What little I've scrounged about implants is that the timing is what is critical.  In other words, the longer you wait post partum, the less effect on lactation.  4 weeks was probably too soon and did affect lactation.  Her current choices - supplement and watch lactation dwindle away, or  remove implant and use other contraception (like condoms).  What I've read seems to be that ob/gyns are too eager to get contraception going, don't rely on effect of lactation amenorrhea, especially in early weeks before intercourse resumed.   From what I've read duration of lactation is affected by early use of implants, but not later (8 weeks PP).  The ob/gyn premise is that they won't come back for implants at  8 weeks so we'd better use them early, so what if it affects lactation duration.  We also know that less than 2 years interval between births is hard on the woman's body, so I get their reasoning.  They don't want to see her at 8 weeks pp and pg!  
 
Hopefully someone on list has a better grasp on this. I'm just opinionated :-) Pat in SNJ

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