My husband and I have been discussing lately the "correct" thing to do in terms of family planning-since I am now four months post-partum and these things do happen :)  I have been studying it, and want to present some of my conclusions. 

Our biggest questions are:

1.  Can we provide for a larger family financially?
         God answers:  Deuteronomy 28, the fruit of your womb will be blessed.  The Lord will grant you abundant prosperity in the fruit of your womb.
         My answers:  God clearly states here and elsewhere that God provides for the families and blesses you for your children, but...

2.  Does God say how many children you need? Can people have different "quiver fulls?"
       God answers:  Psalm 127, like arrows in the hands of a warrior, so are the sons born in one's youth.
         My answers:  Paraphrasing someone else, if I were in battle (a warrior) would I only want 3 or 4 arrows, or would I want as many as possible?  In battle would you EVER choose to limit your arrows or continue trying to procure more?  So therefore, I believe God wants you to have as many children as possible..but

3.  this is old testament, what does the new testament say?
        God answers:  Matthew 18:5  Whoever a child in my name welcomes me.
         My answers:  receiving a child is like receiving God, also in thought people may complain about pregnancies, but once the child is here it is always a blessing.  also people never regret having too many children on death beds, but often regret not having enough...but

4.  What does God say about natural family planning or barrier methods or chemical birth controls?
      God answers:  1 Cor. 7 (paraphrased), a couple should only be apart for periods of prayer and fasting with consent, also  Malachi 2:15  In flesh and spirit they (man and wife) are his.  And why one?  Because he was seeking Godly offspring.
      My answers:  God created sex to make babies!  He also made it for our pleasure, but I also believe there are other benefits.  Scientifically semen is linked to acting as an anti-depressant in women-if you use barriers and don't recieve the semen  you are losing that benefit, and I wonder what else?  Chemical birth controls are known to prevent the fertilized egg from attatching to the womb, I believe this to be an abortion and won't use them.    Natural family planning is still a big question for me but here is what I have so far.  In 1 Cor. 7, God prioritized sex as a greater need than food!  it is a top priority for both partners.  Keeping this in mind, did God intend the stress of counting, temperature taking, charting and everything else involved to diminish this act?  Also is it right for men and women to abstain for the purpose of not making a child when that is what sex is for?  However, God did create the cycle of fertilization.  One final thought, in Leviticus God wrote several explicit laws about sex-not having sex during a menstrual cycle being one.  Seeing as he created sex and the cycles don't you think he would have mentioned something if he had intended the Israelites to use NFP?  He did just the opposite, he encouraged procreating and blessed them for it!  Vasectomies are linked to prostate cancer, and having your tubes tied is known to reduce sex drive (causes problems if sex is a duty) and other hormonal changes and is not reccomended. 

Finally, God said to trust in him and not build your  own house(Psalm 127 and Prov. 3:5) and if we trust him with our schooling decisions, nutritional decisions, financial decisions, why wouldn't we trust him and not our own sense of "what is right" for our family size? 

I think the conclusion I have drawn is that I should trust God for my family size, but the decision is ultimately my husbands.  God will not convict one of us, and it is not a sin for me to obey my husband which is my highest calling.  This also makes me realize I need to care for myself and my family so I am ready for what God gives me (the parable of the virgins with the oil comes to mind now) so my prayer is my husband will make a wise decision and God will help me as I continue my growth as a wife and mom.