Pretty much right on Hannibal...
If the guy makes enough sperm to get the woman pregnant, pretty much no other effect.
For the woman, on the other hand, the hormonal and chemical enviornment in which the fetus develops is very important. Remeber that women do produce a certain amount of testosterone naturally, though. 4 months out should not be to bad. The female reproductive system develops between 6 and 8 weeks of pregnancy (post-fertilization, so subtract 2 weeks from how many weeks your doctor tells you- for example, "8 weeks" gestational age is really 6 weeks post-fertilization or "fetal age".)
At 7 weeks (5 weeks fetal age), the gonads first appear but are not populated by primordial germ cells until a week later, when they become the sex cords. These tend to be affected by the presence of a Y chromosome rather than the hormonal mileu present. The presence of a Y chromosome (male fetus) causes the gonads/sex cords to differentiate the seminiferous tubules into testes, which in turn produce testosterone and cause masculinization of the heretofore undifferentiated external genitalia.
The genital ducts (2 types, Mullerian and Wolffian) develop in BOTHsexes. It is the presence of 2 hormones produced by the fetal testes which causes one of the two genital ducts to differentiate into either male or female reproductive organs by causing the other type to REGRESS. These are NOT androgen-based but are affected by testosterone, which stimulates the production of MIF (Mullerian-INHIBITING Factor) and ABP (Androgen Binding Protein). MIF causes REGRESSION of the Mullerian ducts, and allows differentiation of the Wolffian ducts into the male genital structures. ABP in some manner binds Testosterone and perhaps DHT within the Wolffian ducts and permits them to diffentiation by carrying these androgens to their target tissues. The ovaries have not been shown to produce significant amount of anything and their role is thought to be non-existant at this stage of development.
The external genitalia begin developing at 6weeks. It is the presence of DHT (a metabolite of testosterone) which causes them to fuse and develop into male genitalia. The testes do not produce testosterone until week 8. Then they can affect the gonads and external genitalia as described above.
What this all means is that, (as Sassy correctly noted), Adrenal Genital Syndrome is the main concern for preganant female steroid users (which is designed to increase circulating levels of androgens- mainly testosterone, DHT, and DHEA). The primary effects of AGS is masculinization of a female fetus, usually limited to the external genitalia only. In extreme cases, the internal (reproductive) organs may also be affected if the exposure is at the right (wrong) time, but this would probably require extremely high circulating levels of androgens.
So if you're having a boy, no real worries. If it's a girl, you'll just have to wait and see but, given the scenario here, the effects are likely to be none to minimal (clitoral hypertrophy, labial fusion) and operable with preservation of full fertility. Also remember that current female gear such as Oxandrin tends to be minimally androgenic.
That'll be $50.
-babydoc