone Tuesday at an East Brunswick condominium in which Mrs. Whitehead has been living said Mrs. Whitehead would not comment.

Mrs. Whitehead's lawyer, Harold Cassidy, did not return telephone calls Tuesday.

June Whitehead, Mrs. Whitehead's mother-in-law, said Tuesday her daughter- in-law is living with a New York City accountant.

Gary Skoloff, lawyer for the Sterns, said an out-of-wedlock pregnancy could be a factor when the Supreme Court rules on custody of Baby M and visitation rights.

Ms. Abraham has refused to comment since she filed her papers.