Developing Fetus Problems

During the embryonic period (the first 8 weeks of the baby's growth), the embryo is most susceptible to factors that can interfere with its development. Most malformations originate during this period.

Some things that have a bad effect (are teratogenic) at one point in pregnancy are safe at other times: rubella, for example. The most critical period is the first 13 weeks. If the fetus is infected with rubella during the 1 st trimester, heart defects often occur. Infection later can be less serious for the fetus. The box below shows critical periods of fetal development. 

Maternal Medication Use
Some medications a pregnant woman takes can harm a developing fetus; others are safe at any time during pregnancy. Still others are safe for one part of pregnancy but not advised for another. It's best to avoid medications during pregnancy unless you discuss them with your doctor first.

PREMATURE BIRTH

It is hard to believe, but today a baby born at only 25 weeks' gestation may survive. Some of the greatest advances in medicine have been in the care of premature babies. Because of advances in technology, fewer than 10 deaths per 1,000 are reported in premature births.
However, babies born extremely early are in the hospital a long time and often have serious problems. Physical and mental handicaps are more common in babies born too prematurely. The average hospital stay for a premature baby can range from 50 days to more than 100 days. The cost is extremely high; a stay of 100 days can cost $200,000 or more.