I've never read that women being 'forced' by male relatives to abort female fetuses is thought to be a major contributor to skewed sex ratios at birth in the countries currently showing the worst incidence of this problem--Armenia, Georgia, South Korea, India and China. Although, I'll admit I know almost nothing about the situation in the Transcaucasus. In Asia, severely skewed at-birth sex ratios (resulting from sex-selective abortion) are broadly associated with moderately-poor through to upper-middle-class people in the 'developing,' middle-tier countries (and their subregions of the same description)--as opposed to very poor people and/or 'underdeveloped' countries, who as anitram and Lies pointed out can't afford the ultrasound testing involved anyway. So basically, these are people who can afford access to modern medical technology and are comfortable using it, yet retain a 'traditional' mindset when it comes to family expectations--daughters will be married off and moved into their husbands' homes at a fairly young age, with a hefty dowry being paid to the husband's parents, and from there on out contribute nothing to their families of birth; sons may also marry fairly young, but in their case you get the dowry, their wives move into your household thus providing 'household help,' the sons carry on the family business, and finally it's the sons' expected duty to provide for you in old age (keep in mind, these countries are usually altogether lacking in 'eldercare systems' as we know them). So, there are complex traditional family support systems driving this preference for sons--daughters mean a net financial drain for the family, whereas sons offer net financial gain; it's not a simple question of abstract, reflexive 'taboos' against girls, and mothers are just as likely as their husbands to dread the prospect of bearing only daughters. India, China and South Korea have all passed laws banning the use of ultrasounds to determine sex, and it's illegal for doctors to report those results to their patients; but, like the anti-dowry laws that preceded them, these laws are poorly enforced (and hard to enforce), and the reality is that 'everyone knows' where you can find a doctor who'll happily offer an ultrasound-plus-abortion package for (at least in India) as little as $80. While that's still a lot of money to poorer and lower-middle-class couples, many of them will make the calculation that it's better to bite the bullet now and spare themselves far greater financial burdens later. South Korea has had some success bringing down their sex ratio (in the early '90s it hit 1.2 : 1, which I think was the highest at-birth sex ratio ever recorded for an entire country) though a combination of 'public education', enhanced law enforcement, and various incentives to encourage greater educational attainment and economic self-sufficiency for women; India and China are in the process of developing and deploying similar measures in their worst-afflicted regions, but they've a long way to go yet, and most demographers expect their sex ratios will continue to worsen for a while--both are currently at around 1.12--before they get better. (Biologically speaking, the at-birth 'norm' for humans ranges from roughly 1.03 - 1.07.) Regardless, it's extremely unlikely that humanitarian foreign aid could have any significant effects on this problem one way or the other.
As far as the relationship between abortion and adoption rates here in the US goes--it's actually almost certainly not true that blanket criminalization of abortion would mean a glut of infants in the foster care system. The infant relinquishment rate has held steady at around 13,000 infants per year for several decades now, despite abortion rates, net birthrates and single motherhood rates having fluctuated considerably during that same time period. And infants are almost always successfully placed for adoption within several months, maximum; it's the swelling numbers of older children in the foster care system that's the problem: most prospective adoptive parents strongly prefer a baby, while few are interested in, say, a 9-year-old with 'developmental issues' resulting from neglect or abuse in his or her birth family. Bottom line is, the data simply don't support the assumption that reducing abortion in itself means more women choosing to give up their babies for adoption--on the contrary, it seems much more likely that criminalizing abortion would only leave us with far more single mothers than we already have; that very few women would choose to relinquish their infants if they're going to have to go through carrying and bearing them in the first place.