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hormonal effects in newborns

Alternative Names 
normal conditions in a newborn resulting from maternal hormones

Newborns are often born or experience a variety of normal conditions after birth. These conditions include acne, yellowing of the skin known as jaundice, darker pigmentation to the skin and temporary changes in the genitals or breasts. Many of these conditions exist because of the mother's hormones passed to the foetus just before birth or to the infant during breastfeeding.

What is going on in the body? 
During pregnancy, hormones from the mother's bloodstream enter the foetus' body through the placenta. These hormones cause certain conditions that are apparent at birth. In addition, breastfed infants receive maternal hormones in breast milk that may also cause certain conditions that are normal and pose no risk to the baby.

What are the signs and symptoms of the condition? 
The hormones that the foetus is exposed to in the several weeks prior to birth primarily affect the newborn's skin and genitals. For the first 6 to 8 weeks after birth, an infant will often have a rash on his or her face. This rash consists of small, red bumps and "whitehead" like pimples. For this reason, the condition is often referred to as "baby acne." This rash occurs most often on the forehead, cheeks and nose. It can also occur on the upper trunk.

Oestrogen hormones from the mother's body cause breast tissue to enlarge in both boys and girls. This normally occurs late in pregnancy. Beginning at about the 36th week of pregnancy both infant girls and boys begin to develop "breast buds." This is the swelling of breast tissue immediately beneath and around the nipples. At birth these buds are usually about 1/2 to 3/4 inch in diameter and protrude about 1/4 inch. The nipple itself does not become enlarged. At times a small drop of a milk-like secretion may be seen on the infant's nipple. Breast buds may remain swollen for several weeks after birth.

Maternal hormones also affect the pigmentation of the newborn's skin. These hormones mainly affect skin areas that are sensitive to hormones, such as the nipples and genitals. At birth, this skin is darkly pigmented in both boys and girls. This is similar to the effects hormones will have on these areas in puberty. In addition, the hormone exposure in late pregnancy causes baby's genitals to enlarge. However, the size and colour of the genitals returns to normal within a few weeks after birth.

Another condition caused from maternal hormones in some newborn girls is a slight, whitish mucous discharge from the vagina. This discharge is due to a temporary maturation of the mucous-secreting vaginal cells. It too goes away within a few weeks.

Maternal hormones can also affect newborn infants through a condition called "breast milk jaundice." Some mothers produce a hormone in their milk called pregnanediol. This hormone interferes with the liver's ability to metabolise or breakdown a substance called bilirubin. Bilirubin is a by-product of the breakdown of the haemoglobin in red blood cells. Normally, bilirubin is broken down in the liver so that it can be excreted in the urine. If bilirubin does not break down properly, it can accumulate in the blood and other tissues. This causes jaundice, which is a yellowish discolouration of the skin, urine and whites of the eyes. Unless there are other complicating factors, breast milk jaundice is not harmful to the baby. It usually goes away within several weeks. Interrupting breast-feeding for 24 to 48 hours often causes the jaundice to resolve more quickly. However, this is not necessary for the health of the baby.

What are the causes and risks of the condition? 
This condition is caused by the normal concentration of female hormones in the mother's body during late pregnancy and hormones passed through breastfeeding.

How is the condition diagnosed? 
These hormonal effects are often observed during the newborn physical examination or in one of the baby's first of several doctor's visits. Diagnosis is made by looking at the infant. No laboratory tests are indicated. Sometimes a doctor may recommend a blood test to evaluate the bilirubin level if a baby has significant jaundice.

What are the long-term effects of the condition? 
There are usually no long-term effects from the maternal hormones.

What are the treatments for the condition? 
No treatment is needed. These changes are normal and resolve by themselves within a few weeks.

Author: John Wegmann, MD
Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 9/1/2005
Potential conflict of interest information for reviewers available on request

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