hi - i'm not a reflexologist, and i'm sure you'll get much better answers from reflexologists on the list. i do pregnancy massage & am currently pregnant myself.
the points i believe you need to avoid are the one on the medial ankle - the uterus point; the lateral distal point on the superior aspect of the smallest toe (i believe this helps to stimulate labour); and perhaps the point on the medial distal superior aspect of the large toe, which may have the same effect.
you may wish to avoid doing anything to stimulate detoxing her liver, particularly as the baby starts accumulating fat in the 3rd trimester.
work done on keeping her calm and relaxed is helpful - is there adrenal work you can do to achieve this? also work on freeing stress from any head points (eg, jaw, mouth), neck and shoulders is v good. she may have trouble sleeping, and any help you can give in that regard is wonderful.
when manipulating joints in which connective tissue is dealt with, be careful and perhaps a little more gentle, as this tissue now has more give than outside of pregnancy, and connective tissue, once stretched, can remain permanently overstretched.
because of the significant increase in blood fluids, her circulatory system must work harder - this can affect her heart. she may have a change in her blood pressure - either hypotension (she may be a bit dizzy when she gets up) or hypertension.
as the pregnancy progresses, and the baby grows, it can decrease the physical space her lungs have in which to expand. aiding in relaxed breathing would be helpful.
her immune system can be slightly depressed, in order that her body does not reject the baby.
as her uterus grows, it may pull on some of the ligaments holding it in place, causing sharp pains around her groin or thighs, or period-like aches & pains.
she may experience leg or foot cramps.
she may find that her breasts are particularly tender or sore.
she may also be experiencing some conditions in pregnancy - some common ones to be aware of include:
digestive difficulties, from constipation [and its associated problems] to reflux, as the hormone relaxin (which works as a relaxing agent on all connective tissue) can cause the large colon's peristaltic movement to slow or work less efficiently, or the esophageal sphincter to relax; it can also cause the gums to bleed more readily.
she may experience nausea and fatigue not only in her first trimester, but throughout her pregnancy. just the fatigue may return in her last trimester.
relaxin may also affect the bladder, as well as its having to cope with increased output, (this increase in output may also affect the kidneys - there is some increase in the possibility of urinary tract infections and/or kidney infections in pregnancy).
relaxin may also cause valves and vein walls to be more slack, resulting in varicose veins. these can sometimes resolve after birth.
other conditions can include water retention (esp in her ankles or wrists [which may manifest as carpal tunnel syndrome or tingling/numbness in the fingers but usually disappears after birth] and hypertension (high blood pressure) which are often indicators of pre-eclampsia - she needs to see her medical advisor about these signs, and perhaps someone more qualified here can advise you on reflexology for this situation, which can become life-threatening for mother and baby if it is left completely untreated.
another condition can be gestational diabetes, which would be diagnosed and managed by her medical advisor.
sometimes thyroid problems can arise in pregnancy. this will be diagnosed and managed by her medical advisor.
she may find herself having sinus problems - it is quite common to be especially mucousy or stuffed up in pregnancy. there are not many high street remedies she can turn to for this.
she may have anaemia - if her blood count is lower than 8/8.5 g/dl, she will have been advised to take iron supplements (which can lead to constipation, or she may choose to receive injections to try to avoid constipation); she may wish to try changing her diet aggressively to ensure greater iron consumption. is there anything you can do to ensure optimal digestive absorption, or something else in regard to anaemia?
a very painful condition is symphysis pubis - the joint which connects the pubic bones in front can be affected by the relaxin, causing the 2 bones to rub against each other. it can be an extremely painful and debilitating condition - is there anything you might be able to do about this?
in the last couple of weeks, if her baby has not yet turned to be head down, there may be something that reflexology can stimulate to encourage the baby to assume this position, which is the best for birthing naturally.
some situations do need to be corrected, but others may arise as a normal part of pregnancy and, while out of what is considered to be the normal range for most people, actually serve a purpose in pregnancy. for example, the pituitary is involved in a various ways throughout the pregnancy, so treating it may be helpful or a hindrance, depending on what balance of complex situations exist in her at the time. treatment will also vary during pregnancy, and during labour and delivery, as well as with each individual pregnancy.
whatever else, she might especially appreciate you working on her lower back/pelvic/sciatic points! easing any stress here will not only soothe immediate aches and pains, but may help the pelvis to relax enough and ease open gently, allowing more room for baby to pass through.
one final note: do not work on her with her lying flat on her back - as the pregnancy progresses, the combined weight of the uterus and all its contents will compress the vena cava, which means that blood flow returning from her legs to her heart will be compromised. she should be sitting up at least at an angle; also you may need to be sure to use a pillow under her knees and/or ankles to help protect those joints.
good luck!