influencing sex of child

  Okay, so, I'm embarrassed to even ask, but are there any strategies I can
  employ to tilt the odds my way if my husband and I want to conceive a girl?
  Our first child is a boy, and we love him dearly, but we'd love to have a
  girl as well.
  Thanks!
  Ellen
Dear Ellen:
There is no scientifically validated method to select the sex of a baby prior to conception.
A generation-plus ago, Landrum Shettles authored a book on sex selection: he promoted position during intercourse, timing of coitus relative to ovulation, and changing the vaginal pH. The principle behind all of these ideas is that the Y-bearing (male) sperm swims faster and by a rear-entry (knees to chest) position (gravity), close to ovulation, and basic pH (baking soda) to expedite swimming, the Y-sperm are assisted in getting to the egg first.
More recently, Erickson has promoted separating the sperms using a laboratory column method (Like sieving different sizes of objects) and doing artificial insemination with the sperms of interest. Other laboratory techniques using light beams to "short cells"; electromagnetic fields; chemicals of different densities have all been tried. Healthcare has a motive: there are serious, hereditable conditions that only occur in one sex, and an effective selection method would save couples the agony of selecting during pregnancy.
Since you have had only one child, we have no reason to believe your odds are different than 50/50. When couples have several children of the same sex, it turn out the husband is more likely to develop more of the X-bearing or Y-bearing sperm, thereby tipping the balance toward one sex.
If you decide to do the vinegar douche, 1 tsp of white vinegar in 1 cup (8 ounces) of warm tap water. Wash the vagina up to 30 minutes before intercourse. This may change the efficiency of vaginal lubrication. Do not use more often than every other day and a maximum of 3 times in one week. Stronger solutions will cause serious irritation.
For those who are going to try the baking soda, 1 level tsp in 2 cups (16 ounces) of warm tap water. This solution predisposes to some infections (the vagina is normally acidic):only use twice in one week close to ovulation as shown by past temperature records or an ovulation detection kit.
Douches can be delivered with a bulb syringe or a bag. If one uses the bulb syringe, do not squeeze so hard that it becomes a jet of fluid: gentle is the message. If one uses a reservoir bag, lie in a tub of warm water, hang the bag on the shower head, and allow the fluid to bathe the vagina.
This material is provided for general information purposes and is not a medical consultation. If you have specific questions, contact your physician.