Failure to thrive in the womb
There are 4 main reasons why a fetus fails to grow or be of a normal size in the womb:
- Constitutional – The fetus grows well but is small, because it was meant to be small (typically the parents will be relatively small also).
- Maternal – The mother is unwell or undernourished (the most common reason for being born small and growth restricted).
- Uteroplacental – The placenta fails to establish a good relationship with the uterus (womb). This leads to problems later in the pregnancy, when the growing fetus demands more and more oxygen and other nutrients from the placenta, which cannot deliver. The fetus fails to thrive to thrive and becomes small and growth restricted (IUGR). Ultrasound can reveal the IUGR and assess the condition of the fetus using biophysical assessment and fetal Doppler.
- Fetal – The fetus may have an abnormality that affects its growth, or it may have an infection. Part of the assessment of the IUGR baby is to look for signs of these and other problems.
The management and decision regarding delivery of a small, especially growth restricted fetus, is complex and dealt with on an individual basis (see scanning in the second half of pregnancy).
The relationship between maternal psychosocial factors, and low birth weight and preterm delivery is not fully understood. Negative mood states such as anxiety, depression, and/or hostility, and rejection of the pregnancy were more likely to be associated with low birth weight. Emotional support, counselling and strengthening of the woman’s social network and other efforts to improve self-esteem may help to promote the health of the mother and baby.
If a pregnancy has reached maturity or term, delivery can be considered as a solution to IUGR. If the cervix is favourable induction of labour can be attempted, but if the cervix is unfavourable a Caesarean section may be required.
Pre term IUGR involves a multidisciplinary team, trying to achieve greater maturity for the fetus, but not allowing the fetus to become too compromised before delivery. The final decision is usually taken by the multidisciplinary team looking after the patient.