They say levels of a protein called Shh need to remain largely unchanged in a developing fetus for the palate to develop correctly.

VOA: special.2009.12.22

For example, genes direct formation of the fetus's brain at set times in a woman's pregnancy.

VOA: special.2010.03.23

What if the fetus is found severely affected by a faulty gene?

VOA: special.2010.03.23