Iiiif I recall correctly, warforged were batch-made, and none were constructed as outwardly female - there were only about three-ish types, at least back in 3.5e. From the Eberron Wiki:



"The warforged have a sexless form and are considered to be mono-gender. The warforged are able to be repaired and modified by artificers or even themselves giving them an endless possibility to their appearances."



Obviously, a construct isn't actually a male or a female, but I see no reason why they can't present as either, depending on their build. I'd have to dig out my books, though.



EDIT: Found it, Monster Manual 3. "Warforged have no physical distinction of gender, and all warforged have a body shape that is basically male. In personality, some warforged seem more masculine or feminine, but different people might judge the same warforged in different ways. The warforged themselves seem wholly unconcerned with matters of gender."