Timing may be important for couples experiencing secondary infertility. “Birth spacing” refers to planning the ideal interval between pregnancies. Along with thinking about how far apart you want your kids to be in age, you need to think about hormone balance. It takes time after childbirth for your nutritional status to improve enough to support another pregnancy. It takes time for your body to reestablish hormone balance as well. But if you wait too long, your reproductive hormones may fall out of balance. A recent analysis of 67 studies looking at the outcomes of more than 11 million pregnancies demonstrated that the ideal interval between pregnancies is between 18 months and 6 years. Waiting fewer than 18 months resulted in a much higher chance of preterm birth or having a baby with low birth weight. Women that waited less than 6 months also had a higher risk of miscarriage. Couples, especially those who remarry, might want to keep the 6 year mark in mind when planning to expand their family together.
From PERFECT HORMONE BALANCE FOR FERTILITY[u1] : Book Excerpt: P. 16