Is it sinful to support abortion when a woman has serious physical complications of pregnancy?

Recently a friend asked whether it is ever 'okay'  to murder a baby by abortion. (in other words, she wanted to know whether it was allowable and not sinful, to kill an infant when the mother is gravely ill.  My friend asked about life threatening complications of continuing a pregnancy and wondered if there were circumstances that allowed for murder of a pre-born child. She humbly admitted that she was fearful that if this ever happened to her own daughter, she would be tempted to allow doctors to kill the baby. Without getting into a whole lot of specifics for many various circumstances and medical threats of pregnancy, this is my answer:

We can't play the 'what if' game. "You shall not murder" trumps the temptation for us to give in to taking innocent life. We have to trust the Lord.

Thou wilt keep him in perfect peace, whose mind is stayed on Thee:
because he trusts in Thee.
Trust in the LORD forever, for the LORD GOD is an everlasting Rock.
Isaiah 26:3-4

 Do not be anxious about anything,
but in everything by prayer and supplication with thanksgiving let your requests be made known to God. And the peace of God, which surpasses all understanding, will guard your hearts and your minds in Christ Jesus.
 ~ Philippians 4:6-7

Trust in Him at all times, O people;
pour out your hearts to Him, for God is our refuge.
Selah.
Psalm 62:8

 Trust in the Lord with all your heart,
and do not lean on your own understanding.
 In all your ways acknowledge Him,and He will make straight your paths.
Proverbs 3:5 & 6

 The sixth commandment gives us the holy mandate. We must always press for protecting a person from harm, both mother and baby. Loving (and preferring) our neighbor as much as we love (and prefer) ourselves must include loving (and preferring) the pre-born person as ourselves as well.

One of the ways that we are to love mothers facing serious diagnosis is to walk with them as their doctors care for them until the infant is viable and labor can be safely induced. We may very well need to provide practical, physical, emotional and spiritual help to her entire family. Physicians prefer to wait til 30 weeks gestation to induce labor, but children can survive at 24 weeks. Even as early as 22 weeks.  That's the short answer.