All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
There is no doubt that the matter of having children is in the Hands of Allaah Alone. It is He Who blesses whomever He wills with male or female children. Allaah says (what means): {To Allaah belongs the dominion of the heavens and the earth; He creates what he wills. He gives to whom He wills female [children], and He gives to whom He wills males. Or He makes them [both] males and females, and He renders whom He wills barren. Indeed, He is Knowing and Competent.}[Quran 42:49-50] Allaah Alone is the Creator and there is no creator besides Him.
Perhaps what they meant is that the mother has a role in the development of the fetus in terms of nutrition and the like, and this is correct as the fetus is affected by the nutrition of the mother and her psychological and health condition. The suckling infant is also affected by it.
There is no harm in reading books and articles about the development of the fetus and the period of pregnancy, and to take from them what is in conformity with Islam and reject what is not founded on a valid foundation or what involves violations to the Sharee‘ah, and to ask those who know about what the person does not know; Allaah says (what means): {So ask the people of the message if you do not know.} [Quran 16:43]
Allaah Knows best.