Hi,
As a Latation Conusltant and a mom who nursed through a pregnancy I can offer both points of view.
As an LC nursing through a pregnancy is rarely an issue unless mom has a history of miscarriage due to uterine stimulation. You are 4 wks along, you have a history of a irritable contractions. The issue here (re: the contractions) is would nursing right now cause a problem? Not sure. It might - but then again it might now. You could wean cold-turkey (not reccommended!) and still miscarry as 25% of all pregnancies spontaneously miscarry (I believ that is the perctenage). You could continue to nurse and be fine.
Weaning cold turkey is not reccommended for several reasons - Your daughter is not ready. It could be emotionally traumatic for her. Are you ready to trade her needs in for a 4 wk-old pregnancy? Weaning cold turkey will also put you at risk for engorgement and mastitis. NOT fun!
As the pregnancy progresses your milk supply will begin to dry up on its own - that is a natural part of the process. As the estrogen levels increase, the prolactin levels drop. The body stops producing milk as it has been in order to put its energies towards the new pregnancy. Your daughter may well wean herself due to lack of milk. Sometime kids will nurse through the pregnancy (as my 2nd son did) and then you can tandem nurse - a whole new adventure!
As an LC I reccommend listening to your gut - do your research and make a choice that is best for you and your daughter.
It is a tough choice - my suggestion as a mom is to stick with the baby who is already here - continue to meet her needs. I had a pregnancy when my 2nd sone was about 14 months old. I was given the same conflicting advice as you. I chose to keep nursing as it was so very importnat to him in SO many ways (he was still refusing solids for one). I miscarried at 8 wks. Had I quit nursing, we would have lost so much. He would have been emotionally traumatised and quiet honestly so would I. Several family memebers blamed the nursing for the miscarriage but they were wrong. It was just something that happened - that old 25%... When he was 18 months old I got pregnant again and carried to term. He nursed through the pregnancy (owie! nipples really tender!) and was a big help when my milk came in after his little brother was born. We tandem nursed for about 9 months. Because I chose NOT to wean for a that first preg. I lost, we nursed for 3 yrs and 2 months - not just 14 months...
Think about it...only you can make the final decision. It can be confusing - sometimes we have to look at what is in front of us right now and put that first...and sometimes not. :)
Good luck!
Warmly,
J. Simpson, IBCLC, CIIM