Breasts and areolas will enlarge and become more tender with pregnancy. The skin of the areola will also usually become darker in color, and Montgomery glands will protrude in preparation for providing lubrication for the skin while an infant is breastfeeding. The changes that occur are due to a hormonal response to prepare for lactogenesis for breastfeeding. Women who are breastfeeding and become pregnant will have a change in their milk back to colostrum, the first milk provided to the infant after delivery, at around 16–18 weeks, and the child may decide to wean as they are not filling with milk. Breastfeeding is not contraindicated in pregnancy.

There is an increase in pelvic blood flow to adapt to the increased need for it between the placenta and the fetus. The uterus will change in size, shape, and position. With the growing fetus inside, the muscle of the uterus stretches, and it becomes an abdominal organ instead of a pelvic organ; this size also helps to determine if the baby is growing at an appropriate rate.

Fundal height is the distance between the public bone and the top of the uterus. It is measured in centimeters. By 20 weeks, the fundal height is approximately at the height of the belly button. From week 24 onwards, the distance typically matches the number of weeks the woman has been pregnant. After week 36, the fundal height starts to decrease and the uterus expands in width.

By the end of the first trimester, the uterus should be felt just above the pubic bone. By 16 weeks, the fundus (top of the uterus) should be palpated at about halfway between the pubic bone and the umbilicus. At 20 weeks, the fundus is palpable at the umbilicus. Beyond 20 weeks, we can correlate the measurement between the pubic bone and the fundus in centimeters with the gestational age in weeks. This is called the fundal height. Discrepancies in the fundal height would necessitate further testing—usually by ultrasound—to determine the cause. As the pregnancy progresses, changes in contractility of the muscle will occur. Known as Braxton Hicks contractions, this tightening of the uterine muscle functions as practice contractions to tone the muscle before birth; these may increase with maternal dehydration or activity.

Due to an increase in estrogen, the cervix will soften; this is called Goodell’s sign. The increased vascularity of the pelvis causes the cervix to have a slightly bluish color; this is called Chadwick’s sign. Initially, there is also a softening of the lower uterine segment due to the increased blood supply just above the cervix; this is known as Hegar’s sign. The cervix is normally around 4 cm thick; thinning of the cervix to less than 2.5 cm as measured by ultrasound could indicate the potential for preterm delivery, and interventions would be taken to prevent this outcome. The cervix may begin to dilate at term, but prior to this, it would indicate preterm labor and delivery.

Due to nausea and vomiting in pregnancy, there is usually little weight gain until after the first trimester. Afterward, women usually catch up with weight gain, and by 20 weeks they should have gained approximately 10 pounds. After that, an average of one-half to one pound a week occurs for a total gain of 25–35 pounds. Individuals who begin pregnancy overweight should gain approximately 15–25 pounds total; those who begin underweight should gain 30–40 pounds.

• Pigment Changes:  Estrogen and progesterone cause hyperpigmentation of areolae, genital skin, axillae, inner thigh, and linea alba (linea nigra). Melasma is a term for the “mask of pregnancy” on the face.

• Vascular Changes: Vasodilation of capillaries causes telangiectasia and palmar erythema. This change can help in thermoregulation by dissipating heat generated by the fetus, increasing the metabolic rate, and allowing thermogenesis of progesterone.

• Connective Tissue Changes:  Estrogen, relaxin, and adrenocorticoids, along with stretching of skin, cause striae gravidarum. There is also an increase in skin tags.

• Sebaceous and Sweat Gland Changes:  Sebaceous glands secrete more to evaporate and dissipate heat due to an increase in thyroid activity, metabolic rate, and fetal-produced heat.

• Hair and Nail Changes:  Increased hair growth occurs due to estrogen; individuals may have transverse grooves in nails, causing brittleness.

The gravid uterus will displace the organs in the gastrointestinal system. This can affect the assessment of the abdomen; specifically of note is the appendix changing position from the right lower quadrant to the right upper quadrant. Progesterone relaxes smooth muscles, so there is a decrease in lower esophageal muscle tone, causing heartburn. Relaxation of the intestines will decrease peristalsis and cause constipation. The gallbladder can also slow and increase the incidence of gallstones. The mouth and gums respond to estrogen and become friable and softer. Some women have ptyalism, which is aggravated if they have nausea and vomiting.

Glucose changes will be discussed later. HCG, as discussed earlier, is the hormone associated with pregnancy and, along with estrogen and progesterone, is produced by the placenta to sustain the pregnancy. Anatomical changes include an increase in the size of the thyroid gland, which will reflect in an increase in the maternal basal metabolic rate. The pituitary gland has a 135% increase, which may cause headaches and visual changes. The pituitary changes function as it is responsible for a 10-fold increase in prolactin to prepare for lactogenesis. Some women may begin to leak colostrum (early breast milk) while pregnant. Oxytocin is produced at the end of pregnancy to begin uterine contractions for labor and also expel breast milk while feeding the infant. Adrenal function increases as pregnancy progresses—aldosterone level increases, and corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) are important in the initiation of labor and sustaining relaxation between contractions.

• Unlike Rh incompatibility, ABO incompatibility does not worsen with each pregnancy. It involves a mother with an O blood type passing anti-A or anti-B antibodies across the placenta to a fetus who has an A, B, or AB blood type. This anemia is not usually so severe as to cause fetal demise.

• Other antibody disorders can affect pregnancy; some are more harmful than others. The severity of symptoms in the fetus depends on the number of antibodies produced by the mother, and titers can be drawn periodically to monitor it.

• For additional information on why antibodies are tested in pregnancy, read:

  • Tapper, L. (2013). Of kell and kings. Links to an external site.O&G Magazine, 15(4).