What is the cause of the disturbance about Helen's birth?

In a letter from Achilles to Charlie, Nov. 4, 1892, Achilles remembers before his younger sister Helen was born his mother Placidia left the farm and stayed away for several weeks at her Aunt Florie's house. Before she left, she was acting strangely, and while she was gone his father sunk into a deep depression. Everything improved once his mother returned home. In an earlier letter of Sept. 9, 1982, he mentions that Helen had blue eyes like the former slave Achilles and resembled him very much. Obviously, I 'm not suggesting that the black Achilles fathered Helen, since he was long since gone to the north. Why did Helen's birth cast such a strange spell over the household? Did I miss some additional information about her?

I actually wondered this too. My only thought was that its possible that being pregnant for Placidia brought back many memories of when she was pregnant and alone on the farmstead, and also possibly brought back memories of how she became pregnant the first time (being raped by Nolan). For Gryffth I thought it was a similar concept, that his wife being pregnant made him remember another time when she had been pregnant by another man and he hadn't been home to protect her.
I don't think that there was ever any doubt about Helen's parentage, I can't be sure but that wasn't the impression I got from the passage.
That passage though in connection with the description of Gryffth after Placidia died (I can't remember if it was Achilles or Charlie) stated that he almost seemed relieved in a small way, that despite his grief it was as if some small weight had been lifted and that he was less moody afterwards.
I think that even though Gryffth and Placidia loved each other and built a wonderful life together, Gryffth was in fact forever haunted by what she had endured while he had been fighting, and its possible that her pregnancies brought up traumatic memories for both of them.

I think she wanted a safe place to give birth to this baby.

I think that she was ambivalent about the birth--it reminded her of the previous incident and pregnancy. She may have been afraid that the baby would bring a strong reaction from her husband..and reawaken his doubts and anger from the past.

But Achilles is older than Helen - that's why he remembers the mysterious emotions around the time of her birth. And there were quite a few other children of the marriage too, although I don't think we're told in what order they were born. That is why I am confused about why the author included these passages. We aren't told about any problems with the other children's births.

The only thing I can think of is that Achilles does state that Helen and Blue Eyes/Achilles were similar in personality and that they both inherited characteristics from their common ancestor, Placidia's father.

I was puzzled by this section also and agree with the other responses. The blue eyes certainly must be significant.

I must admit I didn’t understand this part of the book. I agree with others that the blue eyes have some significance.

I was totally confused by this section of the book and have no explanation. Perhaps the author can be contacted for some insight?

I thought there might have been some friction between Dia and Griff and she wanted some distance.

I too was confused. At first I thought it was just because this brought up for both parents the trauma of Dia's rape and her husband's sense of guilt, but then I realized Helen was not the eldest, so that didn't make as much sense. I agree that the significant clue is how much Helen physically resembled Dia's father and her now absent brother, the former slave Achilles. That likely roused a different kind of grief, her ambivalent love for her father, her anxiety and sense of responsibility for her missing brother; and for the Major, it could have been a painful reminder of the deep flaws of the Southern system he had fought to protect, while failing to protect his own wife.

On another level, I wondered why include this at all, and my best thinking right now is that the author wanted to remind us of the continuing power of our past, how it influences our present, whether we acknowledge it or not. Better to face up to it and work through it, as Dia and the Major did in bringing her and Helen home again.

I took it to mean that Dia's father had relations with a slave and that Dia had black relatives, This was disturbing to Dia as it broke her understanding who her father was. It seems also that Dia also needed time to herself from time to time. Major Hockaday also was not the easiest person to live with.

I'm glad I'm not the only one who has questions about this. I found it very confusing and appreciate everyone's thoughts. I agree that the blue eyes seem significant, but I sure wish the author had clued us in a little more.

I think the author could have given us more information here. When I read it I thought that perhaps Dia had postpartum depression and that is why she remained away so long. As for the blue eyes, how would Griff have known unless he'd seen Helen before his wife and baby came back?